Neophotonics (NPTN) 10-K 25 Feb 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Feb. 19, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-35061
Entity Registrant Name	NeoPhotonics Corp
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-3253730
Entity Address, Address Line One	3081 Zanker Road
Entity Address, City or Town	San Jose
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95134
City Area Code	408
Local Phone Number	232-9200
Title of 12(b) Security	Common Stock, par value $0.0025 per share
Trading Symbol	NPTN
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 431,164
Entity Common Stock, Shares Outstanding		50,782,036
Documents Incorporated by Reference	The Registrant has incorporated by reference into Part III of this Annual Report on Form 10-K portions of its Proxy Statement for its 2020 Annual Meeting of Stockholders to be filed pursuant to Regulation 14A. The Proxy Statement will be filed within 120 days of Registrant’s fiscal year ended December 31, 2020.
Entity Central Index Key	0001227025
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 95,117	$ 70,467
Short-term investments	27,669	7,638
Restricted cash	489	10,972
Accounts receivable, net of allowance for doubtful accounts	45,232	68,890
Inventories	46,901	46,930
Prepaid expenses and other current assets	20,173	25,851
Total current assets	235,581	230,748
Property, plant and equipment, net	66,765	81,133
Operating lease right-of-use assets	13,823	15,603
Purchased intangible assets, net	1,468	2,151
Goodwill	1,115	1,115
Other long-term assets	4,912	3,929
Total assets	323,664	334,679
Current liabilities:
Accounts payable	43,539	58,554
Current portion of long-term debt	3,232	3,044
Accrued and other current liabilities	42,053	47,481
Total current liabilities	88,824	109,079
Long-term debt, net of current portion	30,327	39,237
Operating lease liabilities, non-current	14,522	16,543
Other noncurrent liabilities	9,584	9,614
Total liabilities	143,257	174,473
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, 100,000 shares authorized At December 31, 2020, 50,457 shares issued and outstanding; at December 31, 2019, 48,526 shares issued and outstanding	126	121
Additional paid-in capital	597,460	582,504
Accumulated other comprehensive income (loss)	1,735	(7,871)
Accumulated deficit	(418,914)	(414,548)
Total stockholders’ equity	180,407	160,206
Total liabilities and stockholders’ equity	$ 323,664	$ 334,679
Preferred stock, par value (USD per share)	$ 0.0025	$ 0.0025
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
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)	50,457,000	48,526,000
Common stock, shares outstanding (in shares)	50,457,000	48,526,000

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
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)	50,457,000	48,526,000
Common stock, shares outstanding (in shares)	50,457,000	48,526,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue	$ 371,163	$ 356,804	$ 322,540
Cost of goods sold	268,081	267,991	256,367
Gross profit	103,082	88,813	66,173
Operating expenses:
Research and development	56,100	57,634	53,818
Sales and marketing	15,629	16,088	16,728
General and administrative	30,569	29,759	30,403
Amortization of purchased intangible assets	0	119	475
Acquisition and asset sale related costs	1,094	397	427
Restructuring charges	156	261	3,135
Litigation settlements	(2,988)	0	2,645
Loss (gain) on asset sale	(1,044)	(903)	200
Total operating expenses	99,516	103,355	107,831
Income (loss) from operations	3,566	(14,542)	(41,658)
Interest income	182	376	397
Interest expense	(1,182)	(1,919)	(2,493)
Other income (expense), net	(5,730)	642	1,446
Total interest and other income (expense), net	(6,730)	(901)	(650)
Loss before income taxes	(3,164)	(15,443)	(42,308)
Provision for income taxes	(1,202)	(1,633)	(1,329)
Net loss	$ (4,366)	$ (17,076)	$ (43,637)
Basic and diluted net loss per share (USD per share)	$ (0.09)	$ (0.36)	$ (0.97)
Weighted average shares used to compute basic and diluted net loss per share (in shares)	49,474	47,304	45,144

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (4,366)	$ (17,076)	$ (43,637)
Other comprehensive income (loss):
Foreign currency translation adjustments, net of zero tax	9,592	(745)	(7,464)
Unrealized gain on available-for-sale securities, net of zero tax	0	0	1
Defined benefit pension plans:
Loss arising during the period	21	0	(95)
Tax	(7)	0	34
Total other comprehensive income (loss)	9,606	(745)	(7,524)
Comprehensive income (loss)	$ 5,240	$ (17,821)	$ (51,161)

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
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	Revision of Prior Period, Accounting Standards Update, Adjustment	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit	Accumulated deficitRevision of Prior Period, Accounting Standards Update, Adjustment
Beginning balance (in shares) at Dec. 31, 2017			44,219
Beginning balance at Dec. 31, 2017	$ 194,451	$ (1,824)	$ 111	$ 545,953	$ 398	$ (352,011)	$ (1,824)
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive loss	(17,821)				(745)	(17,076)
Issuance of common stock in exchange for research and development services, net of issuance costs of $46 (in shares)			442
Issuance of common stock in exchange for research and development services, net of issuance costs of $46	2,454		$ 1	2,453
Issuance of common stock upon exercise of stock options (in shares)			486
Issuance of common stock upon exercise of stock options	1,893		$ 1	1,892
Issuance of common stock under employee stock purchase plan (in shares)			357
Issuance of common stock under employee stock purchase plan	1,953		$ 1	1,952
Issuance of common stock for vested restricted stock units (in shares)			1,018
Issuance of common stock for vested restricted stock units	0		$ 2	(2)
Tax withholding related to vesting of restricted stock units (in shares)			(155)
Tax withholding related to vesting of restricted stock units	(733)			(733)
Stock-based compensation costs	12,220			12,220
Ending balance (in shares) at Dec. 31, 2019			48,526
Ending balance at Dec. 31, 2019	160,206		$ 121	582,504	(7,871)	(414,548)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive loss	5,240				9,606	(4,366)
Issuance of common stock upon exercise of stock options (in shares)			498
Issuance of common stock upon exercise of stock options	2,172		$ 2	2,170
Issuance of common stock under employee stock purchase plan (in shares)			326
Issuance of common stock under employee stock purchase plan	2,141		$ 1	2,140
Issuance of common stock for vested restricted stock units (in shares)			1,313
Issuance of common stock for vested restricted stock units	0		$ 3	(3)
Tax withholding related to vesting of restricted stock units (in shares)			(206)
Tax withholding related to vesting of restricted stock units	(1,751)		$ (1)	(1,750)
Stock-based compensation costs	12,399			12,399
Ending balance (in shares) at Dec. 31, 2020			50,457
Ending balance at Dec. 31, 2020	$ 180,407		$ 126	$ 597,460	$ 1,735	$ (418,914)

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201616Member
Issuance costs	$ 46

