Neophotonics (NPTN) 10-K 7 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Feb. 28, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	NPTN
Entity Registrant Name	NEOPHOTONICS CORP
Entity Central Index Key	1,227,025
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		46,426,672
Entity Public Float			$ 215,597
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 58,185	$ 78,906
Short-term investments	7,481	12,311
Restricted cash	11,053	2,658
Accounts receivable, net of allowance for doubtful accounts	74,751	67,229
Inventories	52,159	67,301
Assets held for sale	2,971	0
Prepaid expenses and other current assets	26,605	36,235
Total current assets	233,205	264,640
Property, plant and equipment, net	100,090	127,565
Purchased intangible assets, net	3,018	4,294
Goodwill	1,115	1,115
Other long-term assets	3,148	5,339
Total assets	340,576	402,953
Current liabilities:
Accounts payable	58,403	69,017
Notes payable and short-term borrowing	4,795	35,607
Current portion of long-term debt	2,897	6,005
Accrued and other current liabilities	50,288	43,242
Total current liabilities	116,383	153,871
Long-term debt, net of current portion	50,454	40,556
Other noncurrent liabilities	13,499	14,075
Total liabilities	180,336	208,502
Commitments and contingencies (Note 14)
Stockholders’ equity:
Preferred stock, $0.0025 par value, 10,000 shares authorized, no shares issued or outstanding	0	0
Common stock, $0.0025 par value, At December 31, 2018, 46,378 shares issued and outstanding; at December 31, 2017, 44,219 shares issued and outstanding	116	111
Additional paid-in capital	564,722	545,953
Accumulated other comprehensive income (loss)	(7,126)	398
Accumulated deficit	(397,472)	(352,011)
Total stockholders’ equity	160,240	194,451
Total liabilities and stockholders’ equity	$ 340,576	$ 402,953

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (USD per share)	$ 0.0025	$ 0.0025
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (USD per share)	$ 0.0025	$ 0.0025
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	46,378,000	44,219,000
Common stock, shares outstanding (in shares)	46,378,000	44,219,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenue	$ 322,540	$ 292,894	$ 411,423
Cost of goods sold	256,367	231,415	294,290
Gross profit	66,173	61,479	117,133
Operating expenses:
Research and development	53,818	58,287	57,376
Sales and marketing	16,728	17,760	18,595
General and administrative	30,403	34,453	34,409
Amortization of purchased intangible assets	475	472	1,609
Acquisition and asset sale related costs	427	130	2,125
Restructuring charges	3,135	3,934	0
Litigation settlement	2,645	0	0
Loss (gain) on asset sale	200	(2,193)	0
Total operating expenses	107,831	112,843	114,114
Income (loss) from operations	(41,658)	(51,364)	3,019
Interest income	397	198	303
Interest expense	(2,493)	(1,362)	(402)
Other income, net	1,446	104	472
Total interest and other income (expense), net	(650)	(1,060)	373
Income (loss) before income taxes	(42,308)	(52,424)	3,392
Provision for income taxes	(1,329)	(909)	(3,597)
Net loss	$ (43,637)	$ (53,333)	$ (205)
Basic net loss per share (USD per share)	$ (0.97)	$ (1.23)	$ 0
Diluted net loss per share (USD per share)	$ (0.97)	$ (1.23)	$ 0
Weighted average shares used to compute basic net loss per share (in shares)	45,144	43,431	41,798
Weighted average shares used to compute diluted net loss per share (in shares)	45,144	43,431	41,798

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (43,637)	$ (53,333)	$ (205)
Other comprehensive income (loss):
Foreign currency translation adjustments, net of zero tax	(7,464)	8,803	(6,640)
Unrealized gain on available-for-sale securities, net of zero tax	1	17	10
Defined benefit pension plans:
Loss arising during the period	(95)	(32)	(72)
Curtailments, settlements and other	0	0	0
Tax	34	11	24
Total other comprehensive income (loss)	(7,524)	8,799	(6,678)
Comprehensive loss	$ (51,161)	$ (44,534)	$ (6,883)

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustments, tax	$ 0	$ 0	$ 0
Unrealized gains (losses) on available-for-sale securities, tax	$ 0	$ 0	$ 0

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2015		40,986
Beginning balance at Dec. 31, 2015	$ 211,656	$ 102	$ 511,750	$ (1,723)	$ (298,473)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive loss	(6,883)			(6,678)	(205)
Issuance of common stock upon exercise of stock options (in shares)		1,013
Issuance of common stock upon exercise of stock options	3,671	$ 3	3,668
Issuance of common stock under employee stock purchase plan (in shares)		351
Issuance of common stock under employee stock purchase plan	2,779	$ 1	2,778
Issuance of common stock for vested restricted stock units (in shares)		226
Issuance of common stock for vested restricted stock units	0	$ 0	0
Tax withholding related to vesting of restricted stock units (in shares)		(50)
Tax withholding related to vesting of restricted stock units	(615)		(615)
Stock-based compensation costs	14,797		14,797
Ending Balance (in shares) at Dec. 31, 2016		42,526
Ending balance at Dec. 31, 2016	225,405	$ 106	532,378	(8,401)	(298,678)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive loss	(44,534)			8,799	(53,333)
Issuance of common stock upon exercise of stock options (in shares)		665
Issuance of common stock upon exercise of stock options	2,483	$ 2	2,481
Issuance of common stock under employee stock purchase plan (in shares)		349
Issuance of common stock under employee stock purchase plan	2,393	$ 1	2,392
Issuance of common stock for vested restricted stock units (in shares)		806
Issuance of common stock for vested restricted stock units	0	$ 2	(2)
Tax withholding related to vesting of restricted stock units (in shares)		(127)
Tax withholding related to vesting of restricted stock units	(998)		(998)
Stock-based compensation costs	9,702		9,702
Ending Balance (in shares) at Dec. 31, 2017		44,219
Ending balance at Dec. 31, 2017	194,451	$ 111	545,953	398	(352,011)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive loss	(51,161)			(7,524)	(43,637)
Issuance of common stock upon exercise of stock options (in shares)		779
Issuance of common stock upon exercise of stock options	3,422	$ 2	3,420
Issuance of common stock under employee stock purchase plan (in shares)		404
Issuance of common stock under employee stock purchase plan	2,191	$ 1	2,190
Issuance of common stock for vested restricted stock units (in shares)		1,124
Issuance of common stock for vested restricted stock units	0	$ 2	(2)
Tax withholding related to vesting of restricted stock units (in shares)		(148)
Tax withholding related to vesting of restricted stock units	(954)		(954)
Stock-based compensation costs	14,115		14,115
Ending Balance (in shares) at Dec. 31, 2018		46,378
Ending balance at Dec. 31, 2018	$ 160,240	$ 116	$ 564,722	$ (7,126)	$ (397,472)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net loss	$ (43,637)	$ (53,333)	$ (205)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	31,105	28,350	22,400
Stock-based compensation expense	14,142	8,206	17,076
Deferred taxes	(328)	792	(668)
Amortization of investment, debt and other	438	247	159
Loss (gain) on disposal of property and equipment	1,322	(1,746)	185
Loss (gain) on foreign currency hedges	2,220	(2,104)	1,640
Allowance for doubtful accounts	61	577	(382)
Write-down of inventories	6,133	8,349	2,983
Foreign currency remeasurement and other, net	(3,944)	2,583	(2,661)
Asset impairment charges	0	324	0
Change in assets and liabilities:
Accounts receivable	(7,874)	13,166	2,496
Inventories	7,368	(22,347)	(1,332)
Prepaid expenses and other assets	8,162	(11,409)	(11,184)
Accounts payable	(1,411)	(10,874)	23,111
Accrued and other liabilities	5,838	6,452	218
Net cash provided by (used in) operating activities	19,595	(32,767)	53,836
Cash flows from investing activities
Purchase of property, plant and equipment	(14,867)	(47,409)	(51,693)
Proceeds from sale of property, plant and equipment and other assets	32	21,809	179
Purchase of marketable securities	(920)	(52,062)	(82,728)
Proceeds from sale of marketable securities	5,000	52,272	63,841
Proceeds from maturity of marketable securities	750	6,458	23,148
Restricted cash payable related to asset sale	0	0	1,039
Settlement of foreign currency hedges	(1,776)	1,618	(1,599)
Net cash used in investing activities	(11,781)	(17,314)	(47,813)
Cash flows from financing activities
Proceeds from exercise of stock options and issuance of stock under ESPP	5,614	4,893	6,587
Tax withholding on restricted stock units	(954)	(998)	(615)
Payments for public stock offering, net of offering costs	0	(117)	(164)
Proceeds from bank loans	34,305	112,834	95,200
Repayment of bank and acquisition-related loans	(63,040)	(68,492)	(96,119)
Proceeds from issuance of notes payable	7,137	6,621	16,032
Repayment of notes payable	(3,732)	(11,639)	(18,007)
Proceeds from government grants	1,210	0	602
Net cash (used in) provided by financing activities	(19,460)	43,102	3,516
Effect of exchange rates on cash, cash equivalents and restricted cash	(680)	1,958	(1,702)
Net increase (decrease) in cash, cash equivalents and restricted cash	(12,326)	(5,021)	7,837
Cash, cash equivalents, restricted cash and restricted cash equivalents, beginning of period	81,564	86,585	78,748
Cash, cash equivalents, restricted cash and restricted cash equivalents, end of period	69,238	81,564	86,585
Supplemental disclosure of cash flow information:
Cash paid for interest	1,600	732	263
Net cash paid (received) for income taxes	(1,383)	5,388	2,215
Supplemental disclosure of noncash investing and financing activities:
Unpaid deferred offering costs	0	0	117
Decrease (increase) in unpaid property, plant and equipment	8,548	6,072	(13,629)
Capital lease	362	0	0
Asset retirement obligation	$ 0	$ 2,146	$ 0

Summary of significant accounti

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of significant accounting policies	Summary of significant accounting policies Use of estimates The preparation of financial statements in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported revenue and expenses during the reporting period. Significant estimates made by management include: the useful lives of property, plant and equipment and intangible assets as well as future cash flows to be generated by those assets; fair values of identifiable assets acquired and liabilities assumed in business combinations; allowances for doubtful accounts; valuation allowances for deferred tax assets; write off of excess and obsolete inventories; the valuation of the Rusnano payment derivative and the valuations and recognition of stock-based compensation, among others. Actual results could differ from these estimates. Concentration of credit risk and significant customers Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash and cash equivalents and trade accounts receivable. The Company’s investment policy requires cash and cash equivalents to be placed with high-credit quality institutions and limits on the amount of credit risk from any one issuer. The Company performs ongoing credit evaluations of its customers’ financial condition whenever deemed necessary and generally does not require collateral. The Company maintains an allowance for doubtful accounts based upon the expected collectability of all accounts receivable, which takes into consideration an analysis of historical bad debts, specific customer creditworthiness and current economic trends. Customers accounting for more than 10% of our total revenue and revenue from our top five customers for the years ended December 31, 2018, 2017 and 2016 were as follows: Years Ended December 31, 2018 2017 2016 Percent of revenue from customers accounting for 10% or more of total revenue: Huawei Technologies Co., Ltd 46 % 40 % 50 % Ciena Corporation 24 % 16 % 15 % Percent of revenue from top five customers 87 % 78 % 82 % As of December 31, 2018, two customers accounted for approximately 35% and 17% , respectively, of the Company’s total accounts receivable. As of December 31, 2017, three customers accounted for 36% , 14% and 10% of the Company’s total accounts receivable. Restricted cash As a condition of the notes payable lending arrangements and the line of credit facilities, the Company is required to keep a compensating balance at the issuing banks. In addition, the Company also maintained restricted cash in connection with the asset purchase agreement executed in December 2016 (see Note 10), government grants received in advance and cash balances temporarily restricted for regular business operations until a legal dispute is resolved (see Note 14). These balances have been excluded from the Company’s cash and cash equivalents balance and are classified as restricted cash in the Company’s consolidated balance sheets. As of December 31, 2018 and 2017, the amount of restricted cash was $11.1 million and $2.7 million , respectively. Cash, cash equivalents and investments Highly liquid investments with a maturity of 90 days or less at the date of purchase are considered cash equivalents, with the exception of money market funds and commercial paper which are classified as short-term investments. Marketable securities are reported at fair value and are classified as available-for-sale investments in our current assets because they represent investments of cash available for current operations and for strategic reasons. As a result, the Company recorded all its marketable securities in short-term investments regardless of the contractual maturity date of the securities. The Company regularly reviews its investment portfolio to identify and evaluate investments that have indications of possible impairment. Factors considered in determining whether a loss is other-than-temporary include: the length of time and extent to which the fair market value has been lower than the cost basis, the financial condition and near-term prospects of the investee, credit quality, likelihood of recovery, and the Company’s ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in fair market value. Unrealized gains and losses, net of tax, are included in accumulated other comprehensive loss as a separate component of stockholders’ equity on the consolidated balance sheets. The amortization of premiums and discounts on the investments, and realized gains and losses on available-for-sale securities are included in other income, net in the consolidated statements of operations. The Company uses the specific-identification method to determine cost in calculating realized gains and losses upon the sale of its marketable securities. Fair Value Measurements Fair value is defined as the price at which an asset could be exchanged in a current transaction between knowledgeable, willing parties. A liability’s fair value is defined as the amount that would be paid to transfer the liability to a new obligor, not the amount that would be paid to settle the liability with the creditor. Where available, fair value is based on observable market prices or parameters or derived from such prices or parameters. Where observable prices or inputs are not available, valuation models are applied. These valuation techniques involve some level of management estimation and judgment, the degree of which is dependent on the price transparency for the instruments or market and the instruments’ complexity. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative accounting guidance describes a fair value hierarchy based on three levels of inputs that may be used to measure fair value, of which the first two are considered observable and the last is considered unobservable. These levels of inputs are as follows: Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3—Unobservable inputs that reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. For marketable securities measured at fair value using Level 2 inputs, the Company reviews trading activity and pricing for these investments as of the measurement date. When sufficient quoted pricing for identical securities is not available, the Company uses market pricing and other observable market inputs for similar securities obtained from various third party data providers. These inputs either represent quoted prices for similar assets in active markets or have been derived from observable market data. Accounts receivable Accounts receivable include trade receivables and notes receivable from customers. The notes are generally due within nine months . The Company receives notes receivable in exchange for accounts receivable from certain customers in China that are secured by the customer’s affiliated financial institution. An allowance for doubtful accounts is calculated based on the aging of the Company’s trade receivables, historical experience, and management judgment. The Company writes off trade receivables against the allowance when management determines a balance is uncollectible and is no longer actively pursuing collection of the receivable. Inventories Inventories consist of on-hand raw materials, work-in-progress inventories and finished goods. Raw materials and work-in-progress inventories are stored mainly on the Company’s premises. Finished goods are stored on the Company’s premises as well as on consignment at certain customer sites. Inventories are stated at the lower of standard cost, which approximates actual cost determined on the weighted average basis, or net realizable value. Inventories are recorded using the first-in, first-out method. The Company routinely evaluates quantities and values of inventories in light of current market conditions and market trends, and records a write-down for quantities in excess of demand and product obsolescence. The evaluation may take into consideration historic usage, expected demand, anticipated sales price, new product development schedules, the effect new products might have on the sale of existing products, product obsolescence, customer concentrations, product merchantability and other factors. Market conditions are subject to change and actual consumption of inventory could differ from forecasted demand. The Company also regularly reviews the cost of inventories against their estimated market value and records a lower of cost or market write-down for inventories that have a cost in excess of estimated market value, resulting in a new cost basis for the related inventories which is not reversed. Business Combinations We allocate the fair value of purchase consideration to the tangible and intangible assets acquired and liabilities assumed based on their estimated fair values as of the close of acquisition. The excess of the fair value of purchase consideration over the fair values of these identifiable assets and liabilities is recorded as goodwill. When determining the fair values of assets acquired and liabilities assumed, management makes significant estimates and assumptions through established and generally accepted valuation techniques. Fair value estimates are based on the assumptions management believes a market participant would use in pricing the asset or liability. Critical estimates in valuing certain intangible assets include, but are not limited to, future expected cash flows from customer relationships and acquired patents and developed technology as well as discount rates. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. Amounts recorded in a business combination may change during the measurement period, which is a period not to exceed one year from the date of acquisition, as additional information about conditions existing at the acquisition date becomes available. Goodwill Goodwill is reviewed for impairment annually in the fourth fiscal quarter or more frequently if events or changes in circumstances indicate that the carrying value of goodwill may not be recoverable. The Company will assess the qualitative factors to determine whether it is more likely than not that the fair value of its reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step goodwill impairment. If the Company determines that it is more likely than not that its fair value is less than its carrying amount, then the two-step goodwill impairment test is performed. The first step, identifying a potential impairment, compares the fair value of the reporting unit with its carrying amount. If the carrying amount exceeds its fair value, the second step would need to be performed; otherwise, no further steps are required. The second step, measuring the impairment loss, compares the implied fair value of the goodwill with the carrying amount of the goodwill. Any excess of the goodwill carrying amount over the implied fair value is recognized as an impairment loss, and the carrying value of goodwill is written down to fair value. The Company had no goodwill impairment in 2018 or 2017. Long-lived assets Property, plant and equipment are stated at cost, net of accumulated depreciation and amortization. Repairs and maintenance costs are expensed as incurred. Depreciation and amortization are computed using the straight-line method over the following estimated useful lives: Buildings 20-30 years Machinery and equipment 2-7 years Furniture, fixtures and office equipment 3-5 years Software 5-7 years Leasehold improvements life of the asset or lease term, if shorter Intangible assets acquired in a business combination are recorded at fair value. Identifiable finite-lived intangible assets are amortized over the period of estimated benefit using the straight-line method, reflecting the pattern of economic benefits associated with these assets. The estimated useful lives of the Company’s finite-lived intangible assets generally range from two to seven years. The acquired land use rights in China have an estimated useful life of 45 years. Assets held for sale are measured at the lower of carrying value or the fair value less cost to sell. The carrying value of intangible assets and other long-lived assets is reviewed on a regular basis for the existence of facts or circumstances, both internally and externally, that may suggest impairment. Some factors which the Company considers to be triggering events for impairment review include a significant decrease in the market value of an asset, a significant change in the extent or manner in which an asset is used, a significant adverse change in the business climate that could affect the value of an asset, an accumulation of costs for an asset in excess of the amount originally expected, a current period operating loss or cash flow decline combined with a history of operating loss or cash flow uses or a projection that demonstrates continuing losses and a current expectation that, it is more likely than not, a long-lived asset will be disposed of at a loss before the end of its estimated useful life. If one or more of such facts or circumstances exist, the Company will evaluate the carrying value of long-lived assets to determine if impairment exists by comparing it to estimated undiscounted future cash flows over the remaining useful life of the assets. If the carrying value of the assets is greater than the estimated future cash flow, the assets are written down to the estimated fair value. The Company’s cash flow estimates contain management’s best estimates, using appropriate and customary assumptions and projections at the time. Any write-down would be treated as a permanent reduction in the carrying amount of the asset and an operating loss would be recognized. The Company recorded asset impairment charges of $1.0 million and $0.4 million in restructuring charges in 2018 and 2017, respectively (see Note 11). There were no asset impairment charges in 2016. Revenue recognition See Note 3. Product warranties The Company generally provides warranties to cover defects in workmanship, materials and manufacturing for a period of one to three years to meet the stated functionality as agreed to in each sales arrangement. Products are tested against specified functionality requirements prior to delivery, but the Company nevertheless from time to time experiences claims under its warranty guarantees. The Company accrues for estimated warranty costs under those guarantees based upon historical experience, and for specific items, at the time their existence is known and the amounts are determinable. Research and development Research and development expense consists of personnel costs, including stock-based compensation expense, for the Company’s research and development personnel and product development costs, including engineering services, development software and hardware tools, depreciation of capital equipment and facility costs. Research and development costs are expensed as incurred. Advertising costs Advertising costs are expensed as incurred and, to date, have not been significant. Stock-based compensation The Company grants stock-based awards to employees, consultants and directors. The stock-based awards, including stock options, restricted stock units, employee stock purchase rights, stock appreciation units and market-based awards, are accounted for at estimated fair values. Vesting of stock-based awards is generally subject to the grantee’s continuing service to the Company. The Company generally determines the fair value of stock options and stock appreciation rights utilizing the Black-Scholes-Merton option-pricing model, or a lattice-binomial option-pricing model for stock-based awards with a market condition. The fair value of employee grants is measured on the date of grant and then recognized over the period during which an employee is required to provide services in exchange for the award, known as the requisite service period (usually the vesting period) on a straight-line basis. The fair value of non-employee grants is measured on the date of grant and then marked to market until vest dates and then recognized over the requisite service period. The Company records expense and an equal adjustment to the liability for stock appreciation units equal to the fair value of the vested portion of the awards as of each period end. Each reporting period thereafter, compensation expense will be recorded based on the remaining service period and the then fair value of the award until vesting of the award is completed. After vesting is completed, the Company will continue to re-measure the fair value of the liability each reporting period until the award is exercised or expires, with changes in the fair value of the liability recorded in the consolidated statements of operations. Restricted stock units are valued at the closing sales price as quoted on the New York Stock Exchange on the date of grant, and are converted into shares of common stock upon vesting on a one-for-one basis. The compensation expense related to the restricted stock units is determined using the fair value of common stock on the date of grant, and the expense is recognized on a straight-line basis over the vesting period. Employee stock purchase rights are accounted for at fair value, utilizing the Black-Scholes-Merton option-pricing model. Stock-based compensation expense for modified stock-based awards are recognized using the pool approach, under which the remaining compensation cost from the original awards plus the incremental costs, if any, of the related modified awards is recognized in its entirety over the remaining portion of the requisition service period of the corresponding modified awards. Stock-based compensation expense recognized at fair value includes the impact of estimated forfeitures. The Company estimates future forfeitures at the date of grant and revises the estimates, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Income taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the carrying amounts of existing assets and liabilities in the financial statements and their respective tax bases, and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities from a change in tax rates is recognized in the consolidated statement of operations in the period that includes the enactment date. The Company operates in various tax jurisdictions and is subject to audit by various tax authorities. In preparing the Company’s consolidated financial statements, the Company is required to estimate its taxes in each of the jurisdictions in which it operates. The Company estimates actual current tax exposure as well as assesses temporary differences resulting from different treatment of items, such as accruals and allowances not currently deductible for tax purposes. These differences result in deferred tax assets which represent future tax benefits to be received when certain expenses previously recognized in the financial statements become deductible expenses under applicable income tax laws, or loss credit carryforwards are utilized. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of a deferred tax asset will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. A valuation allowance is recorded for loss carryforwards and other deferred tax assets where it is more likely than not that such deferred tax assets will not be realized. The Company classifies its net deferred tax assets as other long-term assets and deferred tax liabilities as noncurrent liabilities on its consolidated balance sheet. Foreign currency Generally the functional currency of the Company’s international subsidiaries is the local currency. The Company translates the financial statements of these subsidiaries to U.S. dollars using month-end rates of exchange for assets and liabilities, and average rates of exchange for revenue, costs, and expenses. Translation gains and losses are recorded in accumulated other comprehensive income (loss) as a component of stockholders’ equity. Effective July 1, 2016, the Company has established a hedging program using monthly forward exchange contracts as economic hedges to protect against volatility of foreign exchange rate exposure of its net intercompany activities based on a cost-benefit analysis that considers that magnitude of the exposure, the volatility of the exchange rate and the cost of the hedging instruments. The forward contracts are not designated for hedge accounting and are marked to market at fair value and reported as either other current assets or accounts payable. Any changes in the fair value are recorded as foreign exchange gain (loss) and help mitigate the changes in the value of the underlying net intercompany balances. The Company recognized a $2.2 million loss and $2.1 million gain in 2018 and 2017, respectively, relating to its foreign currency contracts within other income, net. Net foreign exchange gain (loss) was $1.4 million , $(0.5) million , and $(0.1) million in 2018, 2017, and 2016, respectively. These gains and losses were recorded as other income, net in the Company’s consolidated statements of operations. The Company presents the cash flows relating to these foreign exchange contracts as investing activities in its consolidated statements of cash flows. During the six months ended December 31, 2018, the Company temporarily discontinued entering into forward exchange contracts. This may increase the risks to us arising from the short-term impact of foreign currency fluctuations. Net income (loss) per share Basic net income (loss) per share is calculated by dividing net income (loss) by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per share is calculated by dividing net income (loss) by the weighted average number of common shares and potential dilutive common share equivalents outstanding during the period if the effect is dilutive. Accounting standards update recently adopted Effective January 1, 2017, the Company adopted ASU 2016-9, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-9”). ASU 2016-9 simplifies certain aspects of the accounting for shared-based payment transactions, including income taxes, classification of awards and classification in the statement of cash flows. It eliminates the requirement to delay the recognition of excess tax benefits until current taxes payable are reduced. Upon adoption, the Company’s previously unrecognized excess tax benefits of $8.6 million had no impact on its accumulated deficit balance as the related U.S. deferred tax assets were fully offset by a valuation allowance. The Company elected to apply the change in presentation in the statements of cash flows prospectively and elected to continue to account for estimated forfeitures over the vesting period of the share-based awards. In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-9, Revenue from Contracts with Customers (“ASU 2014-9”). The standard, along with the amendments issued in 2016 and 2015, provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. ASU 2014-9 is required to be adopted, using either of two methods: (i) retrospective to each prior reporting period presented with the option to elect certain practical expedients as defined within ASU 2014-9; or (ii) retrospective with the cumulative effect of initially applying ASU 2014-9 recognized at the date of initial application and providing certain additional disclosures. This standard, as amended, is effective for annual and interim periods beginning after December 15, 2017 and permits entities to early adopt for annual and interim reporting periods beginning after December 15, 2016. The Company adopted this standard as of January 1, 2018, using the full retrospective transition method. See Note 3 for more details. In May 2017, the FASB issued ASU No. 2017-9, Compensation—Stock Compensation (718)— Scope of Modification Accounting (ASU 2017-9”). This guidance redefines which changes to the terms and conditions of a share-based payment award require an entity to apply modification accounting for a share-based payment. ASU 2017-9 is effective for interim and annual periods after December 15, 2017 and early adoption is permitted in any interim period. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In January 2017, the FASB issued ASU 2017-1, Business Combinations (Topic 805) : Clarifying the Definition of a Business (“ASU 2017-1”). This standard provides a framework in determining when a set of assets and activities is a business. ASU 2017-1 is effective for interim and annual periods beginning after December 15, 2017 on a prospective basis. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASC 2016-18”). This standard provides guidance on the classification and presentation of restricted cash in the statement of cash flows and must be applied retrospectively. ASU 2016-18 is effective for fiscal years beginning after December 15, 2017. The Company adopted this standard effective January 1, 2018. The reclassified restricted cash balances from investing activities to changes in cash, cash equivalents and restricted cash on the condensed consolidated statements of cash flows were not material for all periods presented. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). This standard provides guidance on the tax accounting for the transferring and receiving entities upon transfer of an asset. ASU 2016-16 is effective for the Company’s interim and annual periods beginning after December 15, 2017 and should be applied on a modified retrospective basis. Upon adoption of this standard on January 1, 2018, the Company recorded $1.8 million to accumulated deficit balance for intra-entity transfer of an asset other than inventory in prior years. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). This standard provides guidance on the classification of certain cash receipts and payments in the statement of cash flows. It is effective, retrospectively, for the Company’s annual and interim reporting periods beginning after December 15, 2017 or prospectively from the earliest date practicable if retrospective application is impracticable. The Company adopted this standard effective January 1, 2018, using the retrospective transition method. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In January 2016, the FASB issued ASU 2016-1, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-1”). ASU 2016-1 revises an entity’s accounting related to (1) the classification and measurement of investments in equity securities and (2) the presentation of certain fair value changes for financial liabilities measured at fair value. It also amends certain disclosure requirements associated with the fair value of financial instruments and is effective for the Company’s annual and interim reporting periods beginning after December 15, 2017. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In March 2017, the FASB issued ASU No. 2017-7, Compensation-Retirement Benefits (Topic 715)-Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (“ASU 2017-7”). This guidance revises the presentation of employer-sponsored defined benefit pension and other postretirement plans for the net periodic benefit cost in the statement of operations and requires that the service cost component of net periodic benefit be presented in the same income statement line items as other employee compensation costs for services rendered during the period. The other components of the net benefit costs are required to be presented in the statement of operations separately from the service cost component and outside the subtotal of income from operations. This guidance allows only the service cost component of net periodic benefit costs to be eligible for capitalization. ASU 2017-7 is effective for interim and annual periods after December 15, 2017. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. Recent accounting standards update not yet effective In January 2017, the FASB issued ASU 2017-4, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (“ASU 2017-4”). This standard amends the goodwill impairment test to compare the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, up to the total amount of goodwill allocated to that reporting unit. ASU 2017-4 is effective prospectively for interim and annual periods beginning after December 15, 2019. Early adoption is permitted for interim and annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company has not determined whether it will elect early adoption and is currently evaluating the impact of the adoption of this standard on its consolidated financial statements and related disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 amends existing guidance on the impairment of financial assets and adds an impairment model that is based on expected losses rather than incurred losses and requires an entity to recognize as an allowance its estimate of expected credit losses for its financial assets. An entity will apply this guidance through a cumulative-effect adjustment to retained earnings upon adoption (a modified-retrospective approach) while a prospective transition