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net loss	$ (4,366)	$ (17,076)	$ (43,637)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	30,648	30,788	31,105
Stock-based compensation expense	12,337	12,456	14,142
Deferred taxes	(928)	(287)	(328)
Amortization of investment, debt and other	360	414	438
Loss (gain) on disposal of property and equipment	(1,114)	(872)	1,322
Amortization of operating lease right-of-use assets	1,912	1,774	0
Net loss recovery from litigation settlement	(2,988)	0	0
Gain on foreign currency hedges	0	0	2,220
Allowance for doubtful accounts	(16)	(13)	61
Write-down of inventories	9,443	7,847	6,133
Foreign currency remeasurement and other, net	5,753	(910)	(3,944)
Issuance of common stock in exchange for research and development services	0	2,500	0
Change in assets and liabilities:
Accounts receivable	22,567	5,838	(7,874)
Inventories	(7,411)	(2,891)	7,368
Prepaid expenses and other assets	3,716	429	8,162
Accounts payable	(14,962)	(41)	(1,411)
Accrued and other liabilities	(21)	(5,269)	5,838
Net cash provided by operating activities	54,930	34,687	19,595
Cash flows from investing activities
Purchase of property, plant and equipment	(13,870)	(9,532)	(14,867)
Proceeds from sale of property, plant and equipment and other assets	533	2,242	32
Purchase of marketable securities	(23,531)	(157)	(920)
Proceeds from sale of marketable securities	3,500	0	5,000
Proceeds from maturity of marketable securities	0	0	750
Settlement of foreign currency hedges	0	0	(1,776)
Net cash used in investing activities	(33,368)	(7,447)	(11,781)
Cash flows from financing activities
Proceeds from exercise of stock options and issuance of stock under ESPP	3,880	3,846	5,614
Offering costs	0	(46)	0
Tax withholding on restricted stock units	(1,751)	(733)	(954)
Proceeds from bank loans	0	5,000	34,305
Repayment of bank loans	(10,150)	(18,084)	(63,040)
Proceeds from issuance of notes payable	0	0	7,137
Repayment of finance lease liabilities	(87)	(87)	0
Repayment of notes payable	0	(4,774)	(3,732)
Proceeds from (repayment of) government grants	(435)	0	1,210
Net cash used in provided by financing activities	(8,543)	(14,878)	(19,460)
Effect of exchange rates on cash, cash equivalents and restricted cash	1,148	(161)	(680)
Net increase (decrease) in cash, cash equivalents and restricted cash	14,167	12,201	(12,326)
Cash, cash equivalents and restricted cash at the beginning of the period	81,439	69,238	81,564
Cash, cash equivalents and restricted cash at the end of the period	95,606	81,439	69,238
Supplemental disclosure of cash flow information:
Cash paid for interest	248	278	1,600
Net cash paid (received) for income taxes	799	1,289	(1,383)
Supplemental disclosure of noncash investing and financing activities:
Neo Russia penalty settlement	0	2,000	0
Debt interest rolled into principal	701	1,368	0
Government approved expenditures incurred after receipt of government funds	0	579	0
Capital lease			362
Unpaid property, plant and equipment	$ 765	$ 1,887	$ 1,513

The Company and basis of presen

The Company and basis of presentation	12 Months Ended
	Dec. 31, 2020
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 and receive high-speed digital optical signals for Cloud and hyperscale data center internet content provider and telecom networks. 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; successful and timely completion of product design efforts; the ability of the Company to sell its new products into new market segments; trade restrictions by the United States against the Company's customers in China, as well as potential retaliatory trade actions taken by China; the loss of any of its larger customers; restrictions on the Company's ability to sell to foreign customers due to additional U.S. or new China trade laws, regulations and requirements; disruptions of the supply chain of components needed for its products; ability to obtain additional financing; inability to meet certain debt covenants; fundamental changes in the technology underlying the Company’s products; the hiring, training and retention of key employees; and new product design introductions by competitors. The inputs into the Company’s judgments and estimates consider the economic implications of the Covid-19 pandemic as the Company knows them, on its critical and significant accounting estimates. The extent to which the Covid-19 pandemic may impact its business will depend on future developments, which are highly uncertain, such as the duration of the outbreak, travel restrictions, governmental mandates issued to mitigate the spread of the disease, business closures, economic disruptions, and the effectiveness of actions taken to contain and treat the virus. Accordingly, future adverse developments with respect to the Covid-19 pandemic may have a negative impact on its sales, supply chain and results of operations. The inputs into the Company's judgments and estimates also consider the Department of Commerce Entities List restrictions on Huawei Technologies effective September 2020 for the Company and expected loss of business from Huawei Technologies. See also Note 10. 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.

Summary of significant accounti

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2020
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. 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 and recoverability of long-lived assets; valuation allowances for deferred tax assets; valuation of excess and obsolete inventories; warranty reserves; litigation accrual 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, 2020, 2019 and 2018 were as follows: Years Ended December 31, 2020 2019 2018 Percent of revenue from customers accounting for 10% or more of total revenue: Huawei Technologies Co., Ltd 40 % 41 % 46 % Ciena Corporation 17 % 29 % 24 % Acacia Communications, Inc. 10 % 5 % 2 % Percent of revenue from top five customers 79 % 84 % 87 % As of December 31, 2020, three customers accounted for a total of 65% of the Company’s total accounts receivable. As of December 31, 2019, two customers accounted for a total of 56% 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 9), 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, 2020, the majority of the restrictions on cash have been released. As of December 31, 2020 and 2019, the amount of restricted cash was $0.5 million and $11.0 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. 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 2020, 2019 and 2018. 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 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. Due to the Department of Commerce Entities List restrictions effective September 2020 and expected loss of business from Huawei, the Company performed a recoverability test in the third and fourth quarters of 2020 and determined there was no impairment of long-lived assets. There were no asset impairment charges in 2020 and 2019. The Company incurred asset impairment charges of $1.0 million in 2018. Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in operating lease right-of-use ("ROU") assets, other current liabilities and operating lease liabilities on the Company's consolidated balance sheet. Finance leases are included in property, plant and equipment, current portion of long-term debt and long-term debt, net of current portion on the consolidated balance sheets. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. As most of our leases do not provide an implicit rate, the Company uses an estimate of its incremental borrowing rate based on observed market data and other information available at the lease commencement date. The operating lease ROU assets also include any lease payments made and exclude lease incentives. Lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. The Company does not record leases on the consolidated balance sheet with a term of one year or less. The Company does not separate lease and non-lease components but rather account for each separate component as a single lease component for all underlying classes of assets. Variable lease payments are expensed as incurred and are not included within the operating lease ROU asset and lease liability calculation. Variable lease payments primarily include reimbursements of costs incurred by lessors for common area maintenance and utilities. Lease expense for minimum operating lease payments is recognized on a straight-line basis over the lease term. 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 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 ability to realize 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. 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 $2.2 million loss in 2018 relating to its foreign currency contracts within other income, net. Net foreign exchange gain (loss) was ($5.9) million, $0.2 million, and $1.4 million in 2020, 2019, and 2018, 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. In the second half of 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. Reclassifications Certain prior year amounts have been reclassified to conform to the current year presentation. Accounting standards update recently adopted In January 2017, the Financial Accounting Standards Board ("FASB") issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (“ASU 2017-04”). 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. In November 2019, the FASB issued ASU 2019-10, according to which, the new standard is effective for smaller reporting companies (“SRC”) as defined by the SEC, for fiscal years beginning after December 15, 2022 including interim periods within those fiscal years. The Company early adopted ASU 2017-04 guidance on January 1, 2020. The adoption of this standard had no material impact on the Company’s consolidated financial statements and related disclosures. In February 2016, the Financial Accounting Standards Board ("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 using the modified retrospective transition method. In July 2018, the FASB issued ASU 2018- 11, Leases (ASC 842): Targeted Improvements. The update provides an optional transition method that allows entities to change the date of initial application to the beginning of the period of adoption. The Company adopted the guidance on January 1, 2019 under the optional transition method. Certain optional practical expedients are allowed. The Company elected the package of practical expedients permitted under the transition guidance, which allowed the Company to carryforward historical lease classification, assessment on whether a contract was or contains a lease, and initial direct costs for any leases that existed prior to January 1, 2019. The Company also elected to combine lease and non-lease components and to keep leases with an initial term of 12 months or less off the consolidated balance sheet. As a result of adopting Topic 842 on January 1, 2019, the Company recognized operating lease right-of-use assets of $17.3 million and corresponding operating lease liabilities of $20.8 million from existing leases on the Company's consolidated balance sheet. Refer to Note 12 for further details. The adoption of Topic 842 had no impact on the Company's consolidated statement of operations or consolidated statement of cash flows. Recent accounting standards update not yet effective 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. In November 2019, the FASB issued ASU 2019-10, according to which, the new standard is effective for smaller reporting companies (“SRC”) as defined by the SEC, for fiscal years beginning after December 15, 2022 including interim periods within those fiscal years. The Company is in the process of evaluating the impact and timing of the adoption on its consolidated financial statements and related disclosures. In December 2019, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes. This guidance is effective for fiscal years beginning after December 15, 2020, with early adoption permitted. The Company will adopt this ASU in the first quarter of 2021 and is currently evaluating the impact of this ASU on the consolidated financial statements and related disclosures.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Product revenue The Company develops, manufactures and sells optoelectronic products that transmit and receive high speed digital optical signals for Cloud and hyperscale data center internet content provider and telecom networks. Revenue is derived primarily from the sale of hardware products. The Company sells its products worldwide, primarily to leading network equipment manufacturers and users. 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. The Company's standard payment terms range from 30 to 90 days. Shipping and handling costs are included in the cost of goods sold. The Company presents revenue net of sales taxes and any similar assessments. The Company’s performance obligations relate to contracts with a duration of less than one year. The Company elected to apply the practical expedient provided in Accounting Standard Codification Topic 606, “Revenue from Contracts with Customers” and, therefore, is not required to disclose the aggregate amount of the transaction price allocated to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period. Contract Costs The Company recognizes the incremental direct costs of obtaining a contract, which consist of sales commissions, when control over the products they relate to transfers to the customer. Applying the practical expedient, the Company recognizes commissions as expense when incurred, as the amortization period of the commission asset the Company would have otherwise recognized is less than one year. 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, 2020 2019 2018 High Speed Products $ 340,015 $ 323,804 $ 275,803 Network Products and Solutions 31,148 33,000 46,737 Total revenue $ 371,163 $ 356,804 $ 322,540 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, designated shipping points are often in China or elsewhere in Asia (in thousands): Years Ended December 31, 2020 2019 2018 China $ 191,990 $ 186,157 $ 187,277 Thailand 70,709 55,385 37,357 Mexico 35,549 74,077 54,771 Rest of world 72,915 41,185 43,135 Total revenue $ 371,163 $ 356,804 $ 322,540 Deferred revenue The Company records deferred revenue when cash payments are received or due in advance of the Company's performance. There were no deferred revenue balances at December 31, 2020 and 2019. Contract assets Contract assets are rights to consideration in exchange for goods or services that the Company has transferred to a customer when such right is conditional on something other than the passage of time. The balance of contract assets are excluding any amounts presented as an accounts receivable. There were no contract assets balances as of December 31, 2020 and December 31, 2019.

Cash, cash equivalents, short-t

Cash, cash equivalents, short-term investments and restricted cash	12 Months Ended
	Dec. 31, 2020
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, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Cash and cash equivalents: Cash $ 95,117 70,467 Cash equivalents — — Cash and cash equivalents $ 95,117 $ 70,467 Short-term investments $ 27,669 $ 7,638 Restricted cash $ 489 $ 10,972 December 31, 2020 December 31, 2019 Cash and cash equivalents $ 95,117 $ 70,467 Restricted cash 489 10,972 Total cash, cash equivalents and restricted cash shown in the consolidated statement of cash flows $ 95,606 $ 81,439 The following table summarizes the Company’s unrealized gains and losses related to the short-term investments in marketable securities designated as available-for-sale (in thousands): As of December 31, 2020 As of December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Marketable securities: Money market funds 27,669 — — 27,669 7,638 — — 7,638 Total $ 27,669 $ — $ — $ 27,669 $ 7,638 $ — $ — $ 7,638 Reported as: Short-term investments 27,669 — — 27,669 7,638 — — 7,638 Total $ 27,669 $ — $ — $ 27,669 $ 7,638 $ — $ — $ 7,638 As of December 31, 2020 and 2019, maturities of marketable securities were as follows (in thousands): December 31, 2020 December 31, 2019 Less than 1 year $ 27,669 $ 7,638 Due in 1 to 2 years — — Due in 3 to 5 years — — Total $ 27,669 $ 7,638

Fair value measurements

Fair value measurements	12 Months Ended
	Dec. 31, 2020
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, 2020 December 31, 2019 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash equivalents and short-term investments: Money market funds $ 27,669 $ — $ — $ 27,669 $ 7,638 $ — $ — $ 7,638 Total $ 27,669 $ — $ — $ 27,669 $ 7,638 $ — $ — $ 7,638 Mutual funds held in Rabbi Trust, recorded in other long-term assets $ 810 $ — $ — $ 810 $ 616 $ — $ — $ 616 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, 2020 and 2019. 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, 2020 and 2019. 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. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis There were no assets and liabilities measured on a nonrecurring basis as of December 31, 2020 and 2019. 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.

Net loss per share

Net loss per share	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 Numerator: Net loss (4,366) $ (17,076) $ (43,637) Denominator: Weighted average shares used to compute per share amount: Basic 49,474 47,304 45,144 Dilutive effect of equity awards — — — Diluted 49,474 47,304 45,144 Basic net loss per share $ (0.09) $ (0.36) $ (0.97) Diluted net loss per share $ (0.09) $ (0.36) $ (0.97) December 31, 2020 2019 2018 Employee stock options 2,097 2,599 3,203 Restricted stock units 3,621 3,171 2,486 Market-based restricted stock units 612 641 695 Performance-based restricted stock units 90 — — Employee stock purchase plan 358 298 414 6,778 6,709 6,798

Purchased intangible assets

Purchased intangible assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Purchased intangible assets	Purchased intangible assets Purchased intangible assets consist of the following (in thousands): December 31, 2020 December 31, 2019 Gross Accumulated Net Gross Accumulated Net Technology and patents $ 37,637 $ (37,021) $ 616 $ 36,880 $ (35,555) $ 1,325 Customer relationships 15,487 (15,487) — 15,089 (15,089) — Leasehold interest 1,304 (452) 852 1,222 (396) 826 $ 54,428 $ (52,960) $ 1,468 $ 53,191 $ (51,040) $ 2,151 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, 2020 2019 2018 Cost of goods sold $ 737 $ 737 $ 756 Operating expenses — 119 475 Total $ 737 $ 856 $ 1,231 The gross assets and accumulated amortization for customer relationships includes the impact of foreign currency transaction gains and losses during 2020. The estimated future amortization expense of purchased intangible assets as of December 31, 2020, is as follows (in thousands): 2021 $ 646 2022 29 2023 29 2024 29 2025 29 Thereafter 706 $ 1,468