The Company and basis of presen

The Company and basis of presentation	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and basis of presentation	The Company and basis of presentation Business and organization NeoPhotonics Corporation and its subsidiaries (NeoPhotonics or the Company) develops, manufactures and sells optoelectronic products that transmit, receive and switch high speed digital optical signals for communications networks. The Company sells its products worldwide, primarily to leading network equipment manufacturers. Certain Significant Risks and Uncertainties The Company operates in a dynamic industry and, accordingly, can be affected by a variety of factors. For example, any of the following areas could have a negative effect on the Company in terms of its future financial position, results of operations or cash flows: the general state of the U.S., China and world economies; the highly cyclical nature of the industries the Company serves; the loss of any of a small number of its larger customers; ability to obtain additional financing; inability to meet certain debt covenants; failure to successfully integrate completed acquisitions; fundamental changes in the technology underlying the Company’s products; the hiring, training and retention of key employees; successful and timely completion of product design efforts; and new product design introductions by competitors. Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. Intercompany accounts and transactions have been eliminated in consolidation. Going Concern Accounting Standards Update (“ASU”) No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern, requires an entity to disclose information about its potential inability to continue as a going concern when conditions and events indicate that it is probable that the entity may be unable to meet its obligations as they become due within one year. Management has assessed the Company’s ability to continue as a going concern within one year of the filing date of this Annual Report on Form 10-K with the Securities and Exchange Commission ("SEC") in March 2019. The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business. As of December 31, 2018, the Company’s working capital was $116.8 million , including available cash, cash equivalents, short-term investments and restricted cash of approximately $76.7 million . In 2018, the Company had operating losses of $41.7 million and cash from operations of $19.6 million . It had an accumulated deficit of approximately $397.5 million as of December 31, 2018. Through 2017 and the early part of 2018, the Company's operating results and cash flows were negatively affected by demand that was lower than customer estimates that were used to put capacity in place in 2016 and 2017. In the second half of 2018, demand continued to strengthen, primarily due to volume growth in the Americas as a result of metro and, particularly, data center interconnect deployments, as well as being the result of increased domestic provincial deployments in China plus exports by Chinese OEMs for international deployments. To adjust to the demand that was less than estimates used for capacity decisions, the Company implemented restructuring plans in May and September 2017 that included a reduction in force and consolidation of facilities, in order to reduce expenses. The Company has also reduced or delayed certain product development projects and capital expenditures, aggressively pursued collections of accounts and notes receivable and continued to closely manage production and inventory levels. The Company continues to implement actions to improve cash flow and profitability. In September 2017, the Company entered into a revolving line of credit agreement with Wells Fargo Bank, National Association ("Wells Fargo") which provides for borrowings under an accounts receivable based formula up to a maximum of $50.0 million . As of December 31, 2018, $36.0 million was outstanding under this line. The remaining borrowing capacity as of December 31, 2018 was $14.0 million , of which $5.0 million is required to be maintained as unused borrowing capacity. Borrowings under the Wells Fargo line are not due until June 30, 2022 as long as the borrowing base is not less than the outstanding amount (see Note 12). Additionally, the Company had $4.8 million of notes payable and $2.9 million of current portion of long-term debt as of December 31, 2018, which it plans to pay out of its existing available cash. The Company currently believes it will have sufficient resources to fund its currently planned operations and expenditures over the next twelve months without additional financing or other actions. In addition, the Company believes there are a number of ongoing and potential actions that may further strengthen its projected cash and projected financial position. The Company operates in an industry that makes its prospects difficult to evaluate with certainty. Future declines in China market demand or other changes to the Company’s forecasts could adversely affect the Company’s results of operations, financial position and cash flows. As a result, the Company may need to raise additional debt or equity capital to fund its operations. Any additional debt arrangements may likely require regular interest and principal payments which could adversely affect the Company’s operations. There can be no assurance that additional debt or equity capital will be available on acceptable terms, or at all.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Adoption of ASC Topic 606, “Revenue from Contracts with Customers” On January 1, 2018, the Company adopted Topic 606 using the full retrospective method which required it to restate each prior reporting period presented. The adoption did not have a material impact on the Company's consolidated financial statements and as a result, no changes were made to prior reporting periods presented. Product revenue The Company develops, manufactures and sells optoelectronic products that transmit, receive, modify and switch high speed digital optical signals for communications networks. Revenue is derived primarily from the sale of hardware products. The Company sells its products worldwide, primarily to leading network equipment manufacturers. Revenue recognition Revenue is recognized upon transfer of control of promised products or services to customers in an amount that reflects the consideration the Company expects to receive in exchange for those products or services. The Company generally bears all costs, risk of loss or damage and retains title to the goods up to the point of transfer of control of promised products to customer. Revenue related to the sale of consignment inventories at customer vendor managed locations is not recognized until the products are pulled from consignment inventories by customers. In instances where acceptance of the product or solutions is specified by the customer, revenue is deferred until such required acceptance criteria have been met. Shipping and handling costs are included in the cost of goods sold. The Company presents revenue net of sales taxes and any similar assessments. Nature of products Revenue from sale of hardware products is recognized upon transfer of control to the customer. The performance obligation for the sale of hardware products is satisfied at a point in time. The Company has aligned its products in two groups - High Speed Products and Network Products and Solutions. The following presents revenue by product group (in thousands): Years Ended December 31, 2018 2017 2016 High Speed Products $ 275,803 $ 241,780 $ 277,258 Network Products and Solutions 46,737 51,114 134,165 Total revenue $ 322,540 $ 292,894 $ 411,423 The following table presents the Company's revenue information by geographical region. Revenue is classified based on the ship to location requested by the customer. Such classification recognizes that for many customers, including those in North America or in Europe, designated shipping points are often in China or elsewhere in Asia (in thousands): Years Ended December 31, 2018 2017 2016 China $ 187,277 $ 161,637 $ 254,625 Americas 70,906 52,973 76,091 Rest of world 64,357 78,284 80,707 Total revenue $ 322,540 $ 292,894 $ 411,423 Certain prior period amounts have been reclassified to conform to the current period presentation. Deferred revenue The Company records deferred revenue when cash payments are received or due in advance of our performance. Refer to Note 9 for disclosure of deferred revenue balances. The increase in the deferred revenue balances during 2018 was immaterial, offset by approximately $0.9 million of revenue recognized during 2018 that was included in the deferred revenue balance as of December 31, 2017. The increase in the deferred revenue balances during 2017 was $1.6 million , offset by approximately $1.1 million of revenue recognized during 2017, respectively, that was included in the deferred revenue balance as of December 31, 2016. Contract assets The Company records contract assets when the revenue is recognized but the customer payment is contingent on a future event. The balance of contract assets as of December 31, 2018 and December 31, 2017 was immaterial. Refund liabilities The Company records refund liabilities when the contract permits the customer to return the product if certain circumstances arise. The balance of refund liabilities as of December 31, 2018 and December 31, 2017 was immaterial.

Cash, cash equivalents, short-t

Cash, cash equivalents, short-term investments and restricted cash	12 Months Ended
	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash, cash equivalents, short-term investments and restricted cash	Cash, cash equivalents, short-term investments and restricted cash The following table summarizes the Company’s cash, cash equivalents, short-term investments, and restricted cash at December 31, 2018 and 2017 (in thousands): December 31, 2018 December 31, 2017 Cash and cash equivalents: Cash $ 58,185 78,906 Cash equivalents — — Cash and cash equivalents $ 58,185 $ 78,906 Short-term investments $ 7,481 $ 12,311 Restricted cash $ 11,053 $ 2,658 December 31, 2018 December 31, 2017 Cash and cash equivalents $ 58,185 $ 78,906 Restricted cash 11,053 2,658 Total cash, cash equivalents and restricted cash shown in the consolidated statement of cash flows $ 69,238 $ 81,564 The following table summarizes the Company’s unrealized gains and losses related to the cash equivalents and short-term investments in marketable securities designated as available-for-sale (in thousands): As of December 31, 2018 As of December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Marketable securities: Money market accounts $ — $ — $ — $ — $ — $ — $ — $ — Money market funds 7,481 — — 7,481 11,561 — — 11,561 Corporate debt securities — — — — — — — — U.S. government securities — — — — 751 — (1 ) 750 Sovereign government bonds — — — — — — — — Total $ 7,481 $ — $ — $ 7,481 $ 12,312 $ — $ (1 ) $ 12,311 Reported as: Cash equivalents $ — $ — $ — $ — $ — $ — $ — $ — Short-term investments 7,481 — — 7,481 12,312 — (1 ) 12,311 Total $ 7,481 $ — $ — $ 7,481 $ 12,312 $ — $ (1 ) $ 12,311 As of December 31, 2018 and 2017, maturities of marketable securities were as follows (in thousands): December 31, 2018 December 31, 2017 Less than 1 year $ 7,481 $ 12,311 Due in 1 to 2 years — — Due in 3 to 5 years — — Total $ 7,481 $ 12,311 Realized gains and losses on the sale of marketable securities during the years ended December 31, 2018, 2017 and 2016 were immaterial. The Company did not recognize any impairment losses on its marketable securities during the years ended December 31, 2018, 2017 or 2016. As of December 31, 2018, the Company did not have any investments in marketable securities that were in an unrealized loss position for a period in excess of 12 months.

Fair value measurements

Fair value measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair value measurements	Fair value measurements Assets and Liabilities Measured at Fair Value on a Recurring Basis The following table presents the Company’s assets that are measured at fair value on a recurring basis (in thousands): December 31, 2018 December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash equivalents and short-term investments: Money market funds $ 7,481 $ — $ — $ 7,481 $ 11,561 $ — $ — $ 11,561 U.S. government securities — — — — 750 — — 750 Money market accounts — — — — — — — — Total $ 7,481 $ — $ — $ 7,481 $ 12,311 $ — $ — $ 12,311 Mutual funds held in Rabbi Trust, recorded in other long-term assets $ 465 $ — $ — $ 465 $ 523 $ — $ — $ 523 The Company offers a Non-Qualified Deferred Compensation Plan (“NQDC Plan”) to a select group of its highly compensated employees to provide participants the opportunity to defer payment of certain compensation as defined in the NQDC Plan. A Rabbi Trust has been established to fund the NQDC Plan obligation, which was fully funded as of December 31, 2018 and 2017. The assets held by the Rabbi Trust are in the form of exchange traded mutual funds and are included in the Company’s other long-term assets on its consolidated balance sheets as of December 31, 2018 and 2017. Level 1 assets are determined by using quoted prices in active markets for identical assets. The fair values of Level 2 assets are priced based on quoted market prices for similar instruments or non-binding market prices that are corroborated by observable market data using inputs such as benchmark yields, broker quotes and other similar data. The following table presents the Company’s liabilities that are measured at fair value on a recurring basis (in thousands): As of December 31, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Rusnano payment derivative $ — $ — $ 2,000 $ 2,000 $ — $ — $ 389 $ 389 Foreign currency forward contracts — — — — — (43 ) — (43 ) $ — $ — $ 2,000 $ 2,000 $ — $ (43 ) $ 389 $ 346 The fair value of the Rusnano payment derivative is based on the Company’s estimate (see Note 14). The fair values of the foreign currency forward contracts are based on quoted market rates and market observable data for similar instruments. There were no transfers between levels of the fair value hierarchy during the periods presented. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis In 2018, the Company wrote-off $1.0 million of property, plant and equipment within operating expenses. These assets were measured at fair value which is zero due to events or circumstances the Company identified as having significant impact on their fair value during 2018. In 2018, the Company reclassified $2.5 million of property, plant and equipment within assets held for sale. The estimated fair value less direct costs of sale approximates the related carrying value of these assets as of December 31, 2018 (see Note 9). There were no other assets or liabilities measured at fair value on a nonrecurring basis in 2018 and 2017. Assets and Liabilities Not Measured at Fair Value The carrying values of cash, restricted cash, accounts receivable, accounts payable, notes payable and short-term borrowing approximate their fair values due to the short-term nature and liquidity of these financial instruments. The fair value of the Company’s long-term debt have been calculated using an estimate of the interest rate the Company would have had to pay on the issuance of liabilities with a similar maturity and discounting the cash flows at that rate which it considers to be a level 2 fair value measurement and was not materially different than the carrying value as of December 31, 2018 and 2017 as the interest rates approximated rates currently available to the Company. The fair values do not necessarily give an indication of the amount that the Company would currently have to pay to extinguish any of this debt.

Net loss per share

Net loss per share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Net loss per share	Net loss per share The following table sets forth the computation of the basic and diluted net loss per share attributable to NeoPhotonics Corporation common stockholders for the periods indicated (in thousands, except per share amounts): Years Ended December 31, 2018 2017 2016 Numerator: Net loss $ (43,637 ) $ (53,333 ) $ (205 ) Denominator: Weighted average shares used to compute per share amount: Basic 45,144 43,431 41,798 Dilutive effect of equity awards — — — Diluted 45,144 43,431 41,798 Basic net loss per share $ (0.97 ) $ (1.23 ) (0.00) Diluted net loss per share $ (0.97 ) $ (1.23 ) (0.00) The Company has excluded the impact of the following outstanding employee stock options, restricted stock units, common stock warrants and shares expected to be issued under its employee stock purchase plan from the computation of diluted net loss per share, as their effect would have been antidilutive (in thousands): December 31, 2018 2017 2016 Employee stock options 3,203 3,934 4,301 Restricted stock units 2,486 2,405 2,089 Market-based restricted stock units 695 — — Employee stock purchase plan 414 421 306 6,798 6,760 6,696

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Business Combinations	Business Combinations EMCORE Corporation On January 2, 2015, the Company closed an acquisition of certain assets and assumed certain liabilities of the tunable laser product lines of EMCORE Corporation (“EMCORE”) for an original purchase price of $17.5 million , pursuant to the terms of the Asset Purchase Agreement between the parties dated October 22, 2014. Consideration for the transaction consisted of $1.5 million in cash and a promissory note (the “EMCORE Note”) of approximately $16.0 million , which was subsequently adjusted to $15.5 million in connection with a True-Up Confirmation Agreement (the “True-Up Agreement”) executed by and between the Company and EMCORE on April 16, 2015. The final adjusted purchase price for the acquisition was approximately $17.0 million . The Company accounted for this acquisition as a business combination. With the acquisition of the EMCORE ultra narrow linewidth tunable laser products, the Company aims to strengthen its portfolio of High Speed Products. In connection with the acquisition, the Company incurred approximately $0.9 million in total acquisition-related costs related to legal, accounting and other professional services. The acquisition costs were expensed as incurred and included in operating expenses in the Company’s consolidated statement of operations. The fair values assigned to intangible assets acquired were based on valuations using estimates and assumptions provided by management, with the assistance of an independent third party appraisal firm. The excess purchase price over those fair values was recorded as goodwill. The Company used best estimates and assumptions as part of the purchase price allocation process to value assets acquired and liabilities assumed at the acquisition date and during the Company’s process of obtaining further information, further refined estimates and assumptions, including the acquired property, plant and equipment, prepaid and other current assets, which primarily consisted of held-for-sale assets and accounts payable. As a result, during the measurement period completed in 2015, the Company recorded adjustments related to the acquired net accounts receivable, the acquired net inventories, the assumed sales tax accrual and the acquired prepaid expenses and other current assets by immaterial amounts, and decreased goodwill by a corresponding net amount. Goodwill recorded consisted of a valuable assembled workforce and market synergy. The amounts assigned to goodwill are deductible for income tax purposes. The following table summarizes the allocation of the assets acquired and liabilities assumed as of the acquisition date and subsequent adjustments (in thousands): Total purchase consideration: Cash paid $ 1,500 Notes payable 15,482 Total $ 16,982 Fair value of assets acquired: Accounts receivable $ 9,274 Inventories 1,693 Prepaid expenses and other current assets 670 Property, plant and equipment 6,917 Intangible assets acquired: Developed technology 4,100 Customer relationships 700 Total $ 23,354 Less: fair value of liabilities assumed: Accounts payable $ (7,427 ) Accrued liabilities (60 ) Total $ (7,487 ) Goodwill $ 1,115 Purchased intangibles with finite lives will be amortized on a straight-line basis over their respective estimated useful lives. The following table presents details of the purchase price allocated to the acquired intangible assets at the acquisition date: Useful Life Purchased intangible assets (In years) (In thousands) Developed technology 7 $ 4,100 Customer relationships 2 700 Total purchased intangible assets $ 4,800 EigenLight Corporation In November 2015 the Company closed an acquisition of the business and products of EigenLight Corporation for cash consideration of $0.4 million in an asset transaction. The Company accounted for this as a business combination and the majority of the purchase price was allocated to inventory and property, plant and equipment.

Purchased intangible assets

Purchased intangible assets	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Purchased intangible assets	Purchased intangible assets Purchased intangible assets consist of the following (in thousands): December 31, 2018 December 31, 2017 Gross Assets Accumulated Amortization Net Assets Gross Assets Accumulated Amortization Net Assets Technology and patents $ 37,029 $ (34,995 ) $ 2,034 $ 37,684 $ (34,923 ) $ 2,761 Customer relationships 15,146 (15,026 ) 120 15,425 (14,835 ) 590 Leasehold interest 1,238 (374 ) 864 1,309 (366 ) 943 $ 53,413 $ (50,395 ) $ 3,018 $ 54,418 $ (50,124 ) $ 4,294 Amortization expense relating to technology and patents and the leasehold interest intangible assets is included within cost of goods sold, and customer relationships and the non-compete agreements within operating expenses. The following table presents details of the amortization expense of the Company’s purchased intangible assets as reported in the consolidated statements of operations (in thousands): Years ended December 31, 2018 2017 2016 Cost of goods sold $ 756 $ 869 $ 2,871 Operating expenses 475 472 1,609 Total $ 1,231 $ 1,341 $ 4,480 The estimated future amortization expense of purchased intangible assets as of December 31, 2018, is as follows (in thousands): 2019 $ 856 2020 737 2021 644 2022 28 2023 28 Thereafter 725 $ 3,018

Balance sheet components

Balance sheet components	12 Months Ended
	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Balance sheet components	Balance sheet components Restricted Cash Restricted cash was as follows (in thousands): December 31, 2018 2017 Restricted in connection with notes payable and short-term borrowing (see Note 12) $ 2,589 $ 537 Restricted in connection with asset purchase agreement (see Note 10) 2,019 2,121 Restricted in connection with a current legal dispute with APAT OE (See Note 10) 5,156 — Restricted in connection with government grants received in advance 1,289 — Total restricted cash $ 11,053 $ 2,658 Reported as: Restricted cash $ 11,053 $ 2,658 Accounts receivable, net Accounts receivable, net were as follows (in thousands): December 31, 2018 2017 Accounts receivable $ 74,343 $ 65,499 Trade notes receivable 672 2,356 Allowance for doubtful accounts (264 ) (626 ) $ 74,751 $ 67,229 The table below summarizes the movement in the Company’s allowance for doubtful accounts (in thousands): Balance at December 31, 2015 $ (843 ) Reversal of provision for bad debt 382 Write-offs, net of recoveries 36 Balance at December 31, 2016 (425 ) Provision for bad debt (577 ) Write-offs, net of recoveries 376 Balance at December 31, 2017 (626 ) Reversal of provision for bad debt 428 Write-offs, net of recoveries (66 ) Balance at December 31, 2018 $ (264 ) Inventories Inventories were as follows (in thousands): December 31, 2018 2017 Raw materials $ 27,806 $ 33,400 Work in process 13,044 13,246 Finished goods (1) 11,309 20,655 $ 52,159 $ 67,301 (1) Included in finished goods was $5.6 million and $7.1 million of inventory at customer vendor managed inventory locations at December 31, 2018 and 2017 , respectively. Assets held for sale In December 2018, the Company entered into an agreement with Joint Stock Company Rusnano, a related party, for Joint Stock Company Rusnano group to purchase the 100% interest in the operations of NeoPhotonics Corporation, LLC, the Company's manufacturing operations in Russia. In 2018, the Company recorded additional restructuring expense of $1.6 million for the Rusnano payment derivative related to these operations. As of December 31, 2018, the Company reclassified assets with carrying value of $3.0 million as held for sale primarily consisting of $2.5 million of property, plant and equipment and $0.5 million of prepaid expenses and other current assets. The estimated fair value less direct costs of sale approximates the related carrying value. The balance for liabilities held for sale as of December 31, 2018 was immaterial and was primarily included in accrued and other current liabilities. Prepaid expenses and other current assets Prepaid expenses and other current assets were as follows (in thousands): December 31, 2018 2017 Prepaid taxes and taxes receivable $ 5,461 $ 15,162 Transition services agreement receivable (see Note 10) 11,999 12,817 Deposits and other prepaid expenses 3,020 4,138 Other receivable 6,125 4,118 $ 26,605 $ 36,235 Property, plant and equipment, net Property, plant and equipment, net were as follows (in thousands): December 31, 2018 2017 Land $ 3,157 $ 3,083 Buildings 23,379 24,102 Machinery and equipment 187,746 189,527 Furniture, fixtures, software and office equipment 10,201 9,948 Leasehold improvements 22,000 26,007 246,483 252,667 Less: Accumulated depreciation (146,393 ) (125,102 ) $ 100,090 $ 127,565 Depreciation expense was $29.9 million , $27.0 million and $17.9 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. In 2017, the Company wrote off certain leasehold improvements in its facilities in California and recorded a restructuring charge of $0.1 million in connection with the Company’s restructuring actions. Purchases of property, plant and equipment unpaid as of December 31, 2018, 2017 and 2016 was $1.5 million , $10.0 million and $16.1 million , respectively. Accrued and other current liabilities Accrued and other current liabilities were as follows (in thousands): December 31, 2018 2017 Employee-related $ 14,899 $ 12,990 Transition services agreement payables (see Note 10) 11,769 11,222 Asset sale related contingent liabilities (see Note 10) 6,751 7,135 Income and other taxes payable 1,580 542 Deferred revenue, current 1,114 939 Accrued warranty 672 1,334 Rusnano payment derivative 2,000 — Accrued litigation settlement 2,645 — Other accrued expenses 8,858 9,080 $ 50,288 $ 43,242 Accrued warranty The table below summarizes the movement in the warranty accrual, which is included in accrued and other current liabilities (in thousands): Years ended December 31, 2018 2017 2016 Beginning balance $ 1,334 $ 678 $ 1,175 Warranty accruals 399 1,263 102 Settlements (1,061 ) (607 ) (599 ) Ending balance $ 672 $ 1,334 $ 678 Other noncurrent liabilities Other noncurrent liabilities were as follows (in thousands): December 31, 2018 2017 Pension and other employee-related $ 4,529 $ 4,675 Deferred rent 3,058 2,908 Deferred revenue — 617 Government grant 2,108 1,095 Rusnano payment derivative — 389 Deferred income tax liabilities — 106 Capital lease obligation 282 — Asset retirement obligations and other 3,522 4,285 $ 13,499 $ 14,075

Asset sale

Asset sale	12 Months Ended
	Dec. 31, 2018
Discontinued Operations and Disposal Groups [Abstract]
Asset sale	Asset sale In January 2017, the Company completed the sale of its Low Speed Transceiver Products’ assets to APAT OE pursuant to an asset purchase agreement dated December 14, 2016 for consideration of approximately $25.0 million (in RMB equivalent) plus approximately $1.4 million (in RMB equivalent) post-closing transaction service fees to be received under a transition services agreement with APAT OE in which the Company will provide short-term manufacturing and other specific services pursuant to such agreement. The related supply chain purchase commitments and value-added tax obligations have been assumed by APAT OE. The receivable and payable balances related to the transition service arrangement were $12.0 million and $11.8 million , respectively, as of December 31, 2018. As of December 31, 2016, the balance in assets held for sale was $13.9 million , consisting of $13.1 million in inventories and $0.8 million in property, plant and equipment. As a result of post-closing adjustments, total consideration was reduced by approximately $3.4 million for inventory. In addition, an immaterial amount of property, plant and equipment was reclassified from assets held for sale. Upon closing, assets sold to APAT OE were approximately $12.8 million , including approximately $12.1 million in inventories and $0.7 million in property, plant and equipment. The adjusted consideration received of approximately $21.6 million is subject to further reduction of up to $10.0 million for any indemnification claims. As of December 31, 2018, the Company has a reserve of $6.8 million within accrued and other current liabilities for warranty claims. The indemnification warranties expired on June 30, 2017. The Company recognized a $2.2 million gain on the sale of these assets within operating loss in 2017. All of the Low Speed Transceiver Products were part of the Company’s Network Products and Solution product group and included the low speed optical network (PON) products for which the end-of-life plan was announced in mid-2016.