Balance sheet components

Balance sheet components	12 Months Ended
	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Balance sheet components	Balance sheet components Restricted Cash Restricted cash was as follows (in thousands): December 31, 2020 2019 Restricted in connection with notes payable and short-term borrowing (see Note 11) $ — $ 2,559 Restricted in connection with APAT OE asset purchase agreement — 1,999 Restricted in connection with a current legal dispute with APAT OE — 5,989 Restricted in connection with government grants received in advance 452 425 Restricted - Other 37 — Total restricted cash $ 489 $ 10,972 Accounts receivable, net Accounts receivable, net were as follows (in thousands): December 31, 2020 2019 Accounts receivable $ 45,277 $ 68,988 Trade notes receivable — 156 Allowance for doubtful accounts (45) (254) $ 45,232 $ 68,890 The table below summarizes the movement in the Company’s allowance for doubtful accounts (in thousands): Balance at December 31, 2017 $ (626) Reversal of provision for bad debt, net 428 Write-offs, net of recoveries (66) Balance at December 31, 2018 (264) Reversal of provision for bad debt, net 15 Write-offs, net of recoveries (5) Balance at December 31, 2019 (254) Reversal of provision for bad debt, net 16 Write-offs, net of recoveries 193 Balance at December 31, 2020 $ (45) Inventories Inventories were as follows (in thousands): December 31, 2020 2019 Raw materials $ 25,620 $ 19,350 Work in process 9,196 12,262 Finished goods (1) 12,085 15,318 $ 46,901 $ 46,930 (1) Included in finished goods was $1.7 million and $1.6 million of inventory at customer vendor managed inventory locations at December 31, 2020 and 2019, respectively. Prepaid expenses and other current assets Prepaid expenses and other current assets were as follows (in thousands): December 31, 2020 2019 Prepaid taxes and taxes receivable 6,137 $ 6,979 Transition services agreement receivable - APAT OE (See Note 14) 5,933 11,861 Receivables due from suppliers 4,891 4,147 Deposits and other prepaid expenses 2,417 2,512 Other receivable 795 352 $ 20,173 $ 25,851 Property, plant and equipment, net Property, plant and equipment, net were as follows (in thousands): December 31, 2020 2019 Land $ 3,367 $ 3,197 Buildings 25,310 23,624 Machinery and equipment 181,375 181,596 Furniture, fixtures, software and office equipment 20,992 10,736 Leasehold improvements 22,456 22,058 253,500 241,211 Less: Accumulated depreciation (186,735) (160,078) $ 66,765 $ 81,133 Depreciation expense was $30.6 million, $27.7 million and $29.9 million for the years ended December 31, 2020, 2019 and 2018, respectively. Accrued and other current liabilities Accrued and other current liabilities were as follows (in thousands): December 31, 2020 2019 Employee-related $ 19,656 $ 17,877 Transition services agreement payables (See Note 14) 9,708 11,765 Asset sale related contingent liabilities - APAT OE (See Note 14) — 6,664 Operating lease liabilities, current 2,128 2,086 Income and other taxes payable 1,590 2,036 Accrued warranty 1,111 712 Other accrued expenses 7,860 6,341 $ 42,053 $ 47,481 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, 2020 2019 2018 Beginning balance $ 712 $ 672 $ 1,334 Warranty accruals 1,678 782 399 Settlements (1,279) (742) (1,061) Ending balance $ 1,111 $ 712 $ 672 Other noncurrent liabilities Other noncurrent liabilities were as follows (in thousands): December 31, 2020 2019 Pension and other employee-related $ 3,844 $ 4,125 Transition services agreement payables (See Note 14) 823 — Government grant 606 1,380 Deferred income tax liabilities 501 528 *Asset retirement obligations 3,810 3,529 Other — 52 $ 9,584 $ 9,614 *Asset retirement obligations are legal obligations associated with the retirement of long-lived assets pertaining to leasehold improvements. In 2020 accretion related to the asset retirement obligations was $0.3 million.

Asset sale

Asset sale	12 Months Ended
	Dec. 31, 2020
Discontinued Operations and Disposal Groups [Abstract]
Asset sale	Asset sale NeoRussia 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 related to these operations, bringing the total amount accrued for the Rusnano payment derivative to $2.0 million. As of December 31, 2018, the Company had recorded assets with a carrying value of $3.0 million as held for sale. The balance for liabilities held for sale as of December 31, 2018 was immaterial. In April 2019, the Company completed the sale of 100% interest in the operations of NeoPhotonics Corporation, LLC, to Joint Stock Company Rusnano, a related party. In connection with the sale, the Company received $2.0 million in cash, settled the $2.0 million exit fee and recognized a gain on asset sale of $0.9 million within operating expenses during the 2019.

Restructuring and Other Related

Restructuring and Other Related Charges	12 Months Ended
	Dec. 31, 2020
Restructuring and Related Activities [Abstract]
Restructuring and Other Related Charges	Restructuring and Other Related Charges 2020 Restructuring Restructuring charges On August 17, 2020, BIS increased restrictions on Huawei and its affiliates on the Entity List related to items produced domestically and abroad that use U.S. technology or software and imposed additional requirements for items subject to Commerce export control. The Company announced on October 5, 2020, that it would manage the business without relying on and will not plan on future revenue contributions from Huawei. As a result, the Company initiated certain restructuring actions to reduce operating expenses and manufacturing costs while maintaining the Company's focus on its core capabilities, including its lasers, coherent components and solutions for data center interconnect and high speed communications networks. Under the restructuring actions, the Company estimates it will incur severance and related charges of approximately $1.1 million and is expected to be completed by the third quarter of 2021. Other related charges In light of the restrictions imposed on Huawei by the BIS in the third quarter of 2020, the Company incurred $4.1 million in accelerated depreciation charges related to Huawei specific assets, consolidation of Indium Phosphide production and certain end-of-life equipment. In addition, the Company incurred $1.9 million in inventory purchase commitment liabilities and $2.5 million in Huawei specific excess and obsolete inventories, resulting in a total inventory write-down of $4.4 million. The total restructuring and other charges for this action are estimated to be $10.9 million through 2021. Restructuring and other related charges for the year ended December 31, 2020 were as follows (in thousands): Year Ended December 31, 2020 Charges Incurred to Date Cash - restructuring charges: Severance and related costs $ 1,023 $ 1,023 Cash - other related charges: Inventory purchase commitments $ 1,913 $ 1,913 Noncash - other related charges: Accelerated depreciation $ 4,635 $ 4,635 Excess and obsolete inventories 2,522 2,522 Total other related charges $ 7,157 $ 7,157 The other cash and noncash related charges for the year ended December 31, 2020 and incurred to date totaling $1.9 million and $7.2 million, respectively, have been charged to cost of goods sold in the Company's Consolidated Statements of Operations. The restructuring charges are included in the following line items in the Company's Consolidated Statements of Operations as follows (in thousands): Year Ended December 31, 2020 Charges Incurred to Date Severance related charges: Cost of goods sold $ 867 $ 867 Restructuring charges 156 156 Total severance related charges $ 1,023 $ 1,023 A summary of the current period activity in accrued restructuring costs is as follows (in thousands): Employee Severance Others Total Restructuring obligations December 31, 2019 $ — $ — $ — Charges 981 42 1,023 Cash payments (884) — (884) Restructuring obligations December 31, 2020 $ 97 $ 42 $ 139 2017 and 2018 Restructuring The Company has completed all actions under the 2017 and 2018 restructuring plans. At December 31, 2020 and 2019, there were no restructuring obligations under the two restructuring plans. In 2017 and 2018, 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 $0.3 million in restructuring charges within operating expenses in 2019 and $0.2 million and $3.1 million in restructuring charges within cost of goods sold and operating expenses in 2018, respectively.

Debt

Debt	12 Months Ended
	Dec. 31, 2020
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, 2020 December 31, 2019 Carrying Interest Carrying Interest Long-term debt, current and non-current: Borrowing under Wells Fargo Credit Facility $ 21,030 2.01 % $ 27,329 3.72 % Mitsubishi Bank loans 7,662 1.05%-1.45% 9,255 1.04%-1.44% Mitsubishi Bank and Yamanashi Chou Bank loan 5,002 1.07 % 5,868 1.07 % Finance lease liability 189 275 Unaccreted discount and issuance costs (324) (446) Total long-term debt, net of unaccreted discount and issuance costs $ 33,559 $ 42,281 Reported as: Current portion of long-term debt $ 3,232 $ 3,044 Long-term debt, net of current portion 30,327 39,237 Total long-term debt, net of unaccreted discount and issuance costs $ 33,559 $ 42,281 The effective interest rates of the debt in the table above approximated their stated interest rates. 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 • Under the first line of credit facility with Shanghai Pudong Development Bank, the Company can borrow up to RMB 120.0 million ($18.4 million) for short-term loans at varying interest rates, or up to approximately RMB 240.0 million ($36.7 million) for bank acceptance drafts (with up to 50% compensating balance requirement). This line of credit facility expires in November 2021. • 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 ($4.6 million) for short-term loans at varying interest rates, or up to approximately RMB 60.0 million ($9.2 million) for bank acceptance drafts (with up to 50% compensating balance requirement). 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 no outstanding balance at December 31, 2020 and 2019 , respectively. As of December 31, 2019, compensating balances relating to bank acceptance drafts and letters of credit issued to suppliers and the Company's subsidiaries totaled $2.5 million. There were no such balances as of December 31, 2020. Compensating balances are classified as restricted cash on the Company’s consolidated balance sheets. Credit Facilities 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"). 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. On June 14, 2019, the Company entered into a First Amendment to the Credit Facility (the "Amended Credit Facility"). The Amendment removes Huawei from the list of “Eligible Accounts” as a basis for the Company’s borrowing while Huawei is on the U.S. Bureau of Industry and Security (“BIS”) “Entity List”. During the period of time while Huawei remains on the Entity List, the concentration limits of certain other customers are increased to partially offset the removal of Huawei. Additionally, until Huawei is no longer on the Entity List, the Company is required to maintain a temporary combination of certain defined unrestricted cash and unused borrowing capacity under the Credit Facility of at least $30.0 million in the U.S. and $40.0 million world-wide, of which at least $5.0 million shall include unused borrowing capacity. The Company was in compliance with the covenants of this Credit Facility as of December 31, 2020. As of December 31, 2020, the outstanding balance under the Credit Facility was $21.0 million and the weighted average rate under the LIBOR option was 2.01%. The remaining borrowing capacity as of December 31, 2020 was $6.5 million, of which $5.0 million is required to be maintained as unused borrowing capacity. The Company repaid $7.0 million and $10.0 million under the revolving line of credit in 2020 and 2019, respectively. In 2020, $0.7 million accrued interest were rolled into the principal amount of Wells Fargo Credit Facility . 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 ($9.7 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 8.3 million JPY until the maturity date of February 25, 2025, with a lump sum payment of the balance of 8.4 million 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 40.5 million 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 coverage ratio covenant. The Company was in compliance with the related covenants as of December 31, 2020 and 2019. Outstanding principal balance for Term Loan B and unamortized debt issuance costs were approximately 416.7 million JPY (approximately $4.0 million) and 6.9 million JPY (approximately $0.1 million), respectively, as of December 31, 2020. 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 $6.7 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 coverage ratio covenant. The Company was in compliance with these covenants as of December 31, 2020. The loan was available from March 31, 2017 to March 30, 2018 and 690 million JPY (approximately $6.7 million) under this loan was fully drawn in March 2017. Outstanding principal balance for the 2017 Mitsubishi Bank Loan and unamortized debt issuance costs were approximately 373.8 million JPY (approximately $3.6 million) and 11.2 million JPY (approximately $0.1 million), respectively, as of December 31, 2020. 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 $8.2 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, 2020. Outstanding principal balance for the Mitsubishi Bank and Yamanashi Chou Bank Loan and unamortized debt issuance costs were approximately 516.1 million JPY (approximately $5.0 million) and 15.1 million JPY (approximately $0.1 million), respectively, as of December 31, 2020. At December 31, 2020, maturities of long-term debt were as follows (in thousands): 2021 $ 3,356 2022 24,385 2023 3,261 2024 2,425 2025 456 $ 33,883

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	Leases The Company has operating leases for offices, research and development facilities and manufacturing facilities. Leases have remaining terms of less than one year to seven years, some of which include options to extend the leases and some of which may include options to terminate the leases within one year. On June 13, 2017, the Company entered into an office lease for approximately 39,000 square feet in San Jose (the “Lease”), with a commencement date of June 1, 2017. 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 $41,000, escalating annually to a maximum monthly rental rate of approximately $73,000 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 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 an initial 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, 2020 and December 31, 2019, an asset recorded in property, plant and equipment under a finance lease was immaterial. The components of lease expense were as follows (in thousands): Year Ended 2020 2019 Operating lease cost $ 3,056 $ 3,026 Variable and short-term lease cost 2,007 1,482 Total lease cost $ 5,063 $ 4,508 In 2018, The Company accounted for leases in accordance with ASC 840 and recognized rent expense on a straight-line basis over the lease period. Rent expense under the Company’s operating leases was $4.2 million in the year ended December 31, 2018. Other information related to leases was as follows (in thousands, except lease term and discount rate): Year Ended 2020 2019 Supplemental cash flow information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $3,193 $3,600 Right-of-use assets obtained in exchange for lease obligations: Operating leases $98 $136 Weighted average remaining lease term (in years) Operating leases 6.5 7.4 Weighted average discount rate Operating leases 6.5% 6.4% Future minimum lease payments under non-cancelable leases as of December 31, 2020 were as follows (in thousands): Operating Leases 2021 $ 3,144 2022 3,135 2023 3,074 2024 2,944 2025 3,021 Thereafter 5,234 Total future minimum lease payments 20,552 Less imputed interest (3,902) Total $ 16,650 Reported as of December 31, 2020: Operating Leases Accrued and other current liabilities $ 2,128 Operating lease liabilities, noncurrent 14,522 Total $ 16,650

Pension Plans

Pension Plans	12 Months Ended
	Dec. 31, 2020
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 Semiconductor Co., Ltd. ("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 the plan for the years ended December 31, 2020, 2019 and 2018 was as follows (in thousands): 2020 2019 2018 RAP RAP RAP Change in projected benefit obligation: Projected benefit obligation, beginning of period $ 4,090 $ 4,308 $ 4,616 Interest cost 4 4 4 Benefits paid (531) (276) (517) Actuarial (gain)/loss (21) — 95 Currency translation adjustment 201 54 110 Projected benefit obligation, end of period $ 3,743 $ 4,090 $ 4,308 Plan assets at calculated amount, end of period $ — $ — $ — Amounts recognized in consolidated balance sheets: Accrued and other current liabilities $ 707 $ 585 $ 257 Other noncurrent liabilities $ 3,036 $ 3,505 $ 4,051 Amount recognized in accumulated other comprehensive loss: Defined benefit pension plans adjustment $ 398 $ 378 $ 373 Accumulated benefit obligation, end of period $ 3,743 $ 4,090 $ 4,308 Net periodic pension cost associated with the plan for the years ended December 31, 2020, 2019 and 2018 included the following components (in thousands): 2020 2019 2018 RAP RAP RAP Service cost $ — $ — $ — Interest cost 4 4 4 Other — — — Curtailment/settlement (gain) loss — — — Net periodic pension costs $ 4 $ 4 $ 4 The projected and accumulated benefit obligations for the RAP were calculated as of December 31, 2020, 2019 and 2018 using a discount rate assumption of 0.1% in each of those years. Estimated future benefit payments under the RAP are as follows (in thousands): 2021 $ 642 2022 314 2023 — 2024 435 2025 376 2026 - 2030 1,349 Thereafter 627 $ 3,743 401(k) Plan