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2018
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring In 2017, the Company initiated restructuring actions in order to focus on key growth initiatives and a lower break even revenue level through lower operating expenses and manufacturing costs. Actions included a reduction in force, facilities consolidation and certain asset-related adjustments. The Company recorded $0.2 million and $3.1 million in restructuring charges within cost of goods sold and operating expenses in 2018, respectively. The Company recorded $0.8 million and $3.9 million in restructuring charges within cost of goods sold and operating expenses in 2017, respectively. Additionally, the Company recorded a charge of $2.0 million to cost of goods sold in 2017 for discontinued product inventory write-downs related the Company's decisions to end-of-life certain products. Employee Severance Facilities Consolidation Asset-Related Others Total Restructuring obligations December 31, 2017 $ — $ 1,580 $ 43 $ — $ 1,623 Charges 637 29 1,021 1,616 3,303 Cash payments (196 ) (840 ) (6 ) (5 ) (1,047 ) Non-cash settlements and other (5 ) — (1,058 ) — (1,063 ) Restructuring obligations December 31, 2018 $ 436 $ 769 $ — $ 1,611 $ 2,816

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt The table below summarizes the carrying amount and weighted average interest rate of the Company’s debt (in thousands, except percentages): December 31, 2018 December 31, 2017 Carrying Amount Interest Rate Carrying Amount Interest Rate Note payable to Shanghai Pudong Development Bank $ — — % $ 17,000 4.10 % Note payable to China CITIC Bank — — % 17,000 4.00 % Notes payable to suppliers 4,795 1,607 Total notes payable and short-term borrowing $ 4,795 $ 35,607 Long-term debt, current and non-current: Borrowing under Wells Fargo Credit Facility $ 35,961 4.41 % $ 30,018 3.29 % Mitsubishi Bank loans 11,094 1.05%-1.45% 16,924 1.05% -1.45% Mitsubishi Bank and Yamanashi Chou Bank loan 6,898 1.10 % — Unaccreted discount and issuance costs within current portion of long-term debt (161 ) (86 ) Unaccreted discount and issuance costs within long-term debt, net of current portion (441 ) (295 ) Total long-term debt, net of unaccreted discount and issuance costs $ 53,351 $ 46,561 Reported as: Current portion of long-term debt $ 2,897 $ 6,005 Long-term debt, net of current portion 50,454 40,556 Total long-term debt, net of unaccreted discount and issuance costs $ 53,351 $ 46,561 Notes payable and short-term borrowing The Company regularly issues notes payable to its suppliers in China. These notes are supported by non-interest bearing bank acceptance drafts issued under the Company’s existing line of credit facilities and are due three to six months after issuance. As a condition of the notes payable arrangements, the Company is required to keep a compensating balance at the issuing banks that is a percentage of the total notes payable balance until the amounts are settled. As of December 31, 2018, the Company’s subsidiary in China had two line of credit facilities with banking institutions: • Under the first line of credit facility with Shanghai Pudong Development Bank, the Company can borrow up to RMB 120.0 million ( $17.4 million ) for short-term loans at varying interest rates, or up to approximately RMB 240.0 million ( $34.9 million ) for bank acceptance drafts (with up to 50% compensating balance requirement). This line of credit facility expires in November 2021. In November 2017, the Company borrowed $17.0 million under this line which bears interest at 4.1% , which was repaid in May 2018. • Under the second line of credit facility with Shanghai Pudong Development Bank, which expires in November 2021 , the Company can borrow up to RMB 30.0 million ( $4.4 million ) for short-term loans at varying interest rates, or up to approximately RMB 60.0 million ( $8.7 million ) for bank acceptance drafts (with up to 50% compensating balance requirement). In December 2017, the Company's subsidiary in China entered into a third line of credit facility with China CITIC Bank in China, which expired in November 2018. The purpose of the credit facility was to provide short-term borrowings, bank acceptance drafts and letters of credits. Under this credit facility, the Company could borrow up to approximately RMB 250 million ( $36.4 million ) at varying interest rates, or up to approximately RMB 390.6 million ( $56.8 million ) for bank acceptance drafts (with up to 36% compensating balance requirement). In February 2018, the Company borrowed $17.0 million under this line which bore interest at 4.7% . The amount of $17.0 million under this line was repaid in August 2018. The Company had a line of credit facility previously with China CITIC Bank in China which expired during September 2017. In July 2017, the Company borrowed $17.0 million under this line which bore interest at LIBOR plus 2.55% . The amount of $17.0 million under this line was repaid to CITIC Bank in January 2018. Under these line of credit facilities, the non-interest bearing bank acceptance drafts issued in connection with the Company's notes payable to its suppliers in China, had an outstanding balance of $4.8 million and $1.6 million as of December 31, 2018 and December 31, 2017, respectively. In addition to the outstanding notes payable, three letters of credit totaling $1.6 million were issued to its suppliers in 2016 for equipment purchases delivered by December 2016. These letters of credit required a 30% compensating balance. As of December 31, 2016, the outstanding balance of these letters of credit was immaterial and was fully repaid as of December 31, 2018. As of December 31, 2018 and December 31, 2017, compensating balances relating to bank acceptance drafts and letters of credit issued to suppliers and the Company's subsidiaries totaled $2.6 million and $0.5 million , respectively. Compensating balances are classified as restricted cash on the Company’s consolidated balance sheets. In China, when there is a case pending in judicial court, banks may choose to limit borrowing against existing credit lines, regardless of the legitimacy of the case. The Company has a dispute pending with APAT OE in judicial court (See Note 14). The Company does not expect to make any additional draws against its credit facilities in China until this matter is resolved. Credit Facilities The Company had a credit agreement, as amended with the Comerica Bank as lead bank in the U.S. (the “Comerica Bank Credit Facility”) with a borrowing capacity of up to $30.0 million . In January 2017, the Company amended the Comerica Bank Credit Facility to extend the maturity to April 30, 2017 and to remove the covenant related to EBDITA. In April 2017, the Company amended the Comerica Bank Credit Facility to extend the maturity date to July 31, 2017 and to add a financial covenant that required maintenance of a modified EBITDA. In June 2017, the Company amended the Comerica Bank Credit Facility to extend the maturity to August 31, 2017, to allow NeoPhotonics China to borrow up to $17.0 million , to limit the indebtedness under the facility to $20.0 million and to modify the EBITDA requirement. In August 2017, the Credit Facility was further amended to extend the maturity to September 30, 2017. Borrowings under the Comerica Bank Credit Facility bore interest at an interest rate option of a base rate as defined in the agreement plus 1.75% or LIBOR plus 2.75% . The base rate was the greater of (a) the effective prime rate, (b) the Federal Funds effective rate plus one percent, and (c) the daily adjusting LIBOR rate plus one percent. In September 2017, the Company entered into a revolving line of credit agreement with Wells Fargo as the administrative agent for a lender group (the "Wells Fargo Credit Facility" or "Credit Facility"), and the amount outstanding under the Comerica Bank Credit Facility was paid in full. The Wells Fargo Credit Facility provides for borrowings equal to the lower of (a) a maximum revolver amount of $50.0 million , or (b) an amount equal to 80% - 85% of eligible accounts receivable plus 100% of qualified cash balances up to $15.0 million , less certain discretionary adjustments ("Borrowing Base"). The maximum revolver amount may be increased by up to $25.0 million , subject to certain conditions. At closing, $50.0 million was available, of which $30.0 million was drawn. The Company used $20.0 million of this amount to pay the principal and interest due under the Comerica Bank Credit Facility, which has since been terminated. The Credit Facility matures on June 30, 2022 and borrowings bear interest at an interest rate option of either (a) the LIBOR rate, plus an applicable margin ranging from 1.50% to 1.75% per annum, or (b) the prime lending rate, plus an applicable margin ranging from 0.50% to 0.75% per annum. The Company is also required to pay a commitment fee equal to 0.25% of the unused portion of the Credit Facility. The Credit Facility agreement ("Agreement") requires prepayment of the borrowings to the extent the outstanding balance is greater than the lesser of (a) the most recently calculated Borrowing Base, or (b) the maximum revolver amount. The Company is required to maintain a combination of certain defined cash balances and unused borrowing capacity under the Credit Facility of at least $20.0 million , of which at least $5.0 million shall include unused borrowing capacity. The Agreement also restricts the Company's ability to dispose of assets, permit change in control, merge or consolidate, make acquisitions, incur indebtedness, grant liens, make investments and make certain restricted payments. Borrowings under the Credit Facility are collateralized by substantially all of the Company's assets. The Company was in compliance with the covenants of this Credit Facility as of December 31, 2018. As of December 31, 2018, the outstanding balance under the Credit Facility was $36.0 million and the weighted average rate under the LIBOR option was 4.41% . The remaining borrowing capacity as of December 31, 2018 was $14.0 million , of which $5.0 million is required to be maintained as unused borrowing capacity. The Company repaid $5.0 million in January 2019, which was borrowed in December 2018. Mitsubishi Bank Loans On February 25, 2015, the Company entered into certain loan agreements and related agreements with MUFG Bank, Ltd. (the "Mitsubishi Bank") that provided for (i) a term loan in the aggregate principal amount of 500 million Japanese Yen (the “JPY”) ( $4.4 million ) (the “Term Loan A”) and (ii) a term loan in the aggregate principal amount of one billion JPY ( $9.1 million ) (the “Term Loan B” and together with the Term Loan A, the “2015 Mitsubishi Bank Loans”). The Mitsubishi Bank Loans are secured by a mortgage on certain real property and buildings owned by our Japanese subsidiary. Interest on the 2015 Mitsubishi Bank Loans accrues and is paid monthly based upon the annual rate of the monthly Tokyo Interbank Offer Rate (TIBOR) plus 1.40% . The Term Loan A requires interest only payments until the maturity date of February 23, 2018 , with a lump sum payment of the aggregate principal amount on the maturity date. The Term Loan B requires equal monthly payments of principal equal to 8,333,000 JPY until the maturity date of February 25, 2025, with a lump sum payment of the balance of 8,373,000 JPY on the maturity date. Interest on the Term Loan B is accrued based upon monthly TIBOR plus 1.40% and is secured by real estate collateral. In conjunction with the execution of the Bank Loans, the Company paid a loan structuring fee, including consumption tax, of 40,500,000 JPY ( $0.4 million ). The Term Loan A of 500 million JPY (approximately $4.4 million ) was repaid to the Mitsubishi Bank in January 2018. The 2015 Mitsubishi Bank Loans contain customary representations and warranties and customary affirmative and negative covenants applicable to the Company’s Japanese subsidiary, including, among other things, restrictions on cessation in business, management, mergers or acquisitions. The 2015 Mitsubishi Bank Loans contain financial covenants relating to minimum net assets, maximum ordinary loss and a dividends covenant. Outstanding principal balance for Term Loan B and unamortized debt issuance costs were approximately 616.8 million JPY (approximately $5.6 million ) and 66.2 million JPY (approximately $0.6 million ), respectively, as of December 31, 2018. The Company was in compliance with the related covenants as of December 31, 2018 and December 31, 2017. In March 2017, the Company entered into a loan agreement and related agreements with the Mitsubishi Bank for a term loan of 690 million JPY (approximately $6.3 million ) (the “2017 Mitsubishi Bank Loan”) to acquire manufacturing equipment for its Japanese subsidiary. This loan is secured by the manufacturing equipment owned by the Company's subsidiary in Japan. Interest on the 2017 Mitsubishi Bank Loan is based on the annual rate of the monthly TIBOR rate plus 1.00% . The 2017 Mitsubishi Bank Loan matures on March 29, 2024 and requires monthly interest and principal payments over 72 months commencing in April 2018. The loan contains customary covenants relating to minimum net assets, maximum ordinary loss and a dividends covenant. The Company was in compliance with these covenants as of December 31, 2018. The loan was available from March 31, 2017 to March 30, 2018 and 690 million JPY (approximately $6.3 million ) under this loan was fully drawn in March 2017. Mitsubishi Bank and Yamanashi Chou Bank loan In January 2018, the Company entered into a term loan agreement with Mitsubishi Bank and The Yamanashi Chou Bank, Ltd. for a term loan in the aggregate principal amount of 850 million JPY (approximately $7.7 million ) (the “Term Loan C”). The purpose of the Term Loan C is to obtain machinery for the core parts of the manufacturing line and payments for related expenses by the Company's subsidiary in Japan. The Term Loan C was available from January 29, 2018 to January 29, 2025. The full amount of the Term Loan C was drawn in January 2018. Interest on the Term Loan C is based upon the annual rate of the three months TIBOR rate plus 1.00% . The Term Loan C requires quarterly interest payments, along with the principal payments, over 82 months commencing in April 2018. The Term Loan C loan agreement contains customary representations and warranties and customary affirmative and negative covenants applicable to the Japanese Subsidiary, including, among other things, restrictions on cessation in business, management, mergers or acquisitions. The Term Loan C loan agreement contains financial covenants relating to minimum net assets and maximum ordinary loss. The Company was in compliance with these covenants as of December 31, 2018. At December 31, 2018, maturities of long-term debt were as follows (in thousands): 2019 $ 3,058 2020 3,058 2021 3,058 2022 39,019 2023 3,058 Thereafter 2,702 $ 53,953

Pension Plans

Pension Plans	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Pension Plans	Pension Plans Japan defined benefit pension plans In connection with its acquisition of NeoPhotonics Semiconductor in 2013, the Company assumed responsibility for two defined benefit plans that provide retirement benefits to its NeoPhotonics Semiconductor employees in Japan: the Retirement Allowance Plan (“RAP”) and the Defined Benefit Corporate Pension Plan (“DBCPP”). The RAP is an unfunded plan administered by the Company. Effective February 28, 2014, the DBCPP was converted to a defined contribution plan (“DCP”). In May 2014, LAPIS transferred approximately $2.0 million into the newly formed DCP which was the allowable amount that can be transferred according to the Japanese regulations. LAPIS also paid the Company approximately $0.3 million in connection with the conversion of the plan. Additionally, the Company transferred the net unfunded projected benefit obligation amount from the DBCPP to the RAP and froze the RAP benefit at the February 28, 2014 amount. Under the RAP, lump sum benefits are provided upon retirement or upon certain instances of termination. In 2014, the Company reclassified $0.2 million and $0.1 million from accumulated other comprehensive income to cost of goods sold and operating expenses, respectively. The funded status of these plans for the years ended December 31, 2018, 2017 and 2016 was as follows (in thousands): 2018 2017 2016 RAP RAP RAP Change in projected benefit obligation: Projected benefit obligation, beginning of period $ 4,616 $ 4,802 $ 5,086 Service cost — — — Interest cost 4 5 11 Benefits paid (517 ) (411 ) (551 ) Actuarial (gain)/loss 95 32 72 Curtailment/Settlement — — — Transfer from DBCPP to RAP — — — Currency translation adjustment 110 188 184 Projected benefit obligation, end of period $ 4,308 $ 4,616 $ 4,802 Change in plan assets: Plan assets at fair value, beginning of period $ — $ — $ — Employer contributions — — — Benefits paid — — — Transfer to DCP — — — Currency translation adjustment — — — Plan assets at calculated amount, end of period $ — $ — $ — Amounts recognized in consolidated balance sheets: Accrued and other current liabilities $ 257 $ 488 $ 393 Other noncurrent liabilities $ 4,051 $ 4,128 $ 4,409 Amount recognized in accumulated other comprehensive loss: Defined benefit pension plans adjustment $ 373 $ 271 $ 230 Accumulated benefit obligation, end of period $ 4,308 $ 4,616 $ 4,802 Net periodic pension cost associated with these plans for the years ended December 31, 2018, 2017 and 2016 included the following components (in thousands): 2018 2017 2016 RAP RAP RAP Service cost $ — $ — $ — Interest cost 4 5 11 Other — — — Curtailment/settlement (gain) loss — — — Net periodic pension costs $ 4 $ 5 $ 11 The projected and accumulated benefit obligations for the RAP were calculated as of December 31, 2018 and 2017 using a discount rate assumption of 0.1% and 0.1% , respectively. Estimated future benefit payments under the RAP are as follows (in thousands): 2019 $ 188 2020 513 2021 626 2022 295 2023 — 2024 - 2026 1,631 Thereafter 1,055 $ 4,308 401(k) Plan The Company maintains a savings and retirement plan qualified under Section 401(k) of the Internal Revenue Code of 1986, as amended (the "IRC"). The Company currently matches a portion of all eligible employee contributions which vest immediately. The Company’s matching contributions to the plan totaled $0.4 million , $0.5 million and $0.4 million , respectively, for the years ended December 31, 2018, 2017, and 2016.

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies Leases The Company leases various facilities under non-cancelable operating leases expiring through 2027. On June 13, 2017, the Company entered into an office lease for approximately 39,000 square feet for the Company’s current headquarters in San Jose (the “Lease”) with a commencement date of June 1, 2017. The Company’s existing office lease for the facility was terminated and replaced by the new Lease. Upon commencement, the Lease had an initial term of one hundred and twenty-three ( 123 ) months, ending September 30, 2027, (the “Initial Term”) with a monthly rental rate of $41,388 , escalating annually to a maximum monthly rental rate of approximately $72,525 in the last year of the Initial Term. Upon termination of the Lease, the Company anticipates a restoration cost of approximately $0.7 million . In September 2016, the Company entered into an office lease for approximately 64,000 square feet of office and laboratory space located adjacent to the Company’s current headquarters in San Jose (the “Lease”). The term of the Lease commenced on January 1, 2017. Upon commencement, the Lease has an initial term of one hundred and twenty-nine ( 129 ) months, ending on September 30, 2027 (the “Initial Term”), with a monthly rental rate of $144,000 , escalating annually to a maximum monthly rental rate of approximately $194,000 in the last year of the Initial Term. The Landlord has agreed to provide the office and laboratory space to the Company free of charge for the first nine months of the Initial Term through September 30, 2017. Upon termination of the Lease, the Company anticipates a restoration cost of approximately $3.1 million . As of December 31, 2018, the future minimum commitments under the Company’s non-cancelable operating leases are as follows (in thousands): Years ending December 31, 2019 $ 3,618 2020 3,113 2021 3,059 2022 3,056 2023 3,049 Thereafter 11,437 $ 27,332 The total minimum lease commitment amount above does not include minimum sublease rent income of $1.3 million receivable in the future under non-cancelable sublease agreements. The Company recognizes rent expense on a straight-line basis over the lease period. Rent expense under the Company’s operating leases was $4.2 million , $4.6 million and $2.4 million , respectively, in the years ended December 31, 2018, 2017, and 2016. Litigation From time to time, the Company is subject to various claims and legal proceedings, either asserted or unasserted, that arise in the ordinary course of business. The Company accrues for legal contingencies if the Company can estimate the potential liability and if the Company believes it is probable that the case will be ruled against it. If a legal claim for which the Company did not accrue is resolved against it, the Company would record the expense in the period in which the ruling was made. The Company believes that the likelihood of an ultimate amount of liability, if any, for any pending claims of any type (alone or combined) that will materially affect the Company’s financial position, results of operations or cash flows is remote. The ultimate outcome of any litigation is uncertain, however, and unfavorable outcomes could have a material negative impact on the Company’s financial condition and operating results. Regardless of outcome, litigation can have an adverse impact on the Company because of defense costs, negative publicity, diversion of management resources and other factors. In January 2010, Finisar Corporation, or Finisar, filed a complaint in the U.S. District Court for the Northern District of California, or the Court, against Source Photonics, Inc., MRV Communications, Inc., Oplink Communications, Inc. and the Company, or collectively, the co-defendants. In the complaint Finisar alleged infringement of certain of its U.S. patents. In 2010 the Company filed an answer to the complaint and counterclaims, asserting two claims of patent infringement and additional claims. The court dismissed without prejudice all co-defendants (including the Company) except Source Photonics, Inc., on grounds that such claims should have been asserted in four separate lawsuits, one against each defendant. This dismissal does not prevent Finisar from bringing a new similar lawsuit against the Company. In 2011 the Company and Finisar agreed to suspend their respective claims and in 2012 the Company and Finisar further agreed to toll their respective claims. While there has been no action on this matter since 2012, the Company is currently unable to predict the outcome of this dispute and therefore cannot determine the likelihood of loss nor estimate a range of possible loss. In January 2013, the Company was served with a lawsuit, filed in Belgium by a distributor called Laser 2000 Beneluo SA (“Laser 2000”) claiming unpaid commissions. The distributor agreement was formally terminated as of January 3, 2012. The Company paid $492,000 to Laser 2000 as partial settlement of claims and to avoid penalties from the Court and submitted a legal brief to court on September 16, 2013. Laser 2000 filed a response on December 16, 2013 and the Company filed the final rebuttal brief on January 30, 2014. In March 2015, the Belgian Court issued a ruling awarding Laser 2000 approximately one million euros in damages (approximately $1,100,000 at current exchange rates). The Company did not believe it would ultimately be liable for the full amount of damage and accrued $0.3 million in March 2015 for estimated probable net litigation expense relating to this matter. The Company appealed this verdict and, in April 2017 settled this case and paid approximately $250,000 . In December 2016 the Company was served with a lawsuit filed by Lestina International Ltd. (“Lestina”), in Santa Clara County, CA. The lawsuit is regarding a dispute of approximately $3.0 million related to purchase orders for the Company’s Low Speed Transceiver Products that was soon thereafter sold by the Company to APAT OE in January 2017. The purchase orders in question were included in the asset sale and were assumed liabilities by the purchaser of the business. The parties engaged in extensive negotiations and in January 2019, the parties agreed to a proposed settlement which was placed on the record of the Superior Court of Santa Clara County agreeing that NeoPhotonics Dongguan Co., Ltd. (“NeoDongguan”) (the Company’s wholly owned subsidiary located in China) would pay to Lestina a total of $2.2 million . Upon Lestina's receipt of full payment, Lestina will ship to NeoDongguan the remaining parts from the original purchase orders. The Company has agreed to be a guarantor for NeoDongguan on the payment obligation to Lestina. The $2.2 million settlement shall be paid in two payments of $1.2 million in February 2019 and $1.0 million in June 2019 respectively. In April 2018, APAT OE filed three lawsuits in the Qianhai Court in Shenzhen, China against NeoPhotonics (China) Co., Ltd., NeoPhotonics Dongguan Co. Ltd. (collectively "Neo China") and NeoPhotonics Corporation claiming approximately twenty million US dollars in damages. The lawsuit is in reference to the sale of the low speed transceiver business to APAT OE from NeoChina. APAT OE claims that the business has been losing money and that APAT OE was not given all of the information about the business they purchased prior to signing the Asset Purchase Agreement ("APA"). In May 2018, counsel on behalf of NeoChina filed a motion objecting to the jurisdiction, claiming that the proper jurisdiction for any dispute between these parties is the Shenzhen Court of International Arbitration and the proper parties to this dispute are NeoChina and APAT OE, pursuant to the APA. In June 2018 a hearing was held in the Qianhai Court in Shenzhen, China. In August 2018, the Court ruled in favor of APAT OE. In September 2018, NeoChina filed an appeal with the Intermediate Court of Shenzhen, which held a hearing on the matter in October 2018. At that hearing arguments were heard regarding the proper jurisdiction for all disputes between NeoChina and APAT OE. NeoChina argued that all disputes between the parties should be decided in the Shenzhen Court of Arbitration per the APA between the parties. APAT OE argued that the Qianhai Court is the appropriate jurisdiction. In November 2018 the Intermediate Court of Shenzhen reversed the lower court’s (Qianhai Court of Shenzhen) judgment and ruled that the dispute shall be governed by the Shenzhen Court of International Arbitration, in favor of NeoChina, dismissing in totality the litigation against NeoChina. The litigation continues against the Company; however the Company’s position is that there is no existing contract between APAT OE and the Company and therefore no basis for litigation. The Company is unable to predict the outcome of this matter. In December 2018, APAT OE applied to the Intermediate Court of Shenzhen for a pre-trial preservation order. On the same day the Court issued the order to preserve approximately $29.0 million of Neo China assets. The order is temporary. If APAT OE does not file a lawsuit against NeoChina within 30 days of the order, or if the lawsuit is dismissed the order will then be null and void. In January 2019, there was an additional pre-trial preservation order to preserve approximately $3.8 million of Neo China assets. In the first quarter of 2019, APAT OE filed a lawsuit in the Intermediate Court of Shenzhen against Neo China, NeoPhotonics Corporation Limited (HK), Novel Centennial Limited (BVI) and NeoPhotonics Corporation, asserting claims and damages against all parties in the amount of approximately $36.0 million . The claims include but are not limited to allegations that defendants are responsible for a customer terminating APAT OE’s business, that defendants are responsible for APAT OE’s inability to complete a low speed business-related project and that defendants are responsible for loss of profits by APAT OE using a contract manufacturer that Neo China had been using prior to the sale. The Company is unable to predict the outcome of this matter. APAT Arbitration In June 2017, APAT OE filed an arbitration claim against NeoChina (collectively both of the Company’s China subsidiaries), claiming that approximately $1.5 million of the inventory that was sold to APAT OE by NeoChina in the APA was aged inventory and of no value. NeoChina brought a counterclaim against APAT OE. The arbitration was heard in the Shenzhen Court of International Arbitration in August 2017. In October 2017, NeoChina was informed that they were successful in the defense of the dispute and were also successful in their counterclaim against APAT OE. NeoChina was awarded approximately RMB 700,000 (approximately $110,000 ) in compensatory damages and attorney fees as well as having the approximately $1.5 million claim against NeoChina rejected in its entirety. In April 2018, APAT OE filed a Notice of Judicial Review of the arbitration judgment in the Shenzhen Intermediate Court in Shenzhen, China. The case was heard in May 2018, and NeoChina was successful in disputing the Judicial Review, which means that the arbitration judgment against APAT OE and in favor of NeoChina stands. In July 2018 NeoChina applied together to the Shenzhen Intermediate Court for enforcement of the previous arbitration ruling because APAT OE had refused to perform the arbitral award. In October 2018 the Court enforced the award officially closing this arbitration matter. In July 2018 NeoChina filed an arbitration against APAT OE in the Shenzhen Court of International Arbitration, claiming approximately $12.0 million in damages against APAT OE as related to liability under the APA. This case is awaiting a hearing date. In November 2018, APAT OE filed an additional arbitration against NeoChina and the Company in the Shenzhen Court of International Arbitration, claiming approximately $7.8 million for liability under the APA. This case is awaiting a hearing date. In February 2019, NeoChina filed a claim in the Shenzhen Court of International Arbitration against APAT OE and Zhejiang Merchants Property Insurance Company for losses and damages to NeoChina in the amount of approximately RMB 350,000 related to the recent pre-trial property preservations filed by APAT OE and related legal fees. Indemnifications In the normal course of business, the Company enters into agreements that contain a variety of representations and warranties and provide for general indemnification. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future, but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. In November 2016 Oyster Communications, Inc. filed nine patent lawsuits against several defendants in the U.S. District Court for the Eastern District of Texas, including one against Cisco Systems, Inc ("Cisco"). One defendant successfully transferred their case to the U.S. District Court for the Northern District of California. Additional defendants requested venue changes are still pending. The Company was not named as a defendant in any of the lawsuits. In July 2017, Cisco notified the Company that it would be seeking indemnification from the Company for claims against Cisco arising from the lawsuits and the parties engaged in discussions and negotiations. In September 2018, the Company and Cisco signed a settlement agreement under which the Company agreed to pay to Cisco $300,000 to be paid by January 31, 2019 and $150,000 in product credits to be applied during calendar year 2019. This settlement resolves Cisco's indemnification claims against the Company in this matter. Purchase obligations The Company has open purchase orders with its suppliers for the purchase of inventory and other items in the ordinary course of its business. As of December 31, 2018, the Company’s estimate of outstanding amounts under these purchase orders was approximately $50.9 million , primarily expected to be purchased within the next 12 months. Certain of these open purchase orders may be cancellable without penalty. Penalty Payment Derivative In connection with a private placement transaction with Joint Stock Company "Rusnano" (formerly Open Joint Stock Company “RUSNANO"), or Rusnano, in 2012, the Company agreed to certain performance obligations including establishing a wholly-owned subsidiary in Russia and making a $30.0 million investment commitment (the "Investment Commitment") towards the Company’s Russian operations, which could be partially satisfied by cash and/or non-cash investment inside or outside of Russia and/or by way of non-cash asset transfers. The Rights Agreement as amended in 2015 (the "Amended Rights Agreement") limits the maximum amount of penalties and/or exit fee (the "Rusnano Payment") to be paid by the Company to $5.0 million in the aggregate and allows such payment to be reduced when certain milestones are met over time. The Amended Rights Agreement also provides for an updated investment plan for the Company’s Russian subsidiaries that includes non-cash transfer of licensing rights to intellectual property, non-cash transfers of existing equipment and commitments to complete the remaining investment milestones through 2019. As of December 31, 2018, the remaining Investment Commitment was approximately $6.7 million to be invested at any time on or before December 31, 2019. At any point between December 31, 2018 and December 31, 2019, the Company may elect to pay a $2.0 million exit fee to terminate any remaining obligations associated with the Investment Commitment. Rusnano has non-transferable veto rights over the Company’s Russian subsidiaries’ annual budget during the investment period and must approve non-cash asset transfers to be made in satisfaction of the Investment Commitment. The Company accounted for the Rusnano Payment as an embedded derivative instrument. The fair value of the penalty payment derivative has been estimated at the date of the original common stock sale (April 27, 2012) and at each subsequent balance sheet date using a probability-weighted discounted future cash flow approach using unobservable inputs, which are classified as Level 3 within the fair value hierarchy. The primary inputs for this approach include the probability of achieving the Investment Commitment and a discount rate that approximates the Company’s incremental borrowing rate. After the initial measurement, changes in the fair value of this derivative are recorded in other income (expense), net. The estimated fair value of this derivative was $2.0 million as of December 31, 2018 and $0.4 million as of December 31, 2017. As of December 31, 2018, and December 31, 2017, the derivative was reported within Accrued and other current liabilities and other noncurrent liabilities, respectively on the Company’s consolidated balance sheets. See Note 9. In December 2018, the Company signed a definitive agreement with Rusnano to sell the Company’s 100% interest in NeoPhotonics Corporation, LLC, the subsidiary for the Company’s manufacturing operations in Russia, for approximately book value. The purchase price to be paid by Rusnano will consist of approximately $3.0 million in cash and $1.0 million in cancellation of the remaining penalty payment that would otherwise be owed to Rusnano as consideration for the Company's obligations to provide manufacturing process transition to NeoPhotonics Corporation, LLC.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Stockholders’ Equity	Stockholders’ Equity Common stock As of December 31, 2018, the Company had reserved 7,486,096 shares of common stock for issuance under its stock plans and 474,462 shares of common stock for issuance under its employee stock purchase plan. Resale Registration Statement In December 2014, the Company entered into a Commitment to File a Registration Statement and Related Waiver of Registration Rights, whereby Rusnano waived certain registration rights in connection with a potential offering by the Company of shares of the Company’s common stock, and the Company committed to file with the U.S. Securities and Exchange Commission a resale registration statement on Form S-1 covering the resale of all shares of the Company’s common stock held by Rusnano. In each of 2015 and 2016, the Company filed such resale registration statement, which registered 4,972,905 shares of the Company’s common stock, at a par value of $0.0025 per share, held by Rusnano. The Company does not receive any proceeds from any sales of the Company’s common stock held by Rusnano (See Note 14). Follow-On Public Offering In 2015, the Company completed a follow-on public offering, in which the Company sold 6,866,689 shares of its common stock, including 895,655 shares of common stock sold upon the exercise in full of the overallotment option by the underwriters, at a public offering price of $7.25 per share. The Company raised approximately $45.6 million , net of underwriting discounts of $3.0 million and other offering expenses of approximately $1.2 million . Accumulated Other Comprehensive Income (Loss) The following table shows the components of accumulated other comprehensive income (loss), net of taxes, as of December 31, 2018 and 2017 (in thousands): December 31, 2018 December 31, 2017 Foreign currency translation adjustments $ (6,897 ) $ 567 Unrealized loss on available-for-sale securities — (1 ) Defined benefit pension plan adjustment (229 ) (168 ) $ (7,126 ) $ 398 No material amounts related to available-for-sale securities or the defined benefit pension plan were reclassified out of accumulated other comprehensive income (loss) during the years ended December 31, 2018, 2017 or 2016. Accumulated Deficit Approximately $9.0 million and $8.8 million of the Company’s retained earnings within its accumulated deficit at December 31, 2018 and 2017, respectively, was subject to restriction due to a requirement that its subsidiaries in China set aside at least 10% of their respective accumulated profits each year to fund statutory common reserves as well as allocate a discretional portion of their after-tax profits to their staff welfare and bonus fund.