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies 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), except for the matter discussed in the following paragraph, 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 (acquired by II-VI, Inc. in September 2019) ("Finisar"), filed a complaint in the U.S. District Court for the Northern District of California, 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 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 estimate a range of possible loss. APAT Litigation and Settlement Since April 2018, APAT OE and NeoPhotonics (China) Co., Ltd. and NeoPhotonics Dongguan Co. Ltd. (collectively "NeoChina", which are both wholly-owned subsidiaries of the Company) and NeoPhotonics Corporation was involved in a series of litigations and arbitrations which arose out of the 2017 sale by NeoChina of certain low speed transceiver assets to APAT. On October 27, 2020, the parties entered into a settlement agreement to settle all claims and release all property preservation orders. In exchange for a full release of all claims by all parties, terms of the settlement agreement include the following: i) APAT OE to pay NeoChina the arbitration awards in the amount of RMB 52,014,519 (approximately $7.6 million) plus interest of RMB 6,122,150 (approximately $0.9 million) for a total amount of RMB 58,136,669 (approximately $8.5 million) and ii) NeoPhotonics Corporation to pay APAT Hong Kong, a wholly-owned subsidiary of APAT OE, $10,031,515 USD plus $500,000 USD in interest for a total payment $10,531,515 for amounts that were paid by customers to NeoPhotonics Corporation for sales of products made by APAT OE after the close of the asset purchase agreement. Under the settlement agreement, each party takes turns paying a portion of the total amounts owed until all amounts have been paid. The first payment from APAT OE to the Company occurred in November 2020. All other payments, except the final payment, are expected to be completed in Q1 2021 with the final payment by the Company to APAT expected to occur in Q1 of 2022. The settlement award of RMB 58,136,669 (approximately $8.5 million) payable by APAT OE to the Company represents repayment of the net receivables owed to the Company at the settlement date and partial recovery of previously recognized losses incurred by the Company of approximately $3.0 million primarily related to a litigation settlement loss with a vendor for committed purchases of certain production materials for which the liabilities were assumed by APAT OE in the Asset Purchase Agreement entered into with the Company in December 2016 and the legal fees incurred for the lawsuits with APAT OE during 2018, 2019 and 2020. At December 31, 2020, the amount payable by the Company to APAT OE under the settlement agreement is approximately $10.5 million, and is included in Accrued and Other Liabilities in the caption "Transition Services Agreement Payable" (See Note 8). At December 31, 2020, the amount receivable from APAT OE is approximately $5.9 million and is included in Prepaid Expenses and Other Current Assets in the caption "Transition Services Agreement Receivable" (See Note 8.) Indemnifications In the normal course of business, the Company enters into agreements that contain a variety of representations and warranties and provides 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. 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, 2020, the Company’s estimate of outstanding amounts under these purchase orders was approximately $25.8 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. 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 agreed to be paid by Rusnano consisted 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. This transaction was completed in April 2019.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2020
Stockholders' Equity Note [Abstract]
Stockholders’ Equity	Stockholders’ Equity Common stock As of December 31, 2020, the Company had reserved 8,206,682 shares of common stock for issuance under its stock plans and 1,391,002 shares of common stock for issuance under its employee stock purchase plan. In August 2019, the Company filed a prospectus supplement with SEC to issue 103,734 shares of common stock and additional shares of common stock with an aggregate offering price of up to $4.5 million to one of the Company’s vendors as a consideration for research and development services. In 2019 the Company issued common shares totaling 441,410 for a total consideration of $2.5 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, 2020 and 2019 (in thousands): December 31, December 31, Foreign currency translation adjustments $ 1,951 $ (7,641) Defined benefit pension plan adjustment, net of taxes (216) (230) $ 1,735 $ (7,871) Accumulated Deficit

Restricted net assets

Restricted net assets	12 Months Ended
	Dec. 31, 2020
Restricted Net Assets [Abstract]
Restricted net assets	Restricted net assets The Company’s consolidated subsidiaries operating in China and Japan are restricted from transferring funds or assets to its parent company in the form of cash dividends, loans or advances. As of December 31, 2020 and December 31, 2019, the Company's consolidated subsidiaries had $11.4 million and $21.1 million, respectively, of restricted net assets. This compares to the Company's consolidated net assets of $180.4 million and $160.2 million as of December 31, 2020 and December 31, 2019, respectively, which consisted of (in thousands): December 31, 2020 December 31, 2019 Cash restricted in China as a result of ongoing litigation and unfulfilled government grants $ 452 $ 10,936 China earnings restricted to fund statutory common reserves in China 10,010 9,240 Loan agreements in Japan requiring local subsidiaries to maintain minimum net asset levels 969 920 Total restricted net assets in the Company's consolidated subsidiaries $ 11,431 $ 21,096

Stock-based compensation

Stock-based compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-based compensation	Stock-based compensation Equity incentive programs 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, 2020, no stock appreciation units were outstanding. 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 terminated on April 13, 2020. 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 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, 2020, stock options to purchase and restricted stock units to convert to a total of 5,682,649 shares of common stock were outstanding under the 2010 Plan and no shares were available 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 16th of each year, with two purchase dates on May 15th and November 15th. 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, in an amount equal to the lesser of (1) 3.5% of the total number of shares of common stock outstanding on December 31st 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, 2020, the Company had 1,391,002 shares reserved for future issuance. In June 2019, the Company’s stockholders approved an amendment and restatement of the 2010 ESPP, which authorized 1,500,000 additional shares for issuance under the 2010 ESPP and eliminated the annual automatic increase provisions from the 2010 ESPP. 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, 2020, stock options to purchase and restricted stock units to convert to a total of 491,414 shares of common stock were outstanding under the 2011 Plan and no shares were available for future issuance. 2020 Equity Incentive Plan On June 2, 2020, at the 2020 Annual Meeting of Stockholders of NeoPhotonics Corporation, the Company’s stockholders approved NeoPhotonics Corporation 2020 Equity Incentive Plan (the “2020 Plan”). The Plan became effective immediately upon stockholder approval at the Annual Meeting. The aggregate number of shares of common stock reserved for issuance under the 2020 Plan will not exceed the sum of (i) 1,921,414 shares and (ii) certain shares subject to outstanding awards granted under the Company’s 2010 Equity Incentive Plan or 2011 Inducement Award Plan that may become available for issuance under the 2020 Plan, as such shares become available from time to time. As of December 31, 2020, stock options to purchase and restricted stock units to convert to a total of 246,435 shares of common stock were outstanding under the 2020 Plan and 1,786,184 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 2020 2019 2018 Weighted-average expected term (years) 6.00 6.00 6.02 Weighted-average volatility 69% 67% 65% Risk-free interest rate 0.46% 1.82%-2.27% 2.27%-2.62% Expected dividends —% —% —% Stock appreciation units Weighted-average expected term (years) 1.15 1.52 1.94 Weighted-average volatility 66% 64% 66% Risk-free interest rate 0.11%-1.60% 1.63%-2.63% 1.03%-2.81% Expected dividends —% —% —% ESPP Weighted-average expected term (years) 0.72 0.71 0.72 Weighted-average volatility 62% 71% 61% Risk-free interest rate 0.11%-0.15% 1.75%-2.44% 1.93%-2.59% 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, 2020, 2019 and 2018. Unamortized stock-based compensation costs capitalized as part of inventory were immaterial in each of the periods presented (in thousands): Years ended December 31, 2020 2019 2018 Cost of goods sold $ 2,305 $ 2,244 $ 2,596 Research and development 3,367 3,138 3,570 Sales and marketing 2,403 2,411 3,248 General and administrative 4,262 4,663 4,728 $ 12,337 $ 12,456 $ 14,142 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, 2020. The table does not include market-based or performance based RSU awards. 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, 2019 1,309,215 2,598,745 $ 5.93 3,170,981 $ 5.80 Authorized for issuance 3,619,813 — — — — Granted (2,086,620) 53,760 8.56 1,942,460 7.67 Exercised/Converted — (498,041) 4.36 (1,313,256) 6.19 Cancelled/Forfeited (1,056,224) (57,547) 10.42 (178,504) 6.48 Balance at December 31, 2020 1,786,184 2,096,917 $ 6.25 3,621,681 $ 6.63 The following table summarizes information about stock options outstanding as of December 31, 2020: 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 2,093,935 $ 6.25 4.42 $ 6,579,560 Exercisable 2,013,287 $ 6.22 4.28 $ 6,407,012 The weighted-average exercise price of stock options outstanding as of December 31, 2020 was $6.25. As of December 31, 2020, the weighted-average remaining contractual term of stock options outstanding was 4.42 years. The fair value of options vested during the years ended December 31, 2020, 2019 and 2018 was $0.9 million, $1.6 million and $2.3 million, respectively. The intrinsic value of options vested and expected to vest and exercisable as of December 31, 2019 is calculated based on the difference between the exercise price and the fair value of the Company’s common stock as of December 31, 2020. The intrinsic value of options exercised during the years ended December 31, 2020, 2019 and 2018, was $2.1 million, $1.3 million and $2.4 million, respectively. The weighted-average fair value of options granted was $5.22, $2.68 and $4.03 per share for the years ended December 31, 2020, 2019 and 2018, respectively. At December 31, 2020, there was $0.3 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 0.7 years. Included in the outstanding stock options at December 31, 2020 are 0.5 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, 2020: 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 3,173,040 $ — 1.34 $ 28,842,929 The fair value of RSUs vested during the years ended December 31, 2020, 2019 and 2018 was $8.1 million, $8.9 million and $9.8 million, respectively. The intrinsic value of RSUs vested and expected to vest as of December 31, 2020 is calculated based on the fair value of the Company’s common stock as of December 31, 2020. The intrinsic value of RSUs converted during the years ended December 31, 2020, 2019 and 2018, was $11.3 million, $4.7 million and $7.4 million, respectively. The weighted-average fair value of RSUs granted was $7.67, $4.90 and $6.83 per share for the years ended December 31, 2020, 2019 and 2018, respectively. At December 31, 2020, the Company had $15.6 million of unrecognized stock-based compensation expense for RSUs, net of estimated forfeitures, which will be recognized over the remaining weighted-average period of 2.5 years. The majority of the Company’s RSUs that were converted during the years ended December 31, 2020, 2019 and 2018 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 2020, 2019 and 2018, the Company withheld 206,065, 155,267 and 147,572 shares, respectively, and remitted cash of $1.8 million, $0.7 million and $1.0 million, respectively, to the appropriate tax authorities. Market-based Restricted Stock Unit Activity In 2019 and 2018, the Company granted 10,000 shares and 695,000 shares, respectively, 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. 30,000 and 63,500 RSU's were canceled during 2020 and 2019, respectively, no RSUs were canceled in 2018. There were no RSUs vested in 2020, 2019 and 2018. The weighted average grant-date fair value per share of market-based RSUs granted during 2019 and 2018 was approximately $4.86 and $5.82, respectively. As of December 31, 2020, the Company had $0.6 million of unrecognized stock-based compensation expense for RSUs, net of estimated forfeitures, which will be recognized over the remaining weighted-average period of 0.78 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, 2019 2018 Weighted-average volatility 66% 66% Risk-free interest rate 2.79% 2.79% Expected dividends —% —% Market-based RSUs expire seven years from the date of grant. As of December 31, 2020, the weighted average remaining contractual term for market-based RSUs is 4.6 years. Performance-based Restricted Stock Units In April 2020, the Company granted 90,400 shares of performance-based RSUs to certain employees. These RSUs will vest upon certification by the Board of Directors or the Compensation Committee that the Company has achieved at least $425 million in revenue over four consecutive fiscal quarters and the recipients remain in continuous service with the Company through such service period. No performance-based RSUs were vested or cancelled during 2020. The weighted average grant-date fair value per share of performance-based RSUs granted during 2020 was $7.73 per share Stock Appreciation Unit Activity The following table summarizes the Company’s stock appreciation unit activity during the year ended December 31, 2020: Stock Appreciation Units Weighted-Average Exercise Price Stock appreciation units outstanding as of December 31, 2019 163,471 $ 5.01 Stock appreciation units exercised (10,264) $ 3.58 Stock appreciation units canceled (3,207) $ 5.06 Stock appreciation units outstanding as of December 31, 2020 150,000 $ 5.11 The fair value of stock appreciation units vested was immaterial in 2020, 2019 and 2018. 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, 2020. Cash paid for stock appreciation units exercised was $0.1 million in 2020, 2019 and 2018, respectively. The stock appreciation units may only be settled in cash. As of December 31, 2020 and 2019, the liability for settlement of stock appreciation units was approximately $0.7 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, 2020 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 2020, the Company recorded approximately $0.1 million gain as compared to approximately $0.2 million loss in 2019, in related stock-based compensation for these stock appreciation units. Employee Stock Purchase Plan

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 U.S. operations $ (7,083) $ (21,579) $ (43,384) Non-U.S. operations 3,919 6,136 1,076 $ (3,164) $ (15,443) $ (42,308) The components of the provision for income taxes consisted of the following (in thousands): Years Ended December 31, 2020 2019 2018 Current Federal $ (39) $ (71) $ (49) State (12) (3) 36 Foreign (2,091) (1,854) (1,634) (2,142) (1,928) (1,647) Deferred Federal — — 42 Foreign 940 295 276 Total provision $ (1,202) $ (1,633) $ (1,329) The tax provision differs from the amount obtained by applying the U.S. federal statutory tax rate as follows (in thousands, except percentages): Years Ended December 31, 2020 2019 2018 Federal statutory rate 21 % 21 % 21 % Tax at federal statutory rate $ 673 $ 3,255 $ 8,869 State taxes, net of federal benefit (12) (3) 36 Permanent differences (125) 1,514 (371) Stock-based compensation (1,054) (1,014) (1,079) Change in valuation allowance (885) (5,186) (10,094) Research and development 713 932 914 Foreign rate differences (205) (531) (697) Foreign tax credit — (405) 49 Change in prior year deferred balances (302) — 1,653 Other (5) (195) (609) Total provision for income taxes $ (1,202) $ (1,633) $ (1,329) Deferred income tax assets and liabilities comprise the following (in thousands): December 31, 2020 2019 Deferred Tax Assets: Net operating loss carryforwards $ 53,906 $ 54,339 Federal and state credits 31,927 30,111 Reserves, accruals and other 13,339 14,132 Fixed assets and intangibles 3,297 2,783 Total deferred tax assets 102,469 101,365 Valuation allowance (94,017) (92,149) Total deferred tax assets, net of valuation allowance 8,452 9,216 Less deferred tax liabilities: Acquired intangibles (288) (283) Property, plant and equipment (3,217) (4,663) Right-of-use lease assets (2,796) (3,124) Net deferred tax assets $ 2,151 $ 1,146 Reported as: Long term deferred tax assets, included within other long-term assets $ 2,652 $ 1,674 Long term deferred income tax liabilities, included within noncurrent liabilities (501) (528) Net deferred tax assets $ 2,151 $ 1,146 The net valuation allowance increased by $1.9 million in 2020 and increased by $0.7 million in 2019. There was no material change to the valuation allowance in 2020. 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, 2020. 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. As of December 31, 2020, the Company had federal and state net operating loss, or NOL, carryforwards of approximately $289.4 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, 2020, the Company also had federal and state research and development tax credit carryovers of $11.3 million and $20.2 million, respectively. The federal credits will begin to expire in 2021 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 2023 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. The Company maintains its position for undistributed foreign earnings to be indefinite and does not provide for outside basis differences under the indefinite reinvestment assertion of ASC 740-30. Accordingly, the Company does not anticipate the need to provide for additional taxes for basis differences or withholding taxes on remitted foreign earnings in the immediate future. At December 31, 2020, the Company’s gross unrecognized tax benefits were approximately $20.5 million, of which none would impact the effective tax rate if recognized. A substantial portion of these unrecognized tax benefits could be subject to 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, 2017 $ 25,539 Net changes in tax positions in the period 657 Balance at December 31, 2018 26,196 Net changes in tax positions in the period (5,544) Balance at December 31, 2019 20,652 Net changes in tax positions in current year (106) Balance at December 31, 2020 $ 20,546