Stock-based compensation

Stock-based compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation	Stock-based compensation Equity incentive programs 2004 Stock Option Plan In March 2004, the Company adopted the 2004 Stock Option Plan (the “2004 Plan”) for the benefit of its eligible employees, consultants and independent directors. In February 2011, in connection with the closing of the Company’s initial public offering and execution of the associated underwriting agreement, shares authorized for issuance under the 2004 Plan were cancelled (except for those shares reserved for issuance upon exercise of outstanding stock options). As of December 31, 2018, options to purchase 273,685 shares were outstanding under the 2004 Plan and no shares were available for future grant. 2007 Stock Appreciation Grants Plan In October 2007, the Company adopted its 2007 Stock Appreciation Grants Plan (the “2007 Plan”). The 2007 Plan provides for the grant of units (“stock appreciation units”) entitling the holder upon exercise to receive cash in an amount equal to the amount by which the Company’s common stock has appreciated in value. Each stock appreciation unit entitles a participant to a cash payment in the amount of the excess of the fair market value of a share of common stock on the exercise date over the fair market value of a share of common stock on the award date. The total appreciation available to a participant from the exercise of an award is equal to the number of stock appreciation units being exercised, multiplied by the amount of appreciation per stock appreciation unit. The stock appreciation units granted under the 2007 Plan were primarily granted to employees or consultants of the Company’s subsidiaries in China. As of December 31, 2018, 27,872 stock appreciation units were outstanding, all of which were vested. The Company does not intend to grant additional stock appreciation units under the 2007 Plan. 2010 Equity Incentive Plan In April 2010, the Company adopted its 2010 Equity Incentive Plan (the “2010 Plan”). The 2010 Plan will terminate on April 13, 2020, unless sooner terminated by the board of directors. The 2010 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, market-based stock awards, and other forms of equity compensation, or collectively, stock awards, all of which may be granted to employees, including officers, and to non-employee directors and consultants. Additionally, the 2010 Plan provides for the grant of market-based cash awards. Incentive stock options may be granted only to employees. All other awards may be granted to employees, including officers, and to non-employee directors and consultants. Under the terms of the 2010 Plan, awards may be granted at prices not less than 100% of the fair value of the Company’s common stock, as determined by the Company’s board of directors, on the date of grant for an incentive stock option and not less than 85% of the fair value of the Company’s common stock on the date of grant for a non-qualified stock option. Options vest over a period of time as determined by the board of directors, generally over a three to four year period, and expire ten years from date of grant. Initially, the aggregate number of shares of the Company’s common stock that may be issued pursuant to stock awards under the 2010 Plan was 865,420 shares. The number of shares of the Company’s common stock reserved for issuance under the 2010 Plan automatically increase on January 1st each year, starting on January 1, 2012 and continuing through January 1, 2020, by 3.5% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or such lesser number of shares of common stock as determined by the Company’s board of directors. The maximum number of shares that may be issued pursuant to the exercise of incentive stock options under the 2010 Plan is 8,000,000 shares. As of December 31, 2018, stock options to purchase and restricted stock units to convert to a total of 5,553,442 shares of common stock were outstanding under the 2010 Plan and 835,575 shares were reserved for future issuance. 2010 Employee Stock Purchase Plan In February 2011, the Company adopted its 2010 Employee Stock Purchase Plan (the “2010 ESPP”). The 2010 ESPP was implemented through a series of offerings of purchase rights to eligible U.S. employees. The offering period is for 12 months beginning November 16 th of each year, with two purchase dates on May 15 th and November 15 th . The 2010 ESPP initially authorized the issuance of 342,568 shares of the Company’s common stock pursuant to purchase rights granted to employees or to employees of designated affiliates. The number of shares of common stock reserved for issuance automatically increase on January 1st of each year, starting January 1, 2012 and continuing through January 1, 2020, in an amount equal to the lesser of (1) 3.5% of the total number of shares of common stock outstanding on December 31 st of the preceding calendar year, (2) 600,000 shares of common stock or (3) such lesser number of shares of common stock as determined by the Company’s board of directors. As of December 31, 2018, the Company had 474,462 shares reserved for future issuance. 2011 Inducement Award Plan In September 2011, the Company adopted its 2011 Inducement Award Plan (the “2011 Plan”). The 2011 Plan provides for awarding options, stock appreciation rights, restricted stock grants, restricted stock units and other awards to new employees of the Company and its affiliates, including as a result of future business acquisitions. All options under this plan will be designated as non-statutory stock options. The number of shares initially reserved for issuance under the 2011 Plan was 750,000 shares. The exercise price of awards shall be not less than 100% of the fair market value of the Company’s common stock on the date of grant. Each stock appreciation right grant will be denominated in shares of common stock equivalents. Options and stock appreciation rights have a maximum term of ten years measured from the date of grant, subject to earlier termination following the individual’s cessation of service with the Company. In 2015, an additional 100,000 shares were authorized for issuance by the Company’s board of directors. As of December 31, 2018, stock options to purchase and restricted stock units to convert to a total of 556,646 shares of common stock were outstanding under the 2011 Plan and 266,748 shares were reserved for future issuance. Determining Fair Value The Company estimated the fair value of certain stock-based awards using a Black-Scholes-Merton valuation model with the following assumptions: Years ended December 31, Stock options 2018 2017 2016 Weighted-average expected term (years) 6.02 5.99 5.75 Weighted-average volatility 65% 65% 65% Risk-free interest rate 2.27%-2.62% 2.02%-2.08% 1.01%-1.76% Expected dividends — % — % — % Stock appreciation units Weighted-average expected term (years) 1.94 2.30 2.77 Weighted-average volatility 66% 69% 61% Risk-free interest rate 1.03%-2.81% 0.51%-1.62% 0.45%-1.47% Expected dividends 0 — % — % ESPP Weighted-average expected term (years) 0.72 0.72 0.73 Weighted-average volatility 61% 61% 54% Risk-free interest rate 1.93%-2.59% 0.91%-1.31% 0.39%-0.45% Expected dividends — % — % — % Expected term. The expected term for stock options was estimated using the Company’s historical exercise behavior and expected future exercise behavior. Vested stock appreciation units first became exercisable upon the expiration of the lock-up period associated with the initial public offering. Therefore, the Company estimated the term of the award based on an average of the weighted-average exercise period and the remaining contractual term. The expected term for the ESPP represents the period of time from the beginning of the offering period to the purchase date. Volatility. Due to the limited history of the trading of the Company’s common stock since the initial public offering in February 2011, the expected volatility used by the Company was based on a combination of its own volatility and the volatility of similar entities through end of 2016. In evaluating similarity, factors such as industry, stage of life cycle, size, and financial leverage were taken into consideration. The term over which volatility was measured was commensurate with the expected term. Starting 2017, the volatility assumption is based on the historical volatility of our common stock over the expected term of the stock options. Risk-free interest rate . The risk-free rate that the Company uses in the Black-Scholes-Merton option valuation model is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected term on the options. Expected dividends. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future, and, therefore, used an expected dividend yield of zero in the valuation model. Stock-Based Compensation Expense The following table summarizes the stock-based compensation expense recognized for the years ended December 31, 2018, 2017 and 2016. Unamortized stock-based compensation costs capitalized as part of inventory were immaterial in each of the periods presented (in thousands): Years ended December 31, 2018 2017 2016 Cost of goods sold $ 2,596 $ 1,098 $ 3,130 Research and development 3,570 2,491 4,760 Sales and marketing 3,248 1,697 4,105 General and administrative 4,728 2,920 5,081 $ 14,142 $ 8,206 $ 17,076 2014 Stock Option and Stock Appreciation Rights Repricing Offer On December 18, 2014, the Company completed an offer to certain of its current employees (or engaged as a consultant to the Company) to receive the opportunity to reduce the exercise price of certain outstanding eligible options or eligible stock appreciation rights to the closing trading price of the Company’s common stock on December 18, 2014 , in exchange for such holders’ agreement to accept a new vesting schedule (the “Repricing Offer”). The eligible stock options and stock appreciation rights covered an aggregate of 2,373,692 shares of the Company’s common stock. On December 18, 2014, options to purchase 1,948,631 shares of the Company’s common stock and stock appreciation rights to purchase 87,354 shares of the Company’s common stock were repriced in the Repricing Offer. The repriced eligible options and eligible stock appreciation rights had a grant date compensation cost, net of forecasted forfeitures, of approximately $2.6 million , which included incremental compensation cost of approximately $0.9 million . The new exercise price per share for each repriced eligible option or eligible stock appreciation right is $3.50 . Each of the repriced eligible options or eligible stock appreciation rights was subject to a new vesting schedule as follows: 50% of the shares subject to such repriced eligible option or eligible stock appreciation right vested and became exercisable on January 1, 2016, and the remaining 50% vested and became exercisable in 12 equal monthly installments on each monthly anniversary thereafter, in each case subject to continued service with the Company on each applicable vesting date; provided, however, that alternative vesting applied to certain eligible options or eligible stock appreciation rights if the expiration date of such eligible options or eligible stock appreciation rights was after January 30, 2016, but on or before January 1, 2017 , then 50% of the shares subject to the repriced awards vested and became exercisable on January 1, 2016 and the remaining shares were subject to ratable monthly vesting over the remaining term ending 60 days prior to the expiration date of the repriced awards; if the expiration date of such eligible options or eligible stock appreciation rights was prior to January 30, 2016, then 100% of the shares subject to the repriced awards vested and became exercisable on the 60 th day prior to the expiration date. Stock Option and Restricted Stock Unit Activity The following table summarizes the Company’s stock option and restricted stock unit, or RSU, activity during the year ended December 31, 2018: Stock Options Restricted Stock Units Shares Available for Grant Number of Shares Weighted Average Exercise Price Number of Units Weighted Average Grant Date Fair Value Balance at December 31, 2017 959,136 3,933,529 $ 5.55 2,404,637 $ 9.02 Authorized for issuance 1,947,667 — — — — Granted (2,300,056 ) 158,116 6.64 1,446,940 6.83 Exercised/Converted — (778,811 ) 4.39 (1,123,893 ) 8.82 Cancelled/Forfeited 495,576 (110,089 ) 10.07 (241,656 ) 8.74 Balance at December 31, 2018 1,102,323 3,202,745 $ 5.73 2,486,028 $ 7.87 The following table summarizes information about stock options outstanding as of December 31, 2018: Options Outstanding Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in Thousands) Vested and expected to vest 3,152,837 $ 5.70 5.31 $ 4,936,208 Exercisable 2,701,433 $ 5.32 4.78 $ 4,864,959 The fair value of options vested during the years ended December 31, 2018, 2017 and 2016 was $2.3 million , $1.5 million and $3.9 million , respectively. The intrinsic value of options vested and expected to vest and exercisable as of December 31, 2018 is calculated based on the difference between the exercise price and the fair value of the Company’s common stock as of December 31, 2018. The intrinsic value of options exercised during the years ended December 31, 2018, 2017 and 2016, was $2.4 million , $3.0 million and $9.7 million , respectively. The weighted-average fair value of options granted was $4.03 , $4.43 and $7.05 per share for the years ended December 31, 2018, 2017 and 2016, respectively. At December 31, 2018, there was $1.8 million of unrecognized stock-based compensation expense for stock options, net of estimated forfeitures, which will be recognized over the remaining weighted-average period of 1.8 years. Included in the outstanding stock options at December 31, 2018 are 0.8 million shares of market-based stock options granted to key personnel. The fair value of its market-based option grants was $4.72 for 2015 and $1.65 for 2014 using a Monte Carlo simulation model with the assumptions discussed above. These options vested in September 2016 as a result of the satisfaction of the market condition requiring the average closing price of the Company’s common stock over a period of 20 consecutive trading days to be equal to or greater than $15.00 per share and the recipients remaining in continuous service with the Company through such period. The Company recorded approximately $4.8 million in related stock-based compensation expense for these options in 2016. The following table summarizes information about RSUs outstanding as of December 31, 2018: Restricted Stock Units Outstanding Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in Thousands) Vested and expected to vest 2,166,565 $ — 1.26 $ 14,039,340 The fair value of RSUs vested during the years ended December 31, 2018, 2017 and 2016 was $9.8 million , $7.6 million and $1.6 million , respectively. The intrinsic value of RSUs vested and expected to vest as of December 31, 2018 is calculated based on the fair value of the Company’s common stock as of December 31, 2018. The intrinsic value of RSUs converted during the years ended December 31, 2018, 2017 and 2016, was $7.4 million , $6.4 million and $2.8 million , respectively. The weighted-average fair value of RSUs granted was $6.83 , $7.86 and $12.33 per share for the years ended December 31, 2018, 2017 and 2016, respectively. At December 31, 2018, the Company had $13.2 million of unrecognized stock-based compensation expense for RSUs, net of estimated forfeitures, which will be recognized over the remaining weighted-average period of 2.1 years. The majority of the Company’s RSUs that were converted during the years ended December 31, 2018, 2017 and 2016 were net share settled. Upon each settlement date, RSUs were withheld to cover the minimum withholding tax and the remaining amounts were delivered to the recipient as shares of the Company’s common stock. In 2018, 2017 and 2016, the Company withheld 147,572 , 126,999 and 49,838 shares, respectively, and remitted cash of $1.0 million , $1.0 million and $0.6 million , respectively, to the appropriate tax authorities. Market-based Restricted Stock Unit Activity In 2018, the Company granted 695,000 shares of market-based RSUs to certain employees. These RSUs will vest if the 30-day weighted average closing price of the Company's common stock is equal to or greater than certain price targets per share and the recipients remain in continuous service with the Company through such service period. No market-based RSUs were vested/cancelled during 2018. The weighted average grant-date fair value per share of market-based RSUs granted during 2018 was approximately $5.82 per share. As of December 31, 2018, the Company had $2.9 million of unrecognized stock-based compensation expense for RSUs, net of estimated forfeitures, which will be recognized over the remaining weighted-average period of 3.5 years. The fair value of market-based RSUs was measured on the grant date using Monte Carlo simulation model with the following assumptions: Years ended December 31, 2018 2017 Weighted-average volatility 66% —% Risk-free interest rate 2.79% —% Expected dividends —% —% Market-based RSUs expire seven years from the date of grant. As of December 31, 2018, the weighted average remaining contractual term for market-based RSUs is 6.5 years. Stock Appreciation Unit Activity The following table summarizes the Company’s stock appreciation unit activity during the year ended December 31, 2018: Stock Appreciation Units Weighted-Average Exercise Price Stock appreciation units outstanding as of December 31, 2017 239,824 $ 4.95 Stock appreciation units exercised (31,272 ) $ 4.32 Stock appreciation units cancelled (15,680 ) $ 6.72 Stock appreciation units outstanding as of December 31, 2018 192,872 $ 4.91 The fair value of stock appreciation units vested was immaterial in 2018 and 2017 and $3.7 million in 2016. The intrinsic value of stock appreciation units is calculated based on the difference between the exercise price and the fair value of the Company’s common stock as of December 31, 2018. Cash paid for stock appreciation units exercised was $0.1 million in 2018, $0.2 million in 2017, and $0.5 million in 2016. As of December 31, 2018 and 2017, the liability for settlement of stock appreciation units was approximately $0.6 million and $0.8 million , respectively, and was included in accrued and other current liabilities on the consolidated balance sheet, based on the fair value of the stock appreciation units, that will be recognized through settlement. Included in the outstanding stock appreciation units at December 31, 2018 were 0.2 million shares of market-based stock appreciation units granted to key personnel which were granted during 2013. These market-based units vested in September 2016 upon the satisfaction of the market condition requiring the average closing price of the Company’s common stock over a period of 20 consecutive trading days to be equal to or greater than $15.00 per share and the recipients remaining in continuous service with the Company through such period. In 2018, the Company recorded approximately $0.1 million gain as compared to approximately $0.3 million gain in 2017, in related stock-based compensation for these stock appreciation units. Employee Stock Purchase Plan The Company issued 404,211 shares under the 2010 ESPP during the year ended December 31, 2018. As of December 31, 2018, there was $0.8 million of unrecognized stock-based compensation expense for stock purchase rights that will be recognized over the remaining offering period, through November 2019.

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income taxes	Income taxes - The provision for income taxes is based upon the income (loss) before income taxes as follows (in thousands): Years Ended December 31, 2018 2017 2016 U.S. operations $ (43,384 ) $ (52,725 ) $ (10,217 ) Non-U.S. operations 1,076 301 13,609 $ (42,308 ) $ (52,424 ) $ 3,392 The components of the provision for income taxes consisted of the following (in thousands): Years Ended December 31, 2018 2017 2016 Current Federal $ (49 ) $ (144 ) $ (127 ) State 36 3 (13 ) Foreign (1,634 ) 363 (3,925 ) (1,647 ) 222 (4,065 ) Deferred Federal 42 4 (24 ) State — — — Foreign 276 (1,135 ) 492 Total provision $ (1,329 ) $ (909 ) $ (3,597 ) The provision for income taxes differs from the amount obtained by applying the U.S. federal statutory tax rate as follows (in thousands, except percentages): Years Ended December 31, 2018 2017 2016 Federal statutory rate 21 % 35 % 35 % Tax at federal statutory rate $ 8,869 $ 18,354 $ (1,185 ) State taxes, net of federal benefit 36 2 (8 ) Mandatory repatriation/Section 956 — (5,718 ) (19 ) Nondeductible expenses (371 ) (67 ) (727 ) Stock-based compensation (1,079 ) (314 ) (877 ) Change in valuation allowance (10,094 ) 16,273 (1,455 ) Research and development 914 851 1,175 Foreign rate differences (697 ) (2,819 ) (1,215 ) Foreign tax credit 49 144 127 Change in prior year deferred balances 1,653 (28,262 ) 920 Other (609 ) 647 (333 ) Total provision for income taxes from continuing operations $ (1,329 ) $ (909 ) $ (3,597 ) Change in prior year deferred balances of $28.3 million include approximately $30.0 million related to remeasurement of U.S. federal deferred tax assets from corporate tax rate of 35% to 21%, based on the newly enacted tax laws in December 2017. See below for more discussion related to newly enacted tax laws in December 2017. Deferred income tax assets and liabilities comprise the following (in thousands): December 31, 2018 2017 Deferred Tax Assets: Net operating loss carryforwards $ 56,828 $ 44,912 Federal and state credits 28,328 26,170 Reserves, accruals and other 11,265 9,698 Fixed assets and intangibles 2,398 1,259 Total deferred tax assets 98,819 82,039 Valuation allowance (92,891 ) (76,101 ) Total deferred tax assets, net of valuation allowance 5,928 5,938 Less deferred tax liabilities: Acquired intangibles (313 ) (2,054 ) Property, plant and equipment (4,754 ) (3,338 ) Net deferred tax assets $ 861 $ 546 Reported as: Long term deferred tax assets, included within other long-term assets $ 861 $ 652 Long term deferred income tax liabilities, included within noncurrent liabilities — (106 ) Net deferred tax assets $ 861 $ 546 The net valuation allowance increased by $16.8 million in 2018 and decreased by $14.0 million in 2017. The increase of valuation allowance in 2018 was due to increase in US deferred tax assets, while the decrease of valuation allowance in 2017 was due to remeasurement of US deferred tax assets based on a reduced tax rate of 21% from 35%. The Company did not record a full valuation allowance against its net deferred tax assets in most foreign jurisdictions as it believes these deferred tax assets were realizable on a more likely than not basis as of December 31, 2018. Based upon the weight of available evidence, which includes the Company’s historical operating performance and the reported cumulative net losses to date, the Company continues to maintain a full valuation allowance against its net U.S. deferred tax assets. The Company adopted ASU 2016-16 on a modified retrospective basis effective January 1, 2018. Upon adoption of this standard on January 1, 2018, the Company recorded $1.8 million to accumulated deficit balance for intra-entity transfer of an asset other than inventory in prior years. The Company adopted ASU 2016-9 effective January 1, 2017. Upon adoption, the Company's previously unrecognized excess tax benefits of $8.6 million had no impact on its accumulated deficit balance as the related U.S. deferred tax assets were fully offset by a valuation allowance. As of December 31, 2018, the Company had federal and state net operating loss, or NOL, carryforwards of $276.6 million and $52.0 million , respectively. Federal NOL carryforwards start to expire in 2022 and a portion of the California NOL carryforwards will begin to expire in 2028. As of December 31, 2018, the Company also had federal and state research and development tax credit carryovers of $9.4 million and $17.3 million , respectively. The federal credits will begin to expire in 2019 and the state credits can be carried forward indefinitely. The Company also had $10.5 million of foreign tax credit carryforwards which will start to expire in 2022 if not utilized. Utilization of NOL carryforwards and carried over tax credits may be subject to substantial annual limitation due to federal and state ownership limitations. The annual limitation may result in the expiration of NOL and tax credit carryforwards before utilization. The deferred tax assets listed above do not include NOL carryforwards that are expected to expire unutilized as a result of existing ownership changes. On December 22, 2017, the Tax Cuts and Jobs Act (the “TCJA”) was enacted which, among other things, lowered the U.S. federal corporate income tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and creates Global Intangible Low Taxed Income ("GILTI") to tax certain foreign sourced earnings. As of December 31, 2018, the Company has concluded the accounting under the TCJA within the time period set forth in Staff Accounting Bulletin 118. There was no provision impact of TCJA on the 2018 consolidated financial statements due to full valuation allowance on US deferred tax assets. In addition, the Company has elected to treat GILTI inclusion accounting impact as a current period expense. The Company continues the assertion to permanently reinvest its foreign earnings. At December 31, 2018, the Company’s gross unrecognized tax benefits were approximately $26.2 million , of which $0.1 million would impact the effective tax rate if recognized. Substantial portion of these unrecognized tax benefits could be subject to a valuation allowance if and when recognized in a future period, which could impact the timing of any related effective tax rate benefit. The Company does not believe that the amount of unrecognized tax benefits will change significantly in the next twelve months. There were no interest or penalties related to unrecognized tax benefits. The Company’s policy is to classify interest and penalties associated with unrecognized tax benefits as income tax expense. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Balance at December 31, 2015 $ 20,686 Gross increases for tax positions of current year 2,920 Balance at December 31, 2016 23,606 Gross increases for tax positions of current year 1,933 Balance at December 31, 2017 25,539 Gross increases for tax positions of current year 657 Balance at December 31, 2018 $ 26,196 The Company’s material tax jurisdictions are the United States federal, California, Japan and China. As a result of NOL carryforwards, substantially all of the Company’s tax years remain open to U.S. federal and state tax examination. Tax years for 2012 and forward remain open for Chinese tax examination.

Segment and geographic informat

Segment and geographic information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment and geographic information	Segment and geographic information The Company’s Chief Executive Officer, who is considered to be the chief operating decision maker, manages the Company’s operations as a whole and reviews financial information presented on a consolidated basis for purposes of evaluating financial performance and allocating resources. In 2018, 2017 and 2016, the Company operated in one reportable segment. Through 2018, the Company has aligned its products to High Speed Products and Network Products and Solutions (see Note 3). The following tables set forth the Company’s asset information by geographic region (in thousands): As of December 31, 2018 2017 Property, plant and equipment, net: China $ 27,329 $ 37,212 United States 29,054 42,243 Japan 29,631 43,826 Rest of world 14,076 4,284 Total $ 100,090 $ 127,565

Selected Quarterly Financial Da

Selected Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Selected Quarterly Financial Data (unaudited)	Selected Quarterly Financial Data (unaudited) The following tables set forth a summary of the Company’s quarterly financial information for each of the four quarters for the years ended December 31, 2018 and 2017: Year ended December 31, 2018 First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share data) Revenues $ 68,586 $ 81,102 $ 81,748 $ 91,104 Gross profit 9,182 15,472 18,933 22,586 Net loss (18,246 ) (10,537 ) (8,125 ) (6,729 ) Basic net loss per share $ (0.41 ) $ (0.24 ) $ (0.18 ) $ (0.15 ) Diluted net loss per share $ (0.41 ) $ (0.24 ) $ (0.18 ) $ (0.15 ) Weighted averages shares used to compute basic net loss per share 44,259 44,665 45,476 46,150 Weighted averages shares used to compute diluted net loss per share 44,259 44,665 45,476 46,150 Year ended December 31, 2017 First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share data) Revenues $ 71,688 $ 73,214 $ 71,121 $ 76,871 Gross profit 18,503 16,777 10,513 15,686 Net loss (11,522 ) (9,341 ) (18,187 ) (14,283 ) Basic net loss per share $ (0.27 ) $ (0.22 ) $ (0.42 ) $ (0.32 ) Diluted net loss per share (0.27 ) (0.22 ) (0.42 ) (0.32 ) Weighted averages shares used to compute basic net loss per share 42,615 43,219 43,790 44,079 Weighted averages shares used to compute diluted net loss per share 42,615 43,219 43,790 44,079

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Subsequent events included the following: In January 2019, the Company repaid $5.0 million to Wells Fargo under the Credit Facility. In January 2019, the Company and Lestina signed a settlement agreement under which the Company agreed to pay Lestina $2.2 million in cash (see Note 14). In January 2019, the Company announced the end-of-life of certain client transceiver modules and therefore will discontinue the manufacture and sale of those products after completing final production in May 2019. This will result in accelerated depreciation of approximately $3.0 million , to be amortized over the final production during the first and second quarters of 2019. In the first quarter of 2019, APAT OE filed a lawsuit in the Intermediate Court of Shenzhen against Neo China, NeoPhotonics Corporation Limited (HK), Novel Centennial Limited (BVI) and NeoPhotonics Corporation, asserting claims and damages against all parties (see Note 14). In February 2019, NeoChina filed a claim against APAT OE in the Shenzhen Court of International Arbitration (see Note 14).

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Use of estimates	Use of estimates The preparation of financial statements in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported revenue and expenses during the reporting period. Significant estimates made by management include: the useful lives of property, plant and equipment and intangible assets as well as future cash flows to be generated by those assets; fair values of identifiable assets acquired and liabilities assumed in business combinations; allowances for doubtful accounts; valuation allowances for deferred tax assets; write off of excess and obsolete inventories; the valuation of the Rusnano payment derivative and the valuations and recognition of stock-based compensation, among others. Actual results could differ from these estimates.
Concentration of credit risk and significant customers	Concentration of credit risk and significant customers Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash and cash equivalents and trade accounts receivable. The Company’s investment policy requires cash and cash equivalents to be placed with high-credit quality institutions and limits on the amount of credit risk from any one issuer. The Company performs ongoing credit evaluations of its customers’ financial condition whenever deemed necessary and generally does not require collateral. The Company maintains an allowance for doubtful accounts based upon the expected collectability of all accounts receivable, which takes into consideration an analysis of historical bad debts, specific customer creditworthiness and current economic trends.
Restricted cash	Restricted cash As a condition of the notes payable lending arrangements and the line of credit facilities, the Company is required to keep a compensating balance at the issuing banks. In addition, the Company also maintained restricted cash in connection with the asset purchase agreement executed in December 2016 (see Note 10), government grants received in advance and cash balances temporarily restricted for regular business operations until a legal dispute is resolved (see Note 14). These balances have been excluded from the Company’s cash and cash equivalents balance and are classified as restricted cash in the Company’s consolidated balance sheets.
Cash, cash equivalents and investments	Cash, cash equivalents and investments Highly liquid investments with a maturity of 90 days or less at the date of purchase are considered cash equivalents, with the exception of money market funds and commercial paper which are classified as short-term investments. Marketable securities are reported at fair value and are classified as available-for-sale investments in our current assets because they represent investments of cash available for current operations and for strategic reasons. As a result, the Company recorded all its marketable securities in short-term investments regardless of the contractual maturity date of the securities. The Company regularly reviews its investment portfolio to identify and evaluate investments that have indications of possible impairment. Factors considered in determining whether a loss is other-than-temporary include: the length of time and extent to which the fair market value has been lower than the cost basis, the financial condition and near-term prospects of the investee, credit quality, likelihood of recovery, and the Company’s ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in fair market value. Unrealized gains and losses, net of tax, are included in accumulated other comprehensive loss as a separate component of stockholders’ equity on the consolidated balance sheets. The amortization of premiums and discounts on the investments, and realized gains and losses on available-for-sale securities are included in other income, net in the consolidated statements of operations. The Company uses the specific-identification method to determine cost in calculating realized gains and losses upon the sale of its marketable securities.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price at which an asset could be exchanged in a current transaction between knowledgeable, willing parties. A liability’s fair value is defined as the amount that would be paid to transfer the liability to a new obligor, not the amount that would be paid to settle the liability with the creditor. Where available, fair value is based on observable market prices or parameters or derived from such prices or parameters. Where observable prices or inputs are not available, valuation models are applied. These valuation techniques involve some level of management estimation and judgment, the degree of which is dependent on the price transparency for the instruments or market and the instruments’ complexity. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative accounting guidance describes a fair value hierarchy based on three levels of inputs that may be used to measure fair value, of which the first two are considered observable and the last is considered unobservable. These levels of inputs are as follows: Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3—Unobservable inputs that reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. For marketable securities measured at fair value using Level 2 inputs, the Company reviews trading activity and pricing for these investments as of the measurement date. When sufficient quoted pricing for identical securities is not available, the Company uses market pricing and other observable market inputs for similar securities obtained from various third party data providers. These inputs either represent quoted prices for similar assets in active markets or have been derived from observable market data.
Accounts receivable	Accounts receivable Accounts receivable include trade receivables and notes receivable from customers. The notes are generally due within nine months . The Company receives notes receivable in exchange for accounts receivable from certain customers in China that are secured by the customer’s affiliated financial institution. An allowance for doubtful accounts is calculated based on the aging of the Company’s trade receivables, historical experience, and management judgment. The Company writes off trade receivables against the allowance when management determines a balance is uncollectible and is no longer actively pursuing collection of the receivable.
Inventories	Inventories Inventories consist of on-hand raw materials, work-in-progress inventories and finished goods. Raw materials and work-in-progress inventories are stored mainly on the Company’s premises. Finished goods are stored on the Company’s premises as well as on consignment at certain customer sites. Inventories are stated at the lower of standard cost, which approximates actual cost determined on the weighted average basis, or net realizable value. Inventories are recorded using the first-in, first-out method. The Company routinely evaluates quantities and values of inventories in light of current market conditions and market trends, and records a write-down for quantities in excess of demand and product obsolescence. The evaluation may take into consideration historic usage, expected demand, anticipated sales price, new product development schedules, the effect new products might have on the sale of existing products, product obsolescence, customer concentrations, product merchantability and other factors. Market conditions are subject to change and actual consumption of inventory could differ from forecasted demand. The Company also regularly reviews the cost of inventories against their estimated market value and records a lower of cost or market write-down for inventories that have a cost in excess of estimated market value, resulting in a new cost basis for the related inventories which is not reversed.
Business Combinations	Business Combinations We allocate the fair value of purchase consideration to the tangible and intangible assets acquired and liabilities assumed based on their estimated fair values as of the close of acquisition. The excess of the fair value of purchase consideration over the fair values of these identifiable assets and liabilities is recorded as goodwill. When determining the fair values of assets acquired and liabilities assumed, management makes significant estimates and assumptions through established and generally accepted valuation techniques. Fair value estimates are based on the assumptions management believes a market participant would use in pricing the asset or liability. Critical estimates in valuing certain intangible assets include, but are not limited to, future expected cash flows from customer relationships and acquired patents and developed technology as well as discount rates. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. Amounts recorded in a business combination may change during the measurement period, which is a period not to exceed one year from the date of acquisition, as additional information about conditions existing at the acquisition date becomes available.
Goodwill	Goodwill Goodwill is reviewed for impairment annually in the fourth fiscal quarter or more frequently if events or changes in circumstances indicate that the carrying value of goodwill may not be recoverable. The Company will assess the qualitative factors to determine whether it is more likely than not that the fair value of its reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step goodwill impairment. If the Company determines that it is more likely than not that its fair value is less than its carrying amount, then the two-step goodwill impairment test is performed. The first step, identifying a potential impairment, compares the fair value of the reporting unit with its carrying amount. If the carrying amount exceeds its fair value, the second step would need to be performed; otherwise, no further steps are required. The second step, measuring the impairment loss, compares the implied fair value of the goodwill with the carrying amount of the goodwill. Any excess of the goodwill carrying amount over the implied fair value is recognized as an impairment loss, and the carrying value of goodwill is written down to fair value.
Long-lived assets	Long-lived assets Property, plant and equipment are stated at cost, net of accumulated depreciation and amortization. Repairs and maintenance costs are expensed as incurred. Depreciation and amortization are computed using the straight-line method over the following estimated useful lives: Buildings 20-30 years Machinery and equipment 2-7 years Furniture, fixtures and office equipment 3-5 years Software 5-7 years Leasehold improvements life of the asset or lease term, if shorter Intangible assets acquired in a business combination are recorded at fair value. Identifiable finite-lived intangible assets are amortized over the period of estimated benefit using the straight-line method, reflecting the pattern of economic benefits associated with these assets. The estimated useful lives of the Company’s finite-lived intangible assets generally range from two to seven years. The acquired land use rights in China have an estimated useful life of 45 years. Assets held for sale are measured at the lower of carrying value or the fair value less cost to sell. The carrying value of intangible assets and other long-lived assets is reviewed on a regular basis for the existence of facts or circumstances, both internally and externally, that may suggest impairment. Some factors which the Company considers to be triggering events for impairment review include a significant decrease in the market value of an asset, a significant change in the extent or manner in which an asset is used, a significant adverse change in the business climate that could affect the value of an asset, an accumulation of costs for an asset in excess of the amount originally expected, a current period operating loss or cash flow decline combined with a history of operating loss or cash flow uses or a projection that demonstrates continuing losses and a current expectation that, it is more likely than not, a long-lived asset will be disposed of at a loss before the end of its estimated useful life. If one or more of such facts or circumstances exist, the Company will evaluate the carrying value of long-lived assets to determine if impairment exists by comparing it to estimated undiscounted future cash flows over the remaining useful life of the assets. If the carrying value of the assets is greater than the estimated future cash flow, the assets are written down to the estimated fair value. The Company’s cash flow estimates contain management’s best estimates, using appropriate and customary assumptions and projections at the time. Any write-down would be treated as a permanent reduction in the carrying amount of the asset and an operating loss would be recognized.
Product warranties	Product warranties The Company generally provides warranties to cover defects in workmanship, materials and manufacturing for a period of one to three years to meet the stated functionality as agreed to in each sales arrangement. Products are tested against specified functionality requirements prior to delivery, but the Company nevertheless from time to time experiences claims under its warranty guarantees. The Company accrues for estimated warranty costs under those guarantees based upon historical experience, and for specific items, at the time their existence is known and the amounts are determinable.
Research and development	Research and development Research and development expense consists of personnel costs, including stock-based compensation expense, for the Company’s research and development personnel and product development costs, including engineering services, development software and hardware tools, depreciation of capital equipment and facility costs. Research and development costs are expensed as incurred.
Advertising costs	Advertising costs Advertising costs are expensed as incurred and, to date, have not been significant.
Stock-based compensation	Stock-based compensation The Company grants stock-based awards to employees, consultants and directors. The stock-based awards, including stock options, restricted stock units, employee stock purchase rights, stock appreciation units and market-based awards, are accounted for at estimated fair values. Vesting of stock-based awards is generally subject to the grantee’s continuing service to the Company. The Company generally determines the fair value of stock options and stock appreciation rights utilizing the Black-Scholes-Merton option-pricing model, or a lattice-binomial option-pricing model for stock-based awards with a market condition. The fair value of employee grants is measured on the date of grant and then recognized over the period during which an employee is required to provide services in exchange for the award, known as the requisite service period (usually the vesting period) on a straight-line basis. The fair value of non-employee grants is measured on the date of grant and then marked to market until vest dates and then recognized over the requisite service period. The Company records expense and an equal adjustment to the liability for stock appreciation units equal to the fair value of the vested portion of the awards as of each period end. Each reporting period thereafter, compensation expense will be recorded based on the remaining service period and the then fair value of the award until vesting of the award is completed. After vesting is completed, the Company will continue to re-measure the fair value of the liability each reporting period until the award is exercised or expires, with changes in the fair value of the liability recorded in the consolidated statements of operations. Restricted stock units are valued at the closing sales price as quoted on the New York Stock Exchange on the date of grant, and are converted into shares of common stock upon vesting on a one-for-one basis. The compensation expense related to the restricted stock units is determined using the fair value of common stock on the date of grant, and the expense is recognized on a straight-line basis over the vesting period. Employee stock purchase rights are accounted for at fair value, utilizing the Black-Scholes-Merton option-pricing model. Stock-based compensation expense for modified stock-based awards are recognized using the pool approach, under which the remaining compensation cost from the original awards plus the incremental costs, if any, of the related modified awards is recognized in its entirety over the remaining portion of the requisition service period of the corresponding modified awards. Stock-based compensation expense recognized at fair value includes the impact of estimated forfeitures. The Company estimates future forfeitures at the date of grant and revises the estimates, if necessary, in subsequent periods if actual forfeitures differ from those estimates.
Income taxes	Income taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the carrying amounts of existing assets and liabilities in the financial statements and their respective tax bases, and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities from a change in tax rates is recognized in the consolidated statement of operations in the period that includes the enactment date. The Company operates in various tax jurisdictions and is subject to audit by various tax authorities. In preparing the Company’s consolidated financial statements, the Company is required to estimate its taxes in each of the jurisdictions in which it operates. The Company estimates actual current tax exposure as well as assesses temporary differences resulting from different treatment of items, such as accruals and allowances not currently deductible for tax purposes. These differences result in deferred tax assets which represent future tax benefits to be received when certain expenses previously recognized in the financial statements become deductible expenses under applicable income tax laws, or loss credit carryforwards are utilized. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of a deferred tax asset will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. A valuation allowance is recorded for loss carryforwards and other deferred tax assets where it is more likely than not that such deferred tax assets will not be realized. The Company classifies its net deferred tax assets as other long-term assets and deferred tax liabilities as noncurrent liabilities on its consolidated balance sheet.
Foreign currency	Foreign currency Generally the functional currency of the Company’s international subsidiaries is the local currency. The Company translates the financial statements of these subsidiaries to U.S. dollars using month-end rates of exchange for assets and liabilities, and average rates of exchange for revenue, costs, and expenses. Translation gains and losses are recorded in accumulated other comprehensive income (loss) as a component of stockholders’ equity. Effective July 1, 2016, the Company has established a hedging program using monthly forward exchange contracts as economic hedges to protect against volatility of foreign exchange rate exposure of its net intercompany activities based on a cost-benefit analysis that considers that magnitude of the exposure, the volatility of the exchange rate and the cost of the hedging instruments. The forward contracts are not designated for hedge accounting and are marked to market at fair value and reported as either other current assets or accounts payable. Any changes in the fair value are recorded as foreign exchange gain (loss) and help mitigate the changes in the value of the underlying net intercompany balances. The Company recognized a $2.2 million loss and $2.1 million gain in 2018 and 2017, respectively, relating to its foreign currency contracts within other income, net. Net foreign exchange gain (loss) was $1.4 million , $(0.5) million , and $(0.1) million in 2018, 2017, and 2016, respectively. These gains and losses were recorded as other income, net in the Company’s consolidated statements of operations. The Company presents the cash flows relating to these foreign exchange contracts as investing activities in its consolidated statements of cash flows. During the six months ended December 31, 2018, the Company temporarily discontinued entering into forward exchange contracts. This may increase the risks to us arising from the short-term impact of foreign currency fluctuations.
Net income (loss) per share	Net income (loss) per share Basic net income (loss) per share is calculated by dividing net income (loss) by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per share is calculated by dividing net income (loss) by the weighted average number of common shares and potential dilutive common share equivalents outstanding during the period if the effect is dilutive.
Accounting standards update recently adopted and not yet effective	Accounting standards update recently adopted Effective January 1, 2017, the Company adopted ASU 2016-9, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-9”). ASU 2016-9 simplifies certain aspects of the accounting for shared-based payment transactions, including income taxes, classification of awards and classification in the statement of cash flows. It eliminates the requirement to delay the recognition of excess tax benefits until current taxes payable are reduced. Upon adoption, the Company’s previously unrecognized excess tax benefits of $8.6 million had no impact on its accumulated deficit balance as the related U.S. deferred tax assets were fully offset by a valuation allowance. The Company elected to apply the change in presentation in the statements of cash flows prospectively and elected to continue to account for estimated forfeitures over the vesting period of the share-based awards. In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-9, Revenue from Contracts with Customers (“ASU 2014-9”). The standard, along with the amendments issued in 2016 and 2015, provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. ASU 2014-9 is required to be adopted, using either of two methods: (i) retrospective to each prior reporting period presented with the option to elect certain practical expedients as defined within ASU 2014-9; or (ii) retrospective with the cumulative effect of initially applying ASU 2014-9 recognized at the date of initial application and providing certain additional disclosures. This standard, as amended, is effective for annual and interim periods beginning after December 15, 2017 and permits entities to early adopt for annual and interim reporting periods beginning after December 15, 2016. The Company adopted this standard as of January 1, 2018, using the full retrospective transition method. See Note 3 for more details. In May 2017, the FASB issued ASU No. 2017-9, Compensation—Stock Compensation (718)— Scope of Modification Accounting (ASU 2017-9”). This guidance redefines which changes to the terms and conditions of a share-based payment award require an entity to apply modification accounting for a share-based payment. ASU 2017-9 is effective for interim and annual periods after December 15, 2017 and early adoption is permitted in any interim period. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In January 2017, the FASB issued ASU 2017-1, Business Combinations (Topic 805) : Clarifying the Definition of a Business (“ASU 2017-1”). This standard provides a framework in determining when a set of assets and activities is a business. ASU 2017-1 is effective for interim and annual periods beginning after December 15, 2017 on a prospective basis. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASC 2016-18”). This standard provides guidance on the classification and presentation of restricted cash in the statement of cash flows and must be applied retrospectively. ASU 2016-18 is effective for fiscal years beginning after December 15, 2017. The Company adopted this standard effective January 1, 2018. The reclassified restricted cash balances from investing activities to changes in cash, cash equivalents and restricted cash on the condensed consolidated statements of cash flows were not material for all periods presented. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). This standard provides guidance on the tax accounting for the transferring and receiving entities upon transfer of an asset. ASU 2016-16 is effective for the Company’s interim and annual periods beginning after December 15, 2017 and should be applied on a modified retrospective basis. Upon adoption of this standard on January 1, 2018, the Company recorded $1.8 million to accumulated deficit balance for intra-entity transfer of an asset other than inventory in prior years. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). This standard provides guidance on the classification of certain cash receipts and payments in the statement of cash flows. It is effective, retrospectively, for the Company’s annual and interim reporting periods beginning after December 15, 2017 or prospectively from the earliest date practicable if retrospective application is impracticable. The Company adopted this standard effective January 1, 2018, using the retrospective transition method. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In January 2016, the FASB issued ASU 2016-1, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-1”). ASU 2016-1 revises an entity’s accounting related to (1) the classification and measurement of investments in equity securities and (2) the presentation of certain fair value changes for financial liabilities measured at fair value. It also amends certain disclosure requirements associated with the fair value of financial instruments and is effective for the Company’s annual and interim reporting periods beginning after December 15, 2017. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In March 2017, the FASB issued ASU No. 2017-7, Compensation-Retirement Benefits (Topic 715)-Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (“ASU 2017-7”). This guidance revises the presentation of employer-sponsored defined benefit pension and other postretirement plans for the net periodic benefit cost in the statement of operations and requires that the service cost component of net periodic benefit be presented in the same income statement line items as other employee compensation costs for services rendered during the period. The other components of the net benefit costs are required to be presented in the statement of operations separately from the service cost component and outside the subtotal of income from operations. This guidance allows only the service cost component of net periodic benefit costs to be eligible for capitalization. ASU 2017-7 is effective for interim and annual periods after December 15, 2017. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. Recent accounting standards update not yet effective In January 2017, the FASB issued ASU 2017-4, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (“ASU 2017-4”). This standard amends the goodwill impairment test to compare the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, up to the total amount of goodwill allocated to that reporting unit. ASU 2017-4 is effective prospectively for interim and annual periods beginning after December 15, 2019. Early adoption is permitted for interim and annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company has not determined whether it will elect early adoption and is currently evaluating the impact of the adoption of this standard on its consolidated financial statements and related disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 amends existing guidance on the impairment of financial assets and adds an impairment model that is based on expected losses rather than incurred losses and requires an entity to recognize as an allowance its estimate of expected credit losses for its financial assets. An entity will apply this guidance through a cumulative-effect adjustment to retained earnings upon adoption (a modified-retrospective approach) while a prospective transition approach is required for debt securities for which an other-than-temporary impairment had been recognized before the effective date. It is effective for the Company’s annual and interim reporting periods beginning after December 15, 2019. Early adoption is permitted. The Company is in the process of evaluating the impact of the adoption on its consolidated financial statements and related disclosure. In February 2016, the FASB issued ASU 2016-2, Leases (Topic 842) (“ASU 2016-2”). ASU 2016-2 introduces a lessee model that requires recognition of assets and liabilities arising from qualified leases on the consolidated balance sheets and consolidated statements of operations and to disclose qualitative and quantitative information about lease transactions. It is effective for interim and annual periods beginning after December 15, 2018. Early adoption is permitted. Certain optional practical expedients allowed. The Company will adopt this standard in the first quarter of 2019, using the modified retrospective transition method and recording a cumulative-effect balance sheet adjustment. The Company has completed the identification of qualified leases. The Company is currently in the process of measuring the right to use assets and lease liabilities on the date of adoption for the qualified leases. The adoption of this guidance is expected to have a material impact on the Company's consolidated balance sheets and disclosures in consolidated financial statements. However, the adoption of this standard is not expected to have a material impact on the Company's consolidated statement of operations.

Summary of significant accoun_3

Summary of significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of Product Information	Customers accounting for more than 10% of our total revenue and revenue from our top five customers for the years ended December 31, 2018, 2017 and 2016 were as follows: Years Ended December 31, 2018 2017 2016 Percent of revenue from customers accounting for 10% or more of total revenue: Huawei Technologies Co., Ltd 46 % 40 % 50 % Ciena Corporation 24 % 16 % 15 % Percent of revenue from top five customers 87 % 78 % 82 %
Estimated Useful Lives of Property, Plant and Equipment	Depreciation and amortization are computed using the straight-line method over the following estimated useful lives: Buildings 20-30 years Machinery and equipment 2-7 years Furniture, fixtures and office equipment 3-5 years Software 5-7 years Leasehold improvements life of the asset or lease term, if shorter

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Summary of Revenue by Product Group and Geographical Region	Revenue from sale of hardware products is recognized upon transfer of control to the customer. The performance obligation for the sale of hardware products is satisfied at a point in time. The Company has aligned its products in two groups - High Speed Products and Network Products and Solutions. The following presents revenue by product group (in thousands): Years Ended December 31, 2018 2017 2016 High Speed Products $ 275,803 $ 241,780 $ 277,258 Network Products and Solutions 46,737 51,114 134,165 Total revenue $ 322,540 $ 292,894 $ 411,423 The following table presents the Company's revenue information by geographical region. Revenue is classified based on the ship to location requested by the customer. Such classification recognizes that for many customers, including those in North America or in Europe, designated shipping points are often in China or elsewhere in Asia (in thousands): Years Ended December 31, 2018 2017 2016 China $ 187,277 $ 161,637 $ 254,625 Americas 70,906 52,973 76,091 Rest of world 64,357 78,284 80,707 Total revenue $ 322,540 $ 292,894 $ 411,423

Cash, cash equivalents, short_2

Cash, cash equivalents, short-term investments and restricted cash (Tables)	12 Months Ended
	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Schedule Of Cash, Cash Equivalents Short Term Investments And Restricted Cash And Investments	The following table summarizes the Company’s cash, cash equivalents, short-term investments, and restricted cash at December 31, 2018 and 2017 (in thousands): December 31, 2018 December 31, 2017 Cash and cash equivalents: Cash $ 58,185 78,906 Cash equivalents — — Cash and cash equivalents $ 58,185 $ 78,906 Short-term investments $ 7,481 $ 12,311 Restricted cash $ 11,053 $ 2,658 December 31, 2018 December 31, 2017 Cash and cash equivalents $ 58,185 $ 78,906 Restricted cash 11,053 2,658 Total cash, cash equivalents and restricted cash shown in the consolidated statement of cash flows $ 69,238 $ 81,564
Summary of Unrealized Gains and Losses Related to Cash Equivalents and Investments in Marketable Securities	The following table summarizes the Company’s unrealized gains and losses related to the cash equivalents and short-term investments in marketable securities designated as available-for-sale (in thousands): As of December 31, 2018 As of December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Marketable securities: Money market accounts $ — $ — $ — $ — $ — $ — $ — $ — Money market funds 7,481 — — 7,481 11,561 — — 11,561 Corporate debt securities — — — — — — — — U.S. government securities — — — — 751 — (1 ) 750 Sovereign government bonds — — — — — — — — Total $ 7,481 $ — $ — $ 7,481 $ 12,312 $ — $ (1 ) $ 12,311 Reported as: Cash equivalents $ — $ — $ — $ — $ — $ — $ — $ — Short-term investments 7,481 — — 7,481 12,312 — (1 ) 12,311 Total $ 7,481 $ — $ — $ 7,481 $ 12,312 $ — $ (1 ) $ 12,311
Maturities of Marketable Securities	As of December 31, 2018 and 2017, maturities of marketable securities were as follows (in thousands): December 31, 2018 December 31, 2017 Less than 1 year $ 7,481 $ 12,311 Due in 1 to 2 years — — Due in 3 to 5 years — — Total $ 7,481 $ 12,311

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets	The following table presents the Company’s assets that are measured at fair value on a recurring basis (in thousands): December 31, 2018 December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash equivalents and short-term investments: Money market funds $ 7,481 $ — $ — $ 7,481 $ 11,561 $ — $ — $ 11,561 U.S. government securities — — — — 750 — — 750 Money market accounts — — — — — — — — Total $ 7,481 $ — $ — $ 7,481 $ 12,311 $ — $ — $ 12,311 Mutual funds held in Rabbi Trust, recorded in other long-term assets $ 465 $ — $ — $ 465 $ 523 $ — $ — $ 523
Fair Value of Financial Liabilities	The following table presents the Company’s liabilities that are measured at fair value on a recurring basis (in thousands): As of December 31, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Rusnano payment derivative $ — $ — $ 2,000 $ 2,000 $ — $ — $ 389 $ 389 Foreign currency forward contracts — — — — — (43 ) — (43 ) $ — $ — $ 2,000 $ 2,000 $ — $ (43 ) $ 389 $ 346

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Income per Share	The following table sets forth the computation of the basic and diluted net loss per share attributable to NeoPhotonics Corporation common stockholders for the periods indicated (in thousands, except per share amounts): Years Ended December 31, 2018 2017 2016 Numerator: Net loss $ (43,637 ) $ (53,333 ) $ (205 ) Denominator: Weighted average shares used to compute per share amount: Basic 45,144 43,431 41,798 Dilutive effect of equity awards — — — Diluted 45,144 43,431 41,798 Basic net loss per share $ (0.97 ) $ (1.23 ) (0.00) Diluted net loss per share $ (0.97 ) $ (1.23 ) (0.00)
Potentially Dilutive Securities Excluded from Computation of Diluted Net Income per Share Attributable to Common Stockholders	The Company has excluded the impact of the following outstanding employee stock options, restricted stock units, common stock warrants and shares expected to be issued under its employee stock purchase plan from the computation of diluted net loss per share, as their effect would have been antidilutive (in thousands): December 31, 2018 2017 2016 Employee stock options 3,203 3,934 4,301 Restricted stock units 2,486 2,405 2,089 Market-based restricted stock units 695 — — Employee stock purchase plan 414 421 306 6,798 6,760 6,696

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Summary of Purchase Accounting and Tangible and Intangible Assets Acquired and Liabilities Assumed	The following table summarizes the allocation of the assets acquired and liabilities assumed as of the acquisition date and subsequent adjustments (in thousands): Total purchase consideration: Cash paid $ 1,500 Notes payable 15,482 Total $ 16,982 Fair value of assets acquired: Accounts receivable $ 9,274 Inventories 1,693 Prepaid expenses and other current assets 670 Property, plant and equipment 6,917 Intangible assets acquired: Developed technology 4,100 Customer relationships 700 Total $ 23,354 Less: fair value of liabilities assumed: Accounts payable $ (7,427 ) Accrued liabilities (60 ) Total $ (7,487 ) Goodwill $ 1,115
Purchase Price Allocation of Intangible Assets	The following table presents details of the purchase price allocated to the acquired intangible assets at the acquisition date: Useful Life Purchased intangible assets (In years) (In thousands) Developed technology 7 $ 4,100 Customer relationships 2 700 Total purchased intangible assets $ 4,800

Purchased intangible assets (Ta

Purchased intangible assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Purchased Intangible Assets	Purchased intangible assets consist of the following (in thousands): December 31, 2018 December 31, 2017 Gross Assets Accumulated Amortization Net Assets Gross Assets Accumulated Amortization Net Assets Technology and patents $ 37,029 $ (34,995 ) $ 2,034 $ 37,684 $ (34,923 ) $ 2,761 Customer relationships 15,146 (15,026 ) 120 15,425 (14,835 ) 590 Leasehold interest 1,238 (374 ) 864 1,309 (366 ) 943 $ 53,413 $ (50,395 ) $ 3,018 $ 54,418 $ (50,124 ) $ 4,294
Amortization Expense of Purchased Intangible Assets	The following table presents details of the amortization expense of the Company’s purchased intangible assets as reported in the consolidated statements of operations (in thousands): Years ended December 31, 2018 2017 2016 Cost of goods sold $ 756 $ 869 $ 2,871 Operating expenses 475 472 1,609 Total $ 1,231 $ 1,341 $ 4,480
Estimated Future Amortization Expense of Purchased Intangible Assets	The estimated future amortization expense of purchased intangible assets as of December 31, 2018, is as follows (in thousands): 2019 $ 856 2020 737 2021 644 2022 28 2023 28 Thereafter 725 $ 3,018

Balance sheet components (Table

Balance sheet components (Tables)	12 Months Ended
	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Restricted Cash	Restricted cash was as follows (in thousands): December 31, 2018 2017 Restricted in connection with notes payable and short-term borrowing (see Note 12) $ 2,589 $ 537 Restricted in connection with asset purchase agreement (see Note 10) 2,019 2,121 Restricted in connection with a current legal dispute with APAT OE (See Note 10) 5,156 — Restricted in connection with government grants received in advance 1,289 — Total restricted cash $ 11,053 $ 2,658 Reported as: Restricted cash $ 11,053 $ 2,658
Accounts Receivable, Net	Accounts receivable, net were as follows (in thousands): December 31, 2018 2017 Accounts receivable $ 74,343 $ 65,499 Trade notes receivable 672 2,356 Allowance for doubtful accounts (264 ) (626 ) $ 74,751 $ 67,229
Summary of Movement in Allowance for Doubtful Accounts	The table below summarizes the movement in the Company’s allowance for doubtful accounts (in thousands): Balance at December 31, 2015 $ (843 ) Reversal of provision for bad debt 382 Write-offs, net of recoveries 36 Balance at December 31, 2016 (425 ) Provision for bad debt (577 ) Write-offs, net of recoveries 376 Balance at December 31, 2017 (626 ) Reversal of provision for bad debt 428 Write-offs, net of recoveries (66 ) Balance at December 31, 2018 $ (264 )
Inventories, net	Inventories were as follows (in thousands): December 31, 2018 2017 Raw materials $ 27,806 $ 33,400 Work in process 13,044 13,246 Finished goods (1) 11,309 20,655 $ 52,159 $ 67,301 (1) Included in finished goods was $5.6 million and $7.1 million of inventory at customer vendor managed inventory locations at December 31, 2018 and 2017 , respectively.
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets were as follows (in thousands): December 31, 2018 2017 Prepaid taxes and taxes receivable $ 5,461 $ 15,162 Transition services agreement receivable (see Note 10) 11,999 12,817 Deposits and other prepaid expenses 3,020 4,138 Other receivable 6,125 4,118 $ 26,605 $ 36,235
Property, Plant and Equipment, Net	Property, plant and equipment, net were as follows (in thousands): December 31, 2018 2017 Land $ 3,157 $ 3,083 Buildings 23,379 24,102 Machinery and equipment 187,746 189,527 Furniture, fixtures, software and office equipment 10,201 9,948 Leasehold improvements 22,000 26,007 246,483 252,667 Less: Accumulated depreciation (146,393 ) (125,102 ) $ 100,090 $ 127,565
Accrued and Other Current Liabilities	Accrued and other current liabilities were as follows (in thousands): December 31, 2018 2017 Employee-related $ 14,899 $ 12,990 Transition services agreement payables (see Note 10) 11,769 11,222 Asset sale related contingent liabilities (see Note 10) 6,751 7,135 Income and other taxes payable 1,580 542 Deferred revenue, current 1,114 939 Accrued warranty 672 1,334 Rusnano payment derivative 2,000 — Accrued litigation settlement 2,645 — Other accrued expenses 8,858 9,080 $ 50,288 $ 43,242
Accrued Warranty	The table below summarizes the movement in the warranty accrual, which is included in accrued and other current liabilities (in thousands): Years ended December 31, 2018 2017 2016 Beginning balance $ 1,334 $ 678 $ 1,175 Warranty accruals 399 1,263 102 Settlements (1,061 ) (607 ) (599 ) Ending balance $ 672 $ 1,334 $ 678
Other Noncurrent Liabilities	Other noncurrent liabilities were as follows (in thousands): December 31, 2018 2017 Pension and other employee-related $ 4,529 $ 4,675 Deferred rent 3,058 2,908 Deferred revenue — 617 Government grant 2,108 1,095 Rusnano payment derivative — 389 Deferred income tax liabilities — 106 Capital lease obligation 282 — Asset retirement obligations and other 3,522 4,285 $ 13,499 $ 14,075

Restructuring (Tables)

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2018
Restructuring and Related Activities [Abstract]
Schedule of Restructuring Reserve by Type	Employee Severance Facilities Consolidation Asset-Related Others Total Restructuring obligations December 31, 2017 $ — $ 1,580 $ 43 $ — $ 1,623 Charges 637 29 1,021 1,616 3,303 Cash payments (196 ) (840 ) (6 ) (5 ) (1,047 ) Non-cash settlements and other (5 ) — (1,058 ) — (1,063 ) Restructuring obligations December 31, 2018 $ 436 $ 769 $ — $ 1,611 $ 2,816

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Components of Debt, Obligations, Weighted Average Interest Rate and Additional Fair Value Information Relating to Outstanding Debt Instruments	The table below summarizes the carrying amount and weighted average interest rate of the Company’s debt (in thousands, except percentages): December 31, 2018 December 31, 2017 Carrying Amount Interest Rate Carrying Amount Interest Rate Note payable to Shanghai Pudong Development Bank $ — — % $ 17,000 4.10 % Note payable to China CITIC Bank — — % 17,000 4.00 % Notes payable to suppliers 4,795 1,607 Total notes payable and short-term borrowing $ 4,795 $ 35,607 Long-term debt, current and non-current: Borrowing under Wells Fargo Credit Facility $ 35,961 4.41 % $ 30,018 3.29 % Mitsubishi Bank loans 11,094 1.05%-1.45% 16,924 1.05% -1.45% Mitsubishi Bank and Yamanashi Chou Bank loan 6,898 1.10 % — Unaccreted discount and issuance costs within current portion of long-term debt (161 ) (86 ) Unaccreted discount and issuance costs within long-term debt, net of current portion (441 ) (295 ) Total long-term debt, net of unaccreted discount and issuance costs $ 53,351 $ 46,561 Reported as: Current portion of long-term debt $ 2,897 $ 6,005 Long-term debt, net of current portion 50,454 40,556 Total long-term debt, net of unaccreted discount and issuance costs $ 53,351 $ 46,561
Maturities of Long-term Debt	At December 31, 2018, maturities of long-term debt were as follows (in thousands): 2019 $ 3,058 2020 3,058 2021 3,058 2022 39,019 2023 3,058 Thereafter 2,702 $ 53,953

Pension Plans (Tables)

Pension Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Funded Status Plans	The funded status of these plans for the years ended December 31, 2018, 2017 and 2016 was as follows (in thousands): 2018 2017 2016 RAP RAP RAP Change in projected benefit obligation: Projected benefit obligation, beginning of period $ 4,616 $ 4,802 $ 5,086 Service cost — — — Interest cost 4 5 11 Benefits paid (517 ) (411 ) (551 ) Actuarial (gain)/loss 95 32 72 Curtailment/Settlement — — — Transfer from DBCPP to RAP — — — Currency translation adjustment 110 188 184 Projected benefit obligation, end of period $ 4,308 $ 4,616 $ 4,802 Change in plan assets: Plan assets at fair value, beginning of period $ — $ — $ — Employer contributions — — — Benefits paid — — — Transfer to DCP — — — Currency translation adjustment — — — Plan assets at calculated amount, end of period $ — $ — $ — Amounts recognized in consolidated balance sheets: Accrued and other current liabilities $ 257 $ 488 $ 393 Other noncurrent liabilities $ 4,051 $ 4,128 $ 4,409 Amount recognized in accumulated other comprehensive loss: Defined benefit pension plans adjustment $ 373 $ 271 $ 230 Accumulated benefit obligation, end of period $ 4,308 $ 4,616 $ 4,802
Periodic Pension Cost	Net periodic pension cost associated with these plans for the years ended December 31, 2018, 2017 and 2016 included the following components (in thousands): 2018 2017 2016 RAP RAP RAP Service cost $ — $ — $ — Interest cost 4 5 11 Other — — — Curtailment/settlement (gain) loss — — — Net periodic pension costs $ 4 $ 5 $ 11
Estimated Future Benefit Payments Under Plans	Estimated future benefit payments under the RAP are as follows (in thousands): 2019 $ 188 2020 513 2021 626 2022 295 2023 — 2024 - 2026 1,631 Thereafter 1,055 $ 4,308

Commitments and contingencies (

Commitments and contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Commitments Under All Operating Leases	As of December 31, 2018, the future minimum commitments under the Company’s non-cancelable operating leases are as follows (in thousands): Years ending December 31, 2019 $ 3,618 2020 3,113 2021 3,059 2022 3,056 2023 3,049 Thereafter 11,437 $ 27,332

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Schedule of Accumulated Other Comprehensive Income, Net of Related Taxes	The following table shows the components of accumulated other comprehensive income (loss), net of taxes, as of December 31, 2018 and 2017 (in thousands): December 31, 2018 December 31, 2017 Foreign currency translation adjustments $ (6,897 ) $ 567 Unrealized loss on available-for-sale securities — (1 ) Defined benefit pension plan adjustment (229 ) (168 ) $ (7,126 ) $ 398

Stock-based compensation (Table

Stock-based compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Estimated Fair Value of Certain Stock-Based Awards Using Black-Scholes-Merton Valuation Model	The Company estimated the fair value of certain stock-based awards using a Black-Scholes-Merton valuation model with the following assumptions: Years ended December 31, Stock options 2018 2017 2016 Weighted-average expected term (years) 6.02 5.99 5.75 Weighted-average volatility 65% 65% 65% Risk-free interest rate 2.27%-2.62% 2.02%-2.08% 1.01%-1.76% Expected dividends — % — % — % Stock appreciation units Weighted-average expected term (years) 1.94 2.30 2.77 Weighted-average volatility 66% 69% 61% Risk-free interest rate 1.03%-2.81% 0.51%-1.62% 0.45%-1.47% Expected dividends 0 — % — % ESPP Weighted-average expected term (years) 0.72 0.72 0.73 Weighted-average volatility 61% 61% 54% Risk-free interest rate 1.93%-2.59% 0.91%-1.31% 0.39%-0.45% Expected dividends — % — % — %
Summary of Stock Based Compensation Expense	Unamortized stock-based compensation costs capitalized as part of inventory were immaterial in each of the periods presented (in thousands): Years ended December 31, 2018 2017 2016 Cost of goods sold $ 2,596 $ 1,098 $ 3,130 Research and development 3,570 2,491 4,760 Sales and marketing 3,248 1,697 4,105 General and administrative 4,728 2,920 5,081 $ 14,142 $ 8,206 $ 17,076
Summary of Stock Option and Restricted Stock Unit Activity	The following table summarizes the Company’s stock option and restricted stock unit, or RSU, activity during the year ended December 31, 2018: Stock Options Restricted Stock Units Shares Available for Grant Number of Shares Weighted Average Exercise Price Number of Units Weighted Average Grant Date Fair Value Balance at December 31, 2017 959,136 3,933,529 $ 5.55 2,404,637 $ 9.02 Authorized for issuance 1,947,667 — — — — Granted (2,300,056 ) 158,116 6.64 1,446,940 6.83 Exercised/Converted — (778,811 ) 4.39 (1,123,893 ) 8.82 Cancelled/Forfeited 495,576 (110,089 ) 10.07 (241,656 ) 8.74 Balance at December 31, 2018 1,102,323 3,202,745 $ 5.73 2,486,028 $ 7.87
Summary of Information about Stock Options Outstanding	The following table summarizes information about stock options outstanding as of December 31, 2018: Options Outstanding Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in Thousands) Vested and expected to vest 3,152,837 $ 5.70 5.31 $ 4,936,208 Exercisable 2,701,433 $ 5.32 4.78 $ 4,864,959
Summary of Information about Restricted Stock Units Outstanding	The following table summarizes information about RSUs outstanding as of December 31, 2018: Restricted Stock Units Outstanding Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in Thousands) Vested and expected to vest 2,166,565 $ — 1.26 $ 14,039,340
Stock Options - Schedule of Share-based Payment Award, Equity Instruments Other Than Options, Valuation Assumptions	The fair value of market-based RSUs was measured on the grant date using Monte Carlo simulation model with the following assumptions: Years ended December 31, 2018 2017 Weighted-average volatility 66% —% Risk-free interest rate 2.79% —% Expected dividends —% —%
Summary of Stock Appreciation Unit Activity	The following table summarizes the Company’s stock appreciation unit activity during the year ended December 31, 2018: Stock Appreciation Units Weighted-Average Exercise Price Stock appreciation units outstanding as of December 31, 2017 239,824 $ 4.95 Stock appreciation units exercised (31,272 ) $ 4.32 Stock appreciation units cancelled (15,680 ) $ 6.72 Stock appreciation units outstanding as of December 31, 2018 192,872 $ 4.91

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income (Loss) before Income Taxes	The provision for income taxes is based upon the income (loss) before income taxes as follows (in thousands): Years Ended December 31, 2018 2017 2016 U.S. operations $ (43,384 ) $ (52,725 ) $ (10,217 ) Non-U.S. operations 1,076 301 13,609 $ (42,308 ) $ (52,424 ) $ 3,392
Components of Provision for Income Taxes	The components of the provision for income taxes consisted of the following (in thousands): Years Ended December 31, 2018 2017 2016 Current Federal $ (49 ) $ (144 ) $ (127 ) State 36 3 (13 ) Foreign (1,634 ) 363 (3,925 ) (1,647 ) 222 (4,065 ) Deferred Federal 42 4 (24 ) State — — — Foreign 276 (1,135 ) 492 Total provision $ (1,329 ) $ (909 ) $ (3,597 )
Difference in Provision for Income Taxes from Amount Obtained by Applying U.S. Federal Statutory Rate	The provision for income taxes differs from the amount obtained by applying the U.S. federal statutory tax rate as follows (in thousands, except percentages): Years Ended December 31, 2018 2017 2016 Federal statutory rate 21 % 35 % 35 % Tax at federal statutory rate $ 8,869 $ 18,354 $ (1,185 ) State taxes, net of federal benefit 36 2 (8 ) Mandatory repatriation/Section 956 — (5,718 ) (19 ) Nondeductible expenses (371 ) (67 ) (727 ) Stock-based compensation (1,079 ) (314 ) (877 ) Change in valuation allowance (10,094 ) 16,273 (1,455 ) Research and development 914 851 1,175 Foreign rate differences (697 ) (2,819 ) (1,215 ) Foreign tax credit 49 144 127 Change in prior year deferred balances 1,653 (28,262 ) 920 Other (609 ) 647 (333 ) Total provision for income taxes from continuing operations $ (1,329 ) $ (909 ) $ (3,597 )
Components of Deferred Income Tax Assets and Liabilities	Deferred income tax assets and liabilities comprise the following (in thousands): December 31, 2018 2017 Deferred Tax Assets: Net operating loss carryforwards $ 56,828 $ 44,912 Federal and state credits 28,328 26,170 Reserves, accruals and other 11,265 9,698 Fixed assets and intangibles 2,398 1,259 Total deferred tax assets 98,819 82,039 Valuation allowance (92,891 ) (76,101 ) Total deferred tax assets, net of valuation allowance 5,928 5,938 Less deferred tax liabilities: Acquired intangibles (313 ) (2,054 ) Property, plant and equipment (4,754 ) (3,338 ) Net deferred tax assets $ 861 $ 546 Reported as: Long term deferred tax assets, included within other long-term assets $ 861 $ 652 Long term deferred income tax liabilities, included within noncurrent liabilities — (106 ) Net deferred tax assets $ 861 $ 546
Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Balance at December 31, 2015 $ 20,686 Gross increases for tax positions of current year 2,920 Balance at December 31, 2016 23,606 Gross increases for tax positions of current year 1,933 Balance at December 31, 2017 25,539 Gross increases for tax positions of current year 657 Balance at December 31, 2018 $ 26,196

Segment and geographic inform_2

Segment and geographic information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Revenue and Long-Lived Assets By Geographical Region	Through 2018, the Company has aligned its products to High Speed Products and Network Products and Solutions (see Note 3). The following tables set forth the Company’s asset information by geographic region (in thousands): As of December 31, 2018 2017 Property, plant and equipment, net: China $ 27,329 $ 37,212 United States 29,054 42,243 Japan 29,631 43,826 Rest of world 14,076 4,284 Total $ 100,090 $ 127,565

Selected Quarterly Financial _2

Selected Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Summary of Quarterly Financial Information	The following tables set forth a summary of the Company’s quarterly financial information for each of the four quarters for the years ended December 31, 2018 and 2017: Year ended December 31, 2018 First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share data) Revenues $ 68,586 $ 81,102 $ 81,748 $ 91,104 Gross profit 9,182 15,472 18,933 22,586 Net loss (18,246 ) (10,537 ) (8,125 ) (6,729 ) Basic net loss per share $ (0.41 ) $ (0.24 ) $ (0.18 ) $ (0.15 ) Diluted net loss per share $ (0.41 ) $ (0.24 ) $ (0.18 ) $ (0.15 ) Weighted averages shares used to compute basic net loss per share 44,259 44,665 45,476 46,150 Weighted averages shares used to compute diluted net loss per share 44,259 44,665 45,476 46,150 Year ended December 31, 2017 First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share data) Revenues $ 71,688 $ 73,214 $ 71,121 $ 76,871 Gross profit 18,503 16,777 10,513 15,686 Net loss (11,522 ) (9,341 ) (18,187 ) (14,283 ) Basic net loss per share $ (0.27 ) $ (0.22 ) $ (0.42 ) $ (0.32 ) Diluted net loss per share (0.27 ) (0.22 ) (0.42 ) (0.32 ) Weighted averages shares used to compute basic net loss per share 42,615 43,219 43,790 44,079 Weighted averages shares used to compute diluted net loss per share 42,615 43,219 43,790 44,079

The Company and basis of pres_2

The Company and basis of presentation - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Concentration Risk [Line Items]
Working capital	$ 116,800,000
Cash, cash equivalents, short-term investments and restricted cash	76,700,000
Operating losses	41,658,000	$ 51,364,000	$ (3,019,000)
Cash outflows from operating activities	(19,595,000)	32,767,000	$ (53,836,000)
Accumulated deficit	397,472,000	352,011,000
Notes payable	4,800,000
Current portion of long-term debt	2,897,000	$ 6,005,000
Revolving Credit Facility | Wells Fargo Bank, National Association
Concentration Risk [Line Items]
Line of credit maximum borrowing capacity				$ 50,000,000
Amount outstanding on line of credit	36,000,000
Line of credit remaining borrowing capacity	14,000,000
Required amount to be maintained as unused borrowing capacity	$ 5,000,000

Summary of significant accoun_4

Summary of significant accounting policies - Concentration of risk (Details) - Customer Concentration Risk - Revenue from Contract with Customer	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Huawei Technologies Co., Ltd
Concentration Risk [Line Items]
Percentage of concentration of credit risk	46.00%	40.00%	50.00%
Ciena Corporation
Concentration Risk [Line Items]
Percentage of concentration of credit risk	24.00%	16.00%	15.00%
Top Five Customers
Concentration Risk [Line Items]
Percentage of concentration of credit risk	87.00%	78.00%	82.00%

Summary of significant accoun_5

Summary of significant accounting policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jan. 01, 2018USD ($)
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 11,053,000	$ 2,658,000
Goodwill impairment charges	0	0
Asset impairment charges	1,000,000	400,000	$ 0
Loss on foreign currency contracts	2,200,000
Gain on foreign currency contracts		2,100,000
Net gains (losses) resulting from foreign exchange transactions	1,400,000	$ (500,000)	$ (100,000)
Effective income tax rate reconciliation, share-based compensation, excess tax benefit, amount	$ 8,600,000
Conversion of Stock, Shares Issued	1
Cumulative effect of new accounting standard				$ (1,824,000)
Land use rights
Summary Of Significant Accounting Policies [Line Items]
Useful Life	45 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful Life	2 years
Product warranty period	1 year
Maximum
Summary Of Significant Accounting Policies [Line Items]
Useful Life	7 years
Product warranty period	3 years
Notes Receivable
Summary Of Significant Accounting Policies [Line Items]
Receivable due period, general	9 months
Customer Concentration Risk | Customer One | Accounts Receivable
Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration of credit risk	35.00%	36.00%
Customer Concentration Risk | Customer Two | Accounts Receivable
Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration of credit risk	17.00%	14.00%
Customer Concentration Risk | Customer Three | Accounts Receivable
Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration of credit risk		10.00%
Accounting Standards Update 2016-09
Summary Of Significant Accounting Policies [Line Items]
Effective income tax rate reconciliation, share-based compensation, excess tax benefit, amount		$ 8,600,000
Accounting Standards Update 2016-16
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of new accounting standard				$ 1,800,000

Summary of significant accoun_6

Summary of significant accounting policies - Estimated Useful Lives of Property, Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2018
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives (in years)	20 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives (in years)	30 years
Machinery and equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives (in years)	2 years
Machinery and equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives (in years)	7 years
Furniture, fixtures, software and office equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives (in years)	3 years
Furniture, fixtures, software and office equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives (in years)	5 years
Software | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives (in years)	5 years
Software | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives (in years)	7 years

Revenue - Revenue by Product Gr

Revenue - Revenue by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total revenue	$ 91,104	$ 81,748	$ 81,102	$ 68,586	$ 76,871	$ 71,121	$ 73,214	$ 71,688	$ 322,540	$ 292,894	$ 411,423
High Speed Products
Disaggregation of Revenue [Line Items]
Total revenue									275,803	241,780	277,258
Network Products and Solutions
Disaggregation of Revenue [Line Items]
Total revenue									$ 46,737	$ 51,114	$ 134,165

Revenue - Revenue From External

Revenue - Revenue From External Customers By Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total revenue	$ 91,104	$ 81,748	$ 81,102	$ 68,586	$ 76,871	$ 71,121	$ 73,214	$ 71,688	$ 322,540	$ 292,894	$ 411,423
China
Disaggregation of Revenue [Line Items]
Total revenue									187,277	161,637	254,625
Americas
Disaggregation of Revenue [Line Items]
Total revenue									70,906	52,973	76,091
Rest of world
Disaggregation of Revenue [Line Items]
Total revenue									$ 64,357	$ 78,284	$ 80,707

Revenue - Narrative (Details)

Revenue - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Contract with customer, liability, revenue recognized	$ 0.9	$ 1.1
Increase (decrease) in deferred revenue		$ 1.6

Cash, cash equivalents, short_3

Cash, cash equivalents, short-term investments and restricted cash - Short term investments and restricted cash and investments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and cash equivalents:
Cash	$ 58,185	$ 78,906
Cash equivalents	0	0
Cash and cash equivalents	58,185	78,906
Short-term investments	7,481	12,311
Cash and cash equivalents	58,185	78,906
Restricted cash	11,053	2,658
Total cash, cash equivalents and restricted cash shown in the consolidated statement of cash flows	$ 69,238	$ 81,564	$ 86,585	$ 78,748

Cash, cash equivalents, short_4

Cash, cash equivalents, short-term investments and restricted cash - Unrealized Gains and Losses Related to Cash Equivalents and Investments in Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 7,481	$ 12,312
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	(1)
Fair Value	7,481	12,311
Money market accounts
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	0	0
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,481	11,561
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	7,481	11,561
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	0	0
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	751
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	(1)
Fair Value	0	750
Sovereign government bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	0	0
Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	0	0
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,481	12,312
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	(1)
Fair Value	$ 7,481	$ 12,311

Cash, cash equivalents, short_5

Cash, cash equivalents, short-term investments and restricted cash - Maturities of marketable securities and additional information (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Less than 1 year	$ 7,481	$ 12,311
Due in 1 to 2 years	0	0
Due in 3 to 5 years	0	0
Total	$ 7,481	$ 12,311

Cash, cash equivalents, short_6

Cash, cash equivalents, short-term investments and restricted cash Cash, cash equivalents, short-term investments and restricted cash - Narrative (Details)	12 Months Ended
	Dec. 31, 2018USD ($)investment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Cash and Cash Equivalents [Abstract]
Impairment losses on its marketable securities | $	$ 0	$ 0	$ 0
Investments in marketable securities in unrealized loss position in excess of 12 months item | investment	0

Fair value measurements - Asset

Fair value measurements - Assets and liabilities measured at fair value on recurring basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	$ 7,481	$ 12,311
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	7,481	12,311
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	7,481	11,561
Money market funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	7,481	11,561
Money market funds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Money market funds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	750
U.S. government securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	750
U.S. government securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
U.S. government securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Money market accounts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Money market accounts | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Money market accounts | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Money market accounts | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Mutual funds held in Rabbi Trust, recorded in other long-term assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	465	523
Mutual funds held in Rabbi Trust, recorded in other long-term assets | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	465	523
Mutual funds held in Rabbi Trust, recorded in other long-term assets | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Mutual funds held in Rabbi Trust, recorded in other long-term assets | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Fair Value, Measurements, Recurring | Rusnano payment derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	2,000	389
Fair Value, Measurements, Recurring | Rusnano payment derivative | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Fair Value, Measurements, Recurring | Rusnano payment derivative | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Fair Value, Measurements, Recurring | Rusnano payment derivative | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	2,000	389
Fair Value, Measurements, Recurring | Foreign currency forward contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	(43)
Fair Value, Measurements, Recurring | Foreign currency forward contracts | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Fair Value, Measurements, Recurring | Foreign currency forward contracts | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	(43)
Fair Value, Measurements, Recurring | Foreign currency forward contracts | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Fair Value, Measurements, Recurring | Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	2,000	346
Fair Value, Measurements, Recurring | Derivative | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	0
Fair Value, Measurements, Recurring | Derivative | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	0	(43)
Fair Value, Measurements, Recurring | Derivative | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	$ 2,000	$ 389

Fair value measurements - Narra

Fair value measurements - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Disposal group, including discontinued operation, assets, current	$ 2,971	$ 0
Fair Value, Measurements, Nonrecurring | Property, plant and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset impairment charges	1,000
Property, plant and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Disposal group, including discontinued operation, assets, current	$ 2,500

Net loss per share - Computatio

Net loss per share - Computation of Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net loss	$ (6,729)	$ (8,125)	$ (10,537)	$ (18,246)	$ (14,283)	$ (18,187)	$ (9,341)	$ (11,522)	$ (43,637)	$ (53,333)	$ (205)
Denominator:
Weighted average shares used to compute per share amount, basic (in shares)	46,150	45,476	44,665	44,259	44,079	43,790	43,219	42,615	45,144	43,431	41,798
Dilutive effect of equity awards (in shares)									0	0	0
Weighted average shares used to compute diluted net (loss) income (in shares)	46,150	45,476	44,665	44,259	44,079	43,790	43,219	42,615	45,144	43,431	41,798
Basic net loss per share (USD per share)	$ (0.15)	$ (0.18)	$ (0.24)	$ (0.41)	$ (0.32)	$ (0.42)	$ (0.22)	$ (0.27)	$ (0.97)	$ (1.23)	$ 0
Diluted net loss per share (USD per share)	$ (0.15)	$ (0.18)	$ (0.24)	$ (0.41)	$ (0.32)	$ (0.42)	$ (0.22)	$ (0.27)	$ (0.97)	$ (1.23)	$ 0

Net loss per share - Potentiall

Net loss per share - Potentially Dilutive Securities Excluded From Computation of Diluted Net Loss per Share Attributable to Common Stockholders (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	6,798	6,760	6,696
Employee stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	3,203	3,934	4,301
Restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	2,486	2,405	2,089
Market-based restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	695	0	0
Employee stock purchase plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	414	421	306

Business Combinations (Details)

Business Combinations (Details) - USD ($) $ in Thousands	Apr. 16, 2015	Jan. 02, 2015	Nov. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Acquisition and asset sale related costs				$ 427	$ 130	$ 2,125
Tunable Laser Product Lines From EMCORE Corporation
Business Acquisition [Line Items]
Purchase price	$ 16,982	$ 17,500
Cash consideration paid	1,500	1,500
Issuance of notes to the seller of acquired business	$ 15,482	$ 16,000
Acquisition and asset sale related costs							$ 900
EigenLight Corporation
Business Acquisition [Line Items]
Cash consideration paid			$ 400

Business Combinations - Allocat

Business Combinations - Allocation of Assets acquired, liabilities assumed and Purchase price (Details) - USD ($) $ in Thousands	Apr. 16, 2015	Jan. 02, 2015	Dec. 31, 2018	Dec. 31, 2017
Liabilities assumed:
Goodwill			$ 1,115	$ 1,115
Tunable Laser Product Lines From EMCORE Corporation
Total purchase consideration:
Cash paid	$ 1,500	$ 1,500
Notes payable	15,482	16,000
Total	16,982	17,500
Fair value of assets acquired:
Accounts receivable	9,274
Inventories	1,693
Prepaid expenses and other current assets	670
Property, plant and equipment	6,917
Intangible assets acquired:
Purchased intangible assets		4,800
Total	23,354
Liabilities assumed:
Accounts payable	(7,427)
Accrued liabilities	(60)
Total	(7,487)
Goodwill	1,115
Tunable Laser Product Lines From EMCORE Corporation | Developed technology
Intangible assets acquired:
Purchased intangible assets	4,100	4,100
Tunable Laser Product Lines From EMCORE Corporation | Customer relationships
Intangible assets acquired:
Purchased intangible assets	$ 700	$ 700

Business Combinations - Summary

Business Combinations - Summary of Intangible Assets Acquired (Details) - Tunable Laser Product Lines From EMCORE Corporation - USD ($) $ in Thousands	Jan. 02, 2015	Apr. 16, 2015
Business Acquisition [Line Items]
Purchased intangible assets	$ 4,800
Developed technology
Business Acquisition [Line Items]
Useful Life	7 years
Purchased intangible assets	$ 4,100	$ 4,100
Customer relationships
Business Acquisition [Line Items]
Useful Life	2 years
Purchased intangible assets	$ 700	$ 700

Purchased intangible assets - C

Purchased intangible assets - Components (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Assets	$ 53,413	$ 54,418
Accumulated Amortization	(50,395)	(50,124)
Net Assets	3,018	4,294
Technology and patents
Finite-Lived Intangible Assets [Line Items]
Gross Assets	37,029	37,684
Accumulated Amortization	(34,995)	(34,923)
Net Assets	2,034	2,761
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Assets	15,146	15,425
Accumulated Amortization	(15,026)	(14,835)
Net Assets	120	590
Leasehold interest
Finite-Lived Intangible Assets [Line Items]
Gross Assets	1,238	1,309
Accumulated Amortization	(374)	(366)
Net Assets	$ 864	$ 943

Purchased intangible assets - A

Purchased intangible assets - Amortization expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Cost of goods sold	$ 756	$ 869	$ 2,871
Operating expenses	475	472	1,609
Total	$ 1,231	$ 1,341	$ 4,480

Purchased intangible assets - E

Purchased intangible assets - Estimated future amortization expense (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
2,019	$ 856
2,020	737
2,021	644
2,022	28
2,023	28
Thereafter	725
Net Assets	$ 3,018	$ 4,294

Balance sheet components - Rest

Balance sheet components - Restricted Cash and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	$ 11,053	$ 2,658
Restricted cash	11,053	2,658
Restricted in connection with asset purchase agreement
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	2,019	2,121
Restricted in connection with notes payable and short-term borrowing
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	2,589	537
APAT OE Legal Dispute
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	5,156
APAT OE Legal Dispute | APAT OE Legal Dispute
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments		0
Advances, Government Grants Received
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	$ 1,289	$ 0

Balance sheet components - Acco

Balance sheet components - Accounts receivable, net (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Accounts receivable	$ 74,343	$ 65,499
Trade notes receivable	672	2,356
Allowance for doubtful accounts	(264)	(626)
Accounts receivable, Net ,Total	$ 74,751	$ 67,229

Balance sheet components - Allo

Balance sheet components - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reversal of provision for bad debt	$ (61)	$ (577)	$ 382
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	(626)	(425)	(843)
Reversal of provision for bad debt	428	(577)	382
Write-offs, net of recoveries	(66)	376	36
Ending Balance	$ (264)	$ (626)	$ (425)

Balance sheet components - Inve

Balance sheet components - Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Raw materials	$ 27,806	$ 33,400
Work in process	13,044	13,246
Finished goods	11,309	20,655
Inventories	52,159	67,301
Finished goods, at vendor managed inventory locations	$ 5,600	$ 7,100

Balance sheet components - Asse

Balance sheet components - Assets held for sale (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Long Lived Assets Held-for-sale [Line Items]
Restructuring charges		$ 3,135	$ 3,934	$ 0
Disposal group, including discontinued operation, assets, current	$ 2,971	2,971	$ 0
NeoPhotonics Corporation | Joint Stock Company Rusnano
Long Lived Assets Held-for-sale [Line Items]
Assets held for sale, percentage to be acquired	100.00%
Rusnano Group
Long Lived Assets Held-for-sale [Line Items]
Restructuring charges		1,600
Property, plant and equipment
Long Lived Assets Held-for-sale [Line Items]
Disposal group, including discontinued operation, assets, current	$ 2,500	2,500
Prepaid Expenses and Other Current Assets
Long Lived Assets Held-for-sale [Line Items]
Disposal group, including discontinued operation, assets, current	$ 500	$ 500

Balance sheet components - Prep

Balance sheet components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Prepaid taxes and taxes receivable	$ 5,461	$ 15,162
Transition services agreement receivable (see Note 10)	11,999	12,817
Deposits and other prepaid expenses	3,020	4,138
Other receivable	6,125	4,118
Prepaid expenses and other current assets	$ 26,605	$ 36,235

Balance sheet components - Prop

Balance sheet components - Property, Plant and Equipment, net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 246,483,000	$ 252,667,000
Less: Accumulated depreciation	(146,393,000)	(125,102,000)
Property, plant and equipment, net	100,090,000	127,565,000
Depreciation expense	29,900,000	27,000,000	$ 17,900,000
Asset impairment charges	1,000,000	400,000	0
Purchases of property, plant and equipment, unpaid	1,500,000	10,000,000	$ 16,100,000
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment	3,157,000	3,083,000
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment	23,379,000	24,102,000
Asset impairment charges		100,000
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	187,746,000	189,527,000
Furniture, fixtures, software and office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	10,201,000	9,948,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 22,000,000	$ 26,007,000

Balance sheet components - Accr

Balance sheet components - Accrued and other current liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Employee-related	$ 14,899	$ 12,990
Transition services agreement payables (see Note 10)	11,769	11,222
Asset sale related contingent liabilities (see Note 10)	6,751	7,135
Income and other taxes payable	1,580	542
Deferred revenue, current	1,114	939
Accrued warranty	672	1,334
Rusnano payment derivative	2,000	0
Accrued litigation settlement	2,645	0
Other accrued expenses	8,858	9,080
Accrued and other current liabilities	$ 50,288	$ 43,242

Balance sheet components - Ac_2

Balance sheet components - Accrued warranty (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]
Beginning balance	$ 1,334	$ 678	$ 1,175
Warranty accruals	399	1,263	102
Settlements	(1,061)	(607)	(599)
Ending balance	$ 672	$ 1,334	$ 678

Balance sheet components - Othe

Balance sheet components - Other noncurrent liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Pension and other employee-related	$ 4,529	$ 4,675
Deferred rent	3,058	2,908
Deferred revenue	0	617
Government grant	2,108	1,095
Rusnano payment derivative	0	389
Deferred income tax liabilities	0	106
Capital lease obligation	282	0
Asset retirement obligations and other	3,522	4,285
Other noncurrent liabilities	$ 13,499	$ 14,075

Asset sale (Details)

Asset sale (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition services agreement receivable (Note 5)		$ 11,999	$ 12,817
Transition services agreement payables (Note 5)		11,769	11,222
Assets held for sale		2,971	0
Gain within operating income		(200)	$ 2,193	$ 0
Other current liabilities | Indemnification agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent liability		$ 6,800
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale				13,900
Reclassification from assets held-for-sale	$ 3,400
Assets sold	12,800
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Inventories
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, other				13,100
Assets sold	12,100
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Property, plant and equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, other				$ 800
Assets sold	700
APAT OE | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration received pursuant to asset purchase agreement	25,000
Proceeds from post-closing transaction services fees under transition services agreement	1,400
Disposal group consideration adjustment	21,600
Consideration adjustment for potential indemnification claims	$ 10,000

Restructuring (Details)

Restructuring (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 3,303
Write-down of inventories	6,133	$ 8,349	$ 2,983
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2017	1,623
Charges	3,303
Cash payments	(1,047)
Non-cash settlements and other	(1,063)
Restructuring obligations December 31, 2018	2,816	1,623
Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	637
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2017	0
Charges	637
Cash payments	(196)
Non-cash settlements and other	(5)
Restructuring obligations December 31, 2018	436	0
Facilities Consolidation
Restructuring Cost and Reserve [Line Items]
Restructuring charges	29
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2017	1,580
Charges	29
Cash payments	(840)
Non-cash settlements and other	0
Restructuring obligations December 31, 2018	769	1,580
Asset-Related
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,021
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2017	43
Charges	1,021
Cash payments	(6)
Non-cash settlements and other	(1,058)
Restructuring obligations December 31, 2018	0	43
Others
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,616
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2017	0
Charges	1,616
Cash payments	(5)
Non-cash settlements and other	0
Restructuring obligations December 31, 2018	1,611	0
Cost of goods sold
Restructuring Cost and Reserve [Line Items]
Restructuring charges	200	800
Write-down of inventories		2,000
Restructuring Reserve [Roll Forward]
Charges	200	800
Operating Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3,100	3,900
Restructuring Reserve [Roll Forward]
Charges	$ 3,100	$ 3,900

Debt - Components of Debt, Obli

Debt - Components of Debt, Obligations, Weighted Average Interest Rate (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total notes payable and short-term borrowing	$ 4,795	$ 35,607
Total long-term debt, net of unaccreted discount and issuance costs	53,351	46,561
Current portion of long-term debt	2,897	6,005
Long-term debt, net of current portion	50,454	40,556
Mitsubishi Bank
Debt Instrument [Line Items]
Long-term debt, gross	11,094	16,924
Long Term Debt Current
Debt Instrument [Line Items]
Unaccreted discount and issuance costs within current portion of long-term debt	(161)	(86)
Long Term Debt Non Current
Debt Instrument [Line Items]
Unaccreted discount and issuance costs within long-term debt, net of current portion	(441)	(295)
Wells Fargo Credit Facility | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross	$ 35,961	$ 30,018
Interest Rate	4.41%	3.29%
Mitsubishi Bank Loans And Yamanashi Chou Bank Loans | Notes Payable to Banks
Debt Instrument [Line Items]
Long-term debt, gross	$ 6,898
Interest Rate	1.10%
Notes Payable to Banks | Note payable to Shanghai Pudong Development Bank
Debt Instrument [Line Items]
Total notes payable and short-term borrowing	$ 0	$ 17,000
Interest Rate	0.00%	4.10%
Notes Payable to Banks | Note payable to China CITIC Bank
Debt Instrument [Line Items]
Total notes payable and short-term borrowing	$ 0	$ 17,000
Interest Rate	0.00%	4.00%
Notes Payable
Debt Instrument [Line Items]
Total notes payable and short-term borrowing	$ 4,795	$ 1,607
Minimum | Mitsubishi Bank
Debt Instrument [Line Items]
Interest Rate	1.05%	1.05%
Maximum | Mitsubishi Bank
Debt Instrument [Line Items]
Interest Rate	1.45%	1.45%

Debt - Narrative (Details)

Debt - Narrative (Details)

Feb. 25, 2015JPY (¥)

Jan. 31, 2019USD ($)

Aug. 31, 2018USD ($)

Feb. 28, 2018USD ($)

Jan. 31, 2018USD ($)

Jan. 31, 2018JPY (¥)

Dec. 31, 2017USD ($)

Nov. 30, 2017USD ($)

Sep. 30, 2017USD ($)

Jul. 31, 2017USD ($)

Mar. 31, 2017USD ($)

Dec. 31, 2018USD ($)debt_instrument

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)letter_of_credit

Dec. 31, 2018CNY (¥)

Dec. 31, 2018JPY (¥)

Jan. 31, 2018JPY (¥)

Dec. 31, 2017CNY (¥)

Jun. 30, 2017USD ($)

Mar. 31, 2017JPY (¥)

Feb. 25, 2015USD ($)

Feb. 25, 2015JPY (¥)

Debt Instrument [Line Items]

Number of letters of credit issued | letter_of_credit

3

Repayment of notes payable

$ 3,732,000

$ 11,639,000

$ 18,007,000

Comerica | Revolving Credit Facility

Debt Instrument [Line Items]

Current borrowing capacity

$ 30,000,000

Mitsubishi Bank

Debt Instrument [Line Items]

Short-term line of credit facility | ¥

¥ 616,800,000

Senior Secured Revolving Credit Facility, expires April 2017 | Federal Funds Effective Rate | Comerica

Debt Instrument [Line Items]

Debt instrument, basis spread

1.00%

Senior Secured Revolving Credit Facility, expires April 2017 | Daily Adjusting LIBOR Rate | Comerica

Debt Instrument [Line Items]

Debt instrument, basis spread

1.00%

Senior Secured Revolving Credit Facility, expires April 2017 | Libor Plus Rate | Comerica

Debt Instrument [Line Items]

Debt instrument, basis spread

2.75%

Senior Secured Revolving Credit Facility, expires April 2017 | Credit Facility Base Rate | Comerica

Debt Instrument [Line Items]

Debt instrument, basis spread

1.75%

Wells Fargo Credit Facility | Line of Credit

Debt Instrument [Line Items]

Line of credit maximum borrowing capacity

$ 50,000,000

Short-term line of credit facility

$ 30,000,000

Outstanding balance of line of credit facilities

$ 36,000,000

Cash balance available for borrowing

100.00%

Cash balance max borrowing

$ 15,000,000

Line of credit facility, increase (decrease)

25,000,000

Repayment of notes payable

$ 20,000,000

Line of credit facility, collateral

20

Unused borrowing capacity

$ 5,000,000

Interest rate

3.29%

4.41%

3.29%

4.41%

4.41%

3.29%

Line of credit remaining borrowing capacity

$ 14,000,000

Required amount to be maintained as unused borrowing capacity

5,000,000

Wells Fargo Credit Facility | Prime Rate | Line of Credit

Debt Instrument [Line Items]

Commitment fee

0.25%

Term Loan A | Mitsubishi Bank

Debt Instrument [Line Items]

Debt, aggregate principal amount

$ 4,400,000

¥ 500,000,000

Term Loan A | Tokyo Interbank Offered Rate (TIBOR) | Mitsubishi Bank

Debt Instrument [Line Items]

Debt instrument, basis spread

1.40%

Term Loan B | Mitsubishi Bank

Debt Instrument [Line Items]

Debt, aggregate principal amount

9,100,000

1,000,000,000

Debt, periodic principal payments | ¥

¥ 8,333,000

Debt, lump sum payment on the maturity date | ¥

¥ 8,373,000

Debt issuance costs

$ 400,000

¥ 40,500,000

Term Loan B | Tokyo Interbank Offered Rate (TIBOR) | Mitsubishi Bank

Debt Instrument [Line Items]

Debt instrument, basis spread

1.40%

Mitsubishi Bank Term Loan A | Notes Payable to Banks

Debt Instrument [Line Items]

Short-term line of credit facility

5,600,000

Repayments of lines of credit

$ 4,400,000

¥ 500,000,000

Mitsubishi Bank Loans | Notes Payable to Banks

Debt Instrument [Line Items]

Unamortized debt issuance costs

600,000

¥ 66,200,000

Mitsubishi Bank Loan 2017 | Notes Payable to Banks

Debt Instrument [Line Items]

Short-term line of credit facility

$ 6,300,000

¥ 690,000,000

Debt, aggregate principal amount

$ 6,300,000

¥ 690,000,000

Debt instrument term

72 months

72 months

Mitsubishi Bank Loan 2017 | Tokyo Interbank Offered Rate (TIBOR) | Notes Payable to Banks

Debt Instrument [Line Items]

Debt instrument, basis spread

1.00%

Term Loan C | Mitsubishi Bank and The Tamanashi Chou Ban, Ltd.

Debt Instrument [Line Items]

Line of credit maximum borrowing capacity

$ 7,700,000

¥ 850,000,000

Debt instrument term

82 months

82 months

Term Loan C | Tokyo Interbank Offered Rate (TIBOR) | Mitsubishi Bank and The Tamanashi Chou Ban, Ltd.

Debt Instrument [Line Items]

Debt instrument, basis spread

1.00%

1.00%

Notes Payable | Second Line Of Credit, Expires July 2019 | Subsidiary in China

Debt Instrument [Line Items]

Short-term line of credit facility

4,400,000

¥ 30,000,000

Bankers Acceptance

Debt Instrument [Line Items]

Restricted cash and investments, current

$ 500,000

$ 2,600,000

$ 500,000

Bankers Acceptance | Subsidiary in China

Debt Instrument [Line Items]

Outstanding balance of line of credit facilities

$ 1,600,000

$ 1,600,000

Bankers Acceptance | Second Line Of Credit, Expires July 2019 | Subsidiary in China

Debt Instrument [Line Items]

Percentage of compensating balance requirement for bank acceptance drafts

50.00%

Short-term line of credit facility

$ 8,700,000

¥ 60,000,000

Bankers Acceptance | First Credit Facility Expires July 2019

Debt Instrument [Line Items]

Percentage of compensating balance requirement for bank acceptance drafts

30.00%

Line of Credit | Amended Comerica Bank Credit Facility

Debt Instrument [Line Items]

Current borrowing capacity

$ 17,000,000

Line of credit facility, maximum indebtedness under debt covenant

$ 20,000,000

Notes Payable to Banks | Note payable to China CITIC Bank

Debt Instrument [Line Items]

Borrowing on line of credit

$ 17,000,000

$ 17,000,000

Debt instrument, basis spread

2.55%

Stated interest rate

4.70%

Repayments of lines of credit

$ 17,000,000

Interest rate

4.00%

0.00%

4.00%

0.00%

0.00%

4.00%

China | CITIC Bank | Bank Acceptance Drafts

Debt Instrument [Line Items]

Line of credit maximum borrowing capacity

$ 56,800,000

$ 56,800,000

¥ 390,600,000

Percentage of compensating balance requirement for bank acceptance drafts

36.00%

China | CITIC Bank | Line of Credit

Debt Instrument [Line Items]

Line of credit maximum borrowing capacity

$ 36,400,000

$ 36,400,000

¥ 250,000,000

China | First Credit Facility Expires June 2016

Debt Instrument [Line Items]

Percentage of compensating balance requirement for bank acceptance drafts

50.00%

China | Notes Payable

Debt Instrument [Line Items]

Number of credit facilities | debt_instrument

2

China | Notes Payable | First Credit Facility Expires June 2016

Debt Instrument [Line Items]

Short-term line of credit facility

$ 17,400,000

¥ 120,000,000

Borrowing on line of credit

$ 17,000,000

China | Bankers Acceptance

Debt Instrument [Line Items]

Outstanding balance of line of credit facilities

4,800,000

China | Bankers Acceptance | First Credit Facility Expires June 2016

Debt Instrument [Line Items]

Line of credit maximum borrowing capacity

$ 34,900,000

¥ 240,000,000

Debt instrument, basis spread

4.10%

China | Notes Payable to Banks | Note payable to China CITIC Bank

Debt Instrument [Line Items]

Repayments of lines of credit

$ 17,000,000

Minimum | Mitsubishi Bank

Debt Instrument [Line Items]

Interest rate

1.05%

1.05%

1.05%

1.05%

1.05%

1.05%

Minimum | Wells Fargo Credit Facility | Line of Credit

Debt Instrument [Line Items]

Revolver accounts receivable

80.00%

Minimum | Wells Fargo Credit Facility | Credit Facility Base Rate | Line of Credit

Debt Instrument [Line Items]

Debt instrument, basis spread

1.50%

Minimum | Wells Fargo Credit Facility | Prime Rate | Line of Credit

Debt Instrument [Line Items]

Debt instrument, basis spread

0.50%

Maximum | Mitsubishi Bank

Debt Instrument [Line Items]

Interest rate

1.45%

1.45%

1.45%

1.45%

1.45%

1.45%

Maximum | Wells Fargo Credit Facility | Line of Credit

Debt Instrument [Line Items]

Revolver accounts receivable

85.00%

Maximum | Wells Fargo Credit Facility | Credit Facility Base Rate | Line of Credit

Debt Instrument [Line Items]

Debt instrument, basis spread

1.75%

Maximum | Wells Fargo Credit Facility | Prime Rate | Line of Credit

Debt Instrument [Line Items]

Debt instrument, basis spread

0.75%

Financial Standby Letter of Credit

Debt Instrument [Line Items]

Outstanding letters of credit

$ 1,600,000

Subsequent Event | Wells Fargo Credit Facility | Line of Credit

Debt Instrument [Line Items]

Repayments of lines of credit

$ 5,000,000

Debt - Maturities of Long-Term

Debt - Maturities of Long-Term debt (Details) $ in Thousands	Dec. 31, 2018USD ($)
Debt Disclosure [Abstract]
2,019	$ 3,058
2,020	3,058
2,021	3,058
2,022	39,019
2,023	3,058
Thereafter	2,702
Long Term Debt	$ 53,953

Pension Plans - Narrative (Deta

Pension Plans - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2015USD ($)	May 31, 2014USD ($)	Dec. 31, 2013defined_benfit_plan
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | defined_benfit_plan							2
Plan assets	$ 0	$ 0	$ 0		$ 0
Cost of Goods and Services Sold	256,367	231,415	294,290
Operating expenses	$ 107,831	$ 112,843	$ 114,114
Discount rate	0.10%	0.10%
Reclassification out of Accumulated Other Comprehensive Income
Defined Benefit Plan Disclosure [Line Items]
Cost of Goods and Services Sold				$ 200
Operating expenses				$ 100
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Plan assets						$ 2,000
Receivable from LAPIS						$ 300

Pension Plans - Funded Status (

Pension Plans - Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in projected benefit obligation:
Projected benefit obligation, beginning of period	$ 4,616	$ 4,802	$ 5,086
Service cost	0	0	0
Interest cost	4	5	11
Benefits paid	(517)	(411)	(551)
Actuarial (gain)/loss	95	32	72
Curtailment/Settlement	0	0	0
Transfer from DBCPP to RAP	0	0	0
Currency translation adjustment	110	188	184
Projected benefit obligation, end of period	4,308	4,616	4,802
Change in plan assets:
Plan assets at fair value, beginning of period	0	0	0
Employer contributions	0
Benefits paid	0
Transfer to DCP	0
Currency translation adjustment	0
Plan assets at fair value, end of period	0	0	0
Amounts recognized in consolidated balance sheets:
Accrued and other current liabilities	257	488	393
Other noncurrent liabilities	4,051	4,128	4,409
Amount recognized in accumulated other comprehensive loss:
Defined benefit pension plans adjustment	373	271	230
Accumulated benefit obligation, end of period	$ 4,308	$ 4,616	$ 4,802

Pension Plans - Periodic Pensio

Pension Plans - Periodic Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Service cost	$ 0	$ 0	$ 0
Interest cost	4	5	11
Other	0	0	0
Curtailment/settlement (gain) loss	0	0	0
Net periodic pension costs	$ 4	$ 5	$ 11

Pension Plans - Estimated Futur

Pension Plans - Estimated Future Benefit Payments Under Plans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
2,019	$ 188
2,020	513
2,021	626
2,022	295
2,023	0
2024 - 2026	1,631
Thereafter	1,055
Defined benefit plan, benefit obligation	$ 4,308	$ 4,616	$ 4,802	$ 5,086

Pension Plans - 401 (k) Plan (D

Pension Plans - 401 (k) Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Matching contributions to 401(k) plan	$ 0.4	$ 0.5	$ 0.4

Commitments and contingencies -

Commitments and contingencies - Narrative (Details) ¥ in Thousands, ft² in Thousands, € in Millions

Jun. 13, 2017USD ($)ft²

Sep. 16, 2013USD ($)

Jun. 30, 2019USD ($)

Feb. 28, 2019USD ($)

Feb. 28, 2019CNY (¥)

Dec. 31, 2018USD ($)

Nov. 30, 2018USD ($)

Sep. 30, 2018USD ($)

Jul. 31, 2018USD ($)

Apr. 30, 2018USD ($)lawsuit

Oct. 31, 2017USD ($)

Oct. 31, 2017CNY (¥)

Jun. 30, 2017USD ($)

Apr. 30, 2017USD ($)

Dec. 31, 2016USD ($)

Nov. 30, 2016lawsuit

Sep. 30, 2016USD ($)ft²

Mar. 31, 2015USD ($)

Mar. 31, 2015EUR (€)

Mar. 07, 2019USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Jan. 31, 2019USD ($)

Dec. 31, 2015USD ($)

Dec. 31, 2012USD ($)claim

Dec. 31, 2010claim

Commitments And Contingencies Disclosure [Line Items]

Area of office lease | ft²

39

64

Office lease term, months

123 months

129 months

Expected lease restoration charges

$ 700,000

$ 3,100,000

Lease period, with no rent charge

9 months

Operating leases, future minimum, sublease receipts

$ 1,300,000

$ 1,300,000

Rent expense

4,200,000

$ 4,600,000

$ 2,400,000

Total outstanding purchase obligations

50,900,000

50,900,000

Fair value of derivative

2,000,000

2,000,000

$ 400,000

Laser2000 Case

Commitments And Contingencies Disclosure [Line Items]

Payments for legal settlements

$ 250,000

Lawsuit filed by Lestina International Ltd.

Commitments And Contingencies Disclosure [Line Items]

Damages sought

$ 3,000,000

APAT OE Legal Dispute

Commitments And Contingencies Disclosure [Line Items]

Damages sought

$ 20,000,000

APAT OE And NeoChina

Commitments And Contingencies Disclosure [Line Items]

Litigation, assets preserved

$ 29,000,000

29,000,000

Lawsuit filing period

30 days

Apat Optoelectronics Components Co Arbitration

Commitments And Contingencies Disclosure [Line Items]

Damages sought

$ 7,800,000

$ 12,000,000

$ 1,500,000

$ 1,500,000

Proceeds from legal settlements

$ 110,000

¥ 700

Cisco settlement agreement

Commitments And Contingencies Disclosure [Line Items]

Litigation settlement, amount awarded to other party

$ 300,000

Amount awarded to other party, production credits

$ 150,000

Minimum

Commitments And Contingencies Disclosure [Line Items]

Office lease, monthly rental rate

41,388

$ 144,000

Maximum

Commitments And Contingencies Disclosure [Line Items]

Office lease, monthly rental rate

$ 72,525

$ 194,000

Pending Litigation | Laser2000 Case

Commitments And Contingencies Disclosure [Line Items]

Estimated litigation liability

$ 300,000

Infringement of United States Patents | Finisar

Commitments And Contingencies Disclosure [Line Items]

Claims of patent infringement | claim

4

2

Termination Of Distributor Agreement | Pending Litigation | Laser 2000

Commitments And Contingencies Disclosure [Line Items]

Partial settlement of claims payment

$ 492,000

Accrual for estimated net litigation expense

$ 1,100,000

€ 1

Private Placement | Performance Guarantee

Commitments And Contingencies Disclosure [Line Items]

Other non-current liability

$ 6,700,000

$ 6,700,000

$ 30,000,000

Embedded Derivative Financial Instruments | Maximum

Commitments And Contingencies Disclosure [Line Items]

Other non-current liability

$ 5,000,000

Forecast | RUSSIAN FEDERATION

Commitments And Contingencies Disclosure [Line Items]

Exit fees for future

$ 2,000,000

Subsequent Event | APAT OE And NeoChina

Commitments And Contingencies Disclosure [Line Items]

Litigation, pre-trial preservation order, additional assets ordered to be preserved

$ 3,800,000

Subsequent Event | APAT OE Versus NeoChina, NeoPhotonics Corporation Limited, Novel Centennial Limited And NeoPhotonics Corporation

Commitments And Contingencies Disclosure [Line Items]

Damages sought

$ 36,000,000

Rusnano Group | NeoPhotonics Corporation, LLC | Disposal Group, Disposed of by Sale, Not Discontinued Operations

Commitments And Contingencies Disclosure [Line Items]

Disposal group, including discontinued operation, ownership in disposed subsidiary

100.00%

100.00%

Disposal group, including discontinued operation, consideration

$ 3,000,000

$ 3,000,000

Disposal group, including discontinued operation, penalty payment cancellation

$ 1,000,000

1,000,000

NeoPhotonics Dongguan Co., Ltd | Lestina International Ltd. | Lawsuit filed by Lestina International Ltd.

Commitments And Contingencies Disclosure [Line Items]

Litigation settlement, amount awarded to other party

$ 2,200,000

NeoPhotonics Dongguan Co., Ltd | Lestina International Ltd. | Forecast | Lawsuit filed by Lestina International Ltd.

Commitments And Contingencies Disclosure [Line Items]

Damages paid

$ 1,000,000

$ 1,200,000

APAT OE | APAT OE Legal Dispute

Commitments And Contingencies Disclosure [Line Items]

Patent lawsuit filed | lawsuit

3

NeoChina | Subsequent Event | Claim Against APAT OE And Zheijiang Merchants Property Insurance Company

Commitments And Contingencies Disclosure [Line Items]

Damages sought | ¥

¥ 350

Oyster Communications, Inc.

Commitments And Contingencies Disclosure [Line Items]

Patent lawsuit filed | lawsuit

9

Commitments and contingencies_2

Commitments and contingencies - Future minimum commitments under the Company's non-cancelable operating leases (Details) $ in Thousands	Dec. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,019	$ 3,618
2,020	3,113
2,021	3,059
2,022	3,056
2,023	3,049
Thereafter	11,437
Total future minimum lease payments	$ 27,332

Stockholders' Equity - Common s

Stockholders' Equity - Common stock, resale registration statement, and follow-on public offering (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, par value (USD per share)	$ 0.0025	$ 0.0025
Public offering price (USD per share)				$ 7.25
Proceeds from issuance of common stock				$ 45,600
Underwriting discounts				3,000
Other offering expenses				$ 1,200
Reclassified out of accumulated other comprehensive loss for realized gains or losses on available for sale securities	$ 0	$ 0	$ 0
Retained earnings subject to restriction	$ 9,000	$ 8,800
Resale Registration Statement
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			4,972,905	4,972,905
Common stock, par value (USD per share)			$ 0.0025	$ 0.0025
Minimum
Class of Stock [Line Items]
Accumulated profits	10.00%
Employee stock options
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	7,486,096
Employee stock purchase plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	474,462
Common stock | Follow-on public offering
Class of Stock [Line Items]
Issuance of common stock from public stock offering, net of discount and offering costs (in shares)				6,866,689
Common stock | Over-Allotment Option
Class of Stock [Line Items]
Issuance of common stock from public stock offering, net of discount and offering costs (in shares)				895,655

Stockholders' Equity - Accumula

Stockholders' Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ 160,240	$ 194,451	$ 225,405	$ 211,656
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(6,897)	567
Unrealized loss on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	0	(1)
Defined benefit pension plan adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	229	168
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ (7,126)	$ 398	$ (8,401)	$ (1,723)

Stock-based compensation - Narr

Stock-based compensation - Narrative (Details) $ / shares in Units, $ in Thousands	Dec. 18, 2014USD ($)installment$ / sharesshares	Feb. 28, 2011shares	Apr. 30, 2010shares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015$ / sharesshares	Dec. 31, 2014$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remitted cash to appropriate tax authorities | $				$ 954	$ 998	$ 615
Stock Appreciation Units (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase shares, outstanding (in shares)				192,872	239,824
Intrinsic value of options exercised | $				$ 100	$ 200	500
Number of days for stock price to be traded above mentioned price				20 days
Minimum closing stock price (USD per share) | $ / shares				$ 15
Share-based compensation expense (gain) | $				$ (100)	(300)
Stock grants vested value | $				$ 0	$ 0	3,700
Employee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase shares, outstanding (in shares)				3,202,745	3,933,529
Shares available for future grant (in shares)				1,102,323	959,136
Authorized for issuance (in shares)				1,947,667
Unrecognized stock-based compensation expense | $				$ 1,800
Fair value of options vested | $				2,300	$ 1,500	3,900
Intrinsic value of options exercised | $				$ 2,400	$ 3,000	$ 9,700
Weighted-average fair value of options granted (USD per share) | $ / shares				$ 4.03	$ 4.43	$ 7.05
Remaining weighted-average period				1 year 9 months 12 days
Stock Option and Restricted Stock Unit Activity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market-based restricted stock units (in shares)				800,000
Weighted-average fair value granted (USD per share) | $ / shares							$ 4.72
Number of days for stock price to be traded above mentioned price				20 days
Minimum closing stock price (USD per share) | $ / shares				$ 15
Share-based compensation expense (gain) | $						$ 4,800
Stock Option and Restricted Stock Unit Activity | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value granted (USD per share) | $ / shares								$ 1.65
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)				2,486,028	2,404,637
Unrecognized stock-based compensation expense | $				$ 13,200
Remaining weighted-average period				2 years 1 month 6 days
Market-based restricted stock units (in shares)				1,446,940
Weighted-average fair value granted (USD per share) | $ / shares				$ 6.83	$ 7.86	$ 12.33
Stock grants vested value | $				$ 9,800	$ 7,600	$ 1,600
Aggregate intrinsic value, vested | $				$ 7,400	$ 6,400	$ 2,800
Common stock withheld shares (in shares)				147,572	126,999	49,838
Remitted cash to appropriate tax authorities | $				$ 1,000	$ 1,000	$ 600
Vested (in shares)				1,123,893
Market-based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards expiration period from date of grant				7 years
Remaining weighted-average period				3 years 6 months
Market-based restricted stock units (in shares)				695,000
Weighted-average fair value granted (USD per share) | $ / shares				$ 5.82
Vested (in shares)				0
Employee service share-based compensation, nonvested awards, compensation not yet recognized, stock options | $				$ 2,900
Remaining contractual term				6 years 6 months
Stock Appreciation Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase shares, outstanding (in shares)				200,000
Liability for settlement | $				$ 600	$ 800
2004 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase shares, outstanding (in shares)				273,685
Shares available for future grant (in shares)				0
2007 Stock Appreciation Grants Plan | Stock Appreciation Units (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)				27,872
2010 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant (in shares)				835,575
Shares outstanding (in shares)				5,553,442
Awards expiration period from date of grant				10 years
Maximum aggregate number of shares of common stock that may be issued (in shares)			865,420	8,000,000
Number of shares of common stock outstanding increase percentage			3.50%
2010 Equity Incentive Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, percentage of fair value of common stock on grant date				100.00%
Options vesting period				3 years
2010 Equity Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period				4 years
2010 Equity Incentive Plan | Nonqualified Stock Options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, percentage of fair value of common stock on grant date				85.00%
2010 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant (in shares)				474,462
Maximum aggregate number of shares of common stock that may be issued (in shares)		342,568		600,000
Number of shares of common stock outstanding increase percentage		3.50%
Offering period				12 months
2011 Inducement Award Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant (in shares)				266,748
Shares outstanding (in shares)				556,646
Exercise price, percentage of fair value of common stock on grant date		100.00%
Awards expiration period from date of grant		10 years
Maximum aggregate number of shares of common stock that may be issued (in shares)		750,000
Authorized for issuance (in shares)							100,000
2014 Repricing Offer | Stock Appreciation Units (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued under repricing offer (in shares)	87,354
2014 Repricing Offer | Stock Options and Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued under repricing offer (in shares)	2,373,692
Incremental compensation cost | $	$ 900
Unrecognized stock-based compensation expense | $	$ 2,600
Exercise price per share (USD per share) | $ / shares	$ 3.50
Percentage of shares subject to repriced eligible stock	50.00%
Number of monthly installments | installment	12
Remaining vesting term	60 days
Period prior to expiration date when repriced awards vested and become exercisable	60 days
2014 Repricing Offer | Stock Options and Stock Appreciation Rights | Vesting In 12 Equal Monthly Installments
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares subject to repriced eligible stock	50.00%
2014 Repricing Offer | Stock Options and Stock Appreciation Rights | 60th Day Prior to Expiration Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares subject to repriced eligible stock	100.00%
2014 Repricing Offer | Employee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued under repricing offer (in shares)	1,948,631

Stock-based compensation - Assu

Stock-based compensation - Assumptions (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected term (years)	6 years 7 days	5 years 11 months 27 days	5 years 9 months
Weighted-average volatility	65.00%	65.00%	65.00%
Risk-free interest rate Minimum	2.27%	2.02%	1.01%
Risk-free interest rate Maximum	2.62%	2.08%	1.76%
Expected dividends	0.00%	0.00%	0.00%
Stock Appreciation Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected term (years)	1 year 11 months 10 days	2 years 3 months 18 days	2 years 9 months 7 days
Weighted-average volatility	66.00%	69.00%	61.00%
Risk-free interest rate Minimum	1.03%	0.51%	0.45%
Risk-free interest rate Maximum	2.81%	1.62%	1.47%
Expected dividends	0.00%	0.00%	0.00%
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected term (years)	8 months 19 days	8 months 19 days	8 months 23 days
Weighted-average volatility	61.00%	61.00%	54.00%
Risk-free interest rate Minimum	1.93%	0.91%	0.39%
Risk-free interest rate Maximum	2.59%	1.31%	0.45%
Expected dividends	0.00%	0.00%	0.00%
Market-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average volatility	66.00%	0.00%
Risk-free interest rate	2.79%	0.00%
Expected dividends	0.00%	0.00%

Stock-based compensation - Summ

Stock-based compensation - Summary of stock compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation	$ 14,142	$ 8,206	$ 17,076
Cost of goods sold
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation	2,596	1,098	3,130
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation	3,570	2,491	4,760
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation	3,248	1,697	4,105
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation	$ 4,728	$ 2,920	$ 5,081

Stock-based compensation - Stoc

Stock-based compensation - Stock Options and RSUs (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee stock options
Shares Available for Grant
Beginning Balance (in shares)	959,136
Authorized for issuance (in shares)	1,947,667
Granted (in shares)	(2,300,056)
Exercised/Converted (in shares)	0
Cancelled/Forfeited (in shares)	(495,576)
Ending Balance (in shares)	1,102,323	959,136
Number of Shares
Beginning Balance (in shares)	3,933,529
Authorized for issuance (in shares)	0
Granted (in shares)	158,116
Exercised/Converted (in shares)	(778,811)
Cancelled/Forfeited (in shares)	(110,089)
Ending Balance (in shares)	3,202,745	3,933,529
Weighted Average Exercise Price
Beginning Balance (USD per share)	$ 5.55
Authorized for issuance (in shares)	0
Granted (USD per share)	6.64
Exercised/Converted (USD per share)	4.39
Cancelled/Forfeited (USD per share)	10.07
Ending Balance (USD per share)	$ 5.73	$ 5.55
Restricted stock units
Number of Units
Beginning Balance (in shares)	2,404,637
Authorized for issuance (in shares)	0
Granted (in shares)	1,446,940
Exercised/Converted (in shares)	(1,123,893)
Cancelled/Forfeited (in shares)	(241,656)
Ending Balance (in shares)	2,486,028	2,404,637
Weighted Average Exercise Price
Beginning Balance (USD per share)	$ 9.02
Authorized for issuance (in shares)	0
Granted (USD per share)	6.83	$ 7.86	$ 12.33
Exercised/Converted (USD per share)	8.82
Cancelled/Forfeited (USD per share)	8.74
Ending Balance (USD per share)	$ 7.87	$ 9.02

Stock-based compensation - Su_2

Stock-based compensation - Summary of Information about Stock Options Outstanding (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Number of Shares
Vested and expected to vest (in shares) | shares	3,152,837
Exercisable (in shares) | shares	2,701,433
Weighted Average Exercise Price
Vested and expected to vest (USD per share) | $ / shares	$ 5.70
Exercisable (USD per share) | $ / shares	$ 5.32
Weighted Average Remaining Contractual Term (Years)
Vested and expected to vest	5 years 3 months 22 days
Exercisable	4 years 9 months 11 days
Aggregate Intrinsic Value (in Thousands)
Vested and expected to vest | $	$ 4,936,208
Exercisable | $	$ 4,864,959

Stock-based compensation - Su_3

Stock-based compensation - Summary of Information about Restricted Stock Units Outstanding (Details) - Restricted stock units $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Number of Shares
Vested and expected to vest (in shares) | shares	2,166,565
Weighted Average Exercise Price
Vested and expected to vest (in USD per share) | $ / shares	$ 0
Weighted Average Remaining Contractual Term (Years)
Vested and expected to vest	1 year 3 months 4 days
Aggregate Intrinsic Value
Vested and expected to vest | $	$ 14,039,340

Stock-based compensation - Su_4

Stock-based compensation - Summary of Company's Stock Appreciation Unit Activity (Details) - Stock Appreciation Units (SARs)	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Number of Units
Beginning Balance (in shares) | shares	239,824
Exercised/Converted (in shares) | shares	(31,272)
Cancelled/Forfeited (in shares) | shares	(15,680)
Ending Balance (in shares) | shares	192,872
Weighted-Average Exercise Price
Beginning Balance (USD per share) | $ / shares	$ 4.95
Exercised/Converted (USD per share) | $ / shares	4.32
Cancelled/Forfeited (USD per share) | $ / shares	6.72
Ending Balance (USD per share) | $ / shares	$ 4.91

Stock-based compensation - Empl

Stock-based compensation - Employee Stock Purchase Plan (Details) - Employee stock purchase plan $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock under employee stock purchase plan (in shares) | shares	404,211
Unrecognized stock-based compensation expense | $	$ 0.8

Income taxes - Income (Loss) be

Income taxes - Income (Loss) before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S. operations	$ (43,384)	$ (52,725)	$ (10,217)
Non-U.S. operations	1,076	301	13,609
Income (loss) before income taxes	$ (42,308)	$ (52,424)	$ 3,392

Income taxes - Components of Pr

Income taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current
Federal	$ (49)	$ (144)	$ (127)
State	36	3	(13)
Foreign	(1,634)	363	(3,925)
Provision for income tax, current	(1,647)	222	(4,065)
Deferred
Federal	42	4	(24)
State	0	0	0
Foreign	276	(1,135)	492
Total provision	$ (1,329)	$ (909)	$ (3,597)

Income taxes - Narrative (Detai

Income taxes - Narrative (Details) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Change in prior year deferred balances	$ (1,653,000)	$ 28,262,000	$ (920,000)
Tax Cuts and Jobs Act of 2017 tax expense		30,000,000
Valuation allowance, increase (decrease)	16,800,000	(14,000,000)
Income Tax Examination [Line Items]
Cumulative effect of new accounting standard				$ (1,824,000)
Effective income tax rate reconciliation, share-based compensation, excess tax benefit, amount	8,600,000
Unrecognized tax benefits	26,196,000	$ 25,539,000	$ 23,606,000		$ 20,686,000
Unrecognized tax benefits that would impact the effective tax rate	100,000
Unrecognized tax benefits, income tax penalties and interest expense	0
Domestic Tax Authority
Income Tax Examination [Line Items]
Operating loss carryforwards	276,600,000
State and Local Jurisdiction
Income Tax Examination [Line Items]
Operating loss carryforwards	52,000,000
Accounting Standards Update 2016-16
Income Tax Examination [Line Items]
Cumulative effect of new accounting standard				$ 1,800,000
Research Tax Credit Carryforward | Domestic Tax Authority
Income Tax Examination [Line Items]
Tax credit carryforward	9,400,000
Research Tax Credit Carryforward | State and Local Jurisdiction
Income Tax Examination [Line Items]
Tax credit carryforward	17,300,000
Research Tax Credit Carryforward | Foreign Tax Authority
Income Tax Examination [Line Items]
Tax credit carryforward	$ 10,500,000

Income taxes - Difference in Pr

Income taxes - Difference in Provision for Income Taxes from Amount Obtained by Applying U.S. Federal Statutory Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory rate	21.00%	35.00%	35.00%
Tax at federal statutory rate	$ 8,869	$ 18,354	$ (1,185)
State taxes, net of federal benefit	36	2	(8)
Mandatory repatriation/Section 956	0	(5,718)	(19)
Nondeductible expenses	(371)	(67)	(727)
Stock-based compensation	(1,079)	(314)	(877)
Change in valuation allowance	(10,094)	16,273	(1,455)
Research and development	914	851	1,175
Foreign rate differences	(697)	(2,819)	(1,215)
Foreign tax credit	49	144	127
Change in prior year deferred balances	1,653	(28,262)	920
Other	(609)	647	(333)
Total provision	$ (1,329)	$ (909)	$ (3,597)

Income taxes - Components of De

Income taxes - Components of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets:
Net operating loss carryforwards	$ 56,828	$ 44,912
Federal and state credits	28,328	26,170
Reserves, accruals and other	11,265	9,698
Fixed assets and intangibles	2,398	1,259
Total deferred tax assets	98,819	82,039
Valuation allowance	(92,891)	(76,101)
Total deferred tax assets, net of valuation allowance	5,928	5,938
Less deferred tax liabilities:
Acquired intangibles	(313)	(2,054)
Property, plant and equipment	(4,754)	(3,338)
Net deferred tax assets	861	546
Reported as:
Long term deferred tax assets, included within other long-term assets	861	652
Long term deferred income tax liabilities, included within noncurrent liabilities	0	(106)
Net deferred tax assets	$ 861	$ 546

Income taxes - Reconciliation o

Income taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 25,539	$ 23,606	$ 20,686
Gross increases for tax positions of current year	657	1,933	2,920
Ending Balance	$ 26,196	$ 25,539	$ 23,606

Segment and geographic Inform_3

Segment and geographic Information - Additional Information (Details) - segment	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting [Abstract]
Number of reportable segments	1	1	1

Segment and geographic inform_4

Segment and geographic information (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 100,090	$ 127,565
China
Segment Reporting Information [Line Items]
Property, plant and equipment, net	27,329	37,212
United States
Segment Reporting Information [Line Items]
Property, plant and equipment, net	29,054	42,243
Japan
Segment Reporting Information [Line Items]
Property, plant and equipment, net	29,631	43,826
Rest of world
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 14,076	$ 4,284

Selected Quarterly Financial _3

Selected Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Selected Quarterly Financial Information [Abstract]
Revenue	$ 91,104	$ 81,748	$ 81,102	$ 68,586	$ 76,871	$ 71,121	$ 73,214	$ 71,688	$ 322,540	$ 292,894	$ 411,423
Gross profit	22,586	18,933	15,472	9,182	15,686	10,513	16,777	18,503	66,173	61,479	117,133
Net loss	$ (6,729)	$ (8,125)	$ (10,537)	$ (18,246)	$ (14,283)	$ (18,187)	$ (9,341)	$ (11,522)	$ (43,637)	$ (53,333)	$ (205)
Basic net loss per share (USD per share)	$ (0.15)	$ (0.18)	$ (0.24)	$ (0.41)	$ (0.32)	$ (0.42)	$ (0.22)	$ (0.27)	$ (0.97)	$ (1.23)	$ 0
Diluted net loss per share (USD per share)	$ (0.15)	$ (0.18)	$ (0.24)	$ (0.41)	$ (0.32)	$ (0.42)	$ (0.22)	$ (0.27)	$ (0.97)	$ (1.23)	$ 0
Weighted average shares used to compute basic net loss per share (in shares)	46,150	45,476	44,665	44,259	44,079	43,790	43,219	42,615	45,144	43,431	41,798
Weighted average shares used to compute diluted net loss per share (in shares)	46,150	45,476	44,665	44,259	44,079	43,790	43,219	42,615	45,144	43,431	41,798

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended	12 Months Ended
	Jan. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Depreciation			$ 29.9	$ 27	$ 17.9
Line of Credit | Wells Fargo Credit Facility | Subsequent Event
Subsequent Event [Line Items]
Repayments of lines of credit	$ 5
Lestina
Subsequent Event [Line Items]
Settlement agreement, paid			$ 2.2
Forecast | Subsequent Event
Subsequent Event [Line Items]
Depreciation		$ 3

Uncategorized Items - nptn-2018

Label	Element	Value
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (1,824,000)