Segment and geographic informat

Segment and geographic information	12 Months Ended
	Dec. 31, 2020
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 2020, 2019 and 2018, the Company operated in one reportable segment. Through 2020, 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, 2020 2019 Property, plant and equipment, net: China $ 19,144 $ 19,230 United States 21,734 26,068 Japan 21,409 25,772 Rest of world 4,478 10,063 Total $ 66,765 $ 81,133

Selected Quarterly Financial Da

Selected Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2020
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, 2020 and 2019: Year ended December 31, 2020 First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share value) Revenues $ 97,401 $ 103,171 $ 102,398 $ 68,193 Gross profit 29,726 33,502 24,404 15,450 Net income (loss) 6,307 5,725 (4,903) (11,495) Basic net income (loss) per share $ 0.13 $ 0.12 $ (0.10) $ (0.23) Diluted net income (loss) per share $ 0.12 $ 0.11 $ (0.10) $ (0.23) Weighted averages shares used to compute basic net income (loss) per share 48,615 49,077 49,936 50,256 Weighted averages shares used to compute diluted net income (loss) per share 50,617 51,661 49,936 50,256 Year ended December 31, 2019 First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share value) Revenues $ 79,366 $ 81,690 $ 92,392 $ 103,356 Gross profit 15,737 15,675 26,199 31,202 Net income (loss) (14,091) (7,326) 2,272 2,069 Basic net income (loss) per share $ (0.30) $ (0.16) $ 0.05 $ 0.04 Diluted net income (loss) per share (0.30) (0.16) 0.05 0.04 Weighted averages shares used to compute basic net income (loss) per share 46,414 46,754 47,666 48,358 Weighted averages shares used to compute diluted net income (loss) per share 46,414 46,754 48,615 50,238

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Business and organization	Business and organization
Certain Significant Risks and Uncertainties	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; successful and timely completion of product design efforts; the ability of the Company to sell its new products into new market segments; trade restrictions by the United States against the Company's customers in China, as well as potential retaliatory trade actions taken by China; the loss of any of its larger customers; restrictions on the Company's ability to sell to foreign customers due to additional U.S. or new China trade laws, regulations and requirements; disruptions of the supply chain of components needed for its products; ability to obtain additional financing; inability to meet certain debt covenants; fundamental changes in the technology underlying the Company’s products; the hiring, training and retention of key employees; and new product design introductions by competitors. The inputs into the Company’s judgments and estimates consider the economic implications of the Covid-19 pandemic as the Company knows them, on its critical and significant accounting estimates. The extent to which the Covid-19 pandemic may impact its business will depend on future developments, which are highly uncertain, such as the duration of the outbreak, travel restrictions, governmental mandates issued to mitigate the spread of the disease, business closures, economic disruptions, and the effectiveness of actions taken to contain and treat the virus. Accordingly, future adverse developments with respect to the Covid-19 pandemic may have a negative impact on its sales, supply chain and results of operations. The inputs into the Company's judgments and estimates also consider the Department of Commerce Entities List restrictions on Huawei Technologies effective September 2020 for the Company and expected loss of business from Huawei Technologies. See also Note 10.
Consolidation	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.
Use of estimates	Use of estimates The preparation of financial statements in accordance with 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 and recoverability of long-lived assets; valuation allowances for deferred tax assets; valuation of excess and obsolete inventories; warranty reserves; litigation accrual 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
Restricted cash	Restricted cash
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.
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.
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.
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.
Goodwill	Goodwill
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 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. Due to the Department of Commerce Entities List restrictions effective September 2020 and expected loss of business from Huawei, the Company performed a recoverability test in the third and fourth quarters of 2020 and determined there was no impairment of long-lived assets.
Leases	Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in operating lease right-of-use ("ROU") assets, other current liabilities and operating lease liabilities on the Company's consolidated balance sheet. Finance leases are included in property, plant and equipment, current portion of long-term debt and long-term debt, net of current portion on the consolidated balance sheets. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. As most of our leases do not provide an implicit rate, the Company uses an estimate of its incremental borrowing rate based on observed market data and other information available at the lease commencement date. The operating lease ROU assets also include any lease payments made and exclude lease incentives. Lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. The Company does not record leases on the consolidated balance sheet with a term of one year or less. The Company does not separate lease and non-lease components but rather account for each separate component as a single lease component for all underlying classes of assets. Variable lease payments are expensed as incurred and are not included within the operating lease ROU asset and lease liability calculation. Variable lease payments primarily include reimbursements of costs incurred by lessors for common area maintenance and utilities. Lease expense for minimum operating lease payments is recognized on a straight-line basis over the lease term.
Product warranties	Product warranties one
Research and development	Research and development
Advertising costs	Advertising costs
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.
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.
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. 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 $2.2 million loss in 2018 relating to its foreign currency contracts within other income, net. Net foreign exchange gain (loss) was ($5.9) million, $0.2 million, and $1.4 million in 2020, 2019, and 2018, 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
Net income (loss) per share	Net income (loss) per shareBasic 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.
Reclassifications	Reclassifications Certain prior year amounts have been reclassified to conform to the current year presentation.
Accounting standards update recently adopted and not yet effective	Accounting standards update recently adopted In January 2017, the Financial Accounting Standards Board ("FASB") issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (“ASU 2017-04”). 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. In November 2019, the FASB issued ASU 2019-10, according to which, the new standard is effective for smaller reporting companies (“SRC”) as defined by the SEC, for fiscal years beginning after December 15, 2022 including interim periods within those fiscal years. The Company early adopted ASU 2017-04 guidance on January 1, 2020. The adoption of this standard had no material impact on the Company’s consolidated financial statements and related disclosures. In February 2016, the Financial Accounting Standards Board ("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 using the modified retrospective transition method. In July 2018, the FASB issued ASU 2018- 11, Leases (ASC 842): Targeted Improvements. The update provides an optional transition method that allows entities to change the date of initial application to the beginning of the period of adoption. The Company adopted the guidance on January 1, 2019 under the optional transition method. Certain optional practical expedients are allowed. The Company elected the package of practical expedients permitted under the transition guidance, which allowed the Company to carryforward historical lease classification, assessment on whether a contract was or contains a lease, and initial direct costs for any leases that existed prior to January 1, 2019. The Company also elected to combine lease and non-lease components and to keep leases with an initial term of 12 months or less off the consolidated balance sheet. As a result of adopting Topic 842 on January 1, 2019, the Company recognized operating lease right-of-use assets of $17.3 million and corresponding operating lease liabilities of $20.8 million from existing leases on the Company's consolidated balance sheet. Refer to Note 12 for further details. The adoption of Topic 842 had no impact on the Company's consolidated statement of operations or consolidated statement of cash flows. Recent accounting standards update not yet effective 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. In November 2019, the FASB issued ASU 2019-10, according to which, the new standard is effective for smaller reporting companies (“SRC”) as defined by the SEC, for fiscal years beginning after December 15, 2022 including interim periods within those fiscal years. The Company is in the process of evaluating the impact and timing of the adoption on its consolidated financial statements and related disclosures. In December 2019, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes. This guidance is effective for fiscal years beginning after December 15, 2020, with early adoption permitted. The Company will adopt this ASU in the first quarter of 2021 and is currently evaluating the impact of this ASU on the consolidated financial statements and related disclosures.
Revenue recognition	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. The Company's standard payment terms range from 30 to 90 days. Shipping and handling costs are included in the cost of goods sold. The Company presents revenue net of sales taxes and any similar assessments. The Company’s performance obligations relate to contracts with a duration of less than one year. The Company elected to apply the practical expedient provided in Accounting Standard Codification Topic 606, “Revenue from Contracts with Customers” and, therefore, is not required to disclose the aggregate amount of the transaction price allocated to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period. Contract Costs The Company recognizes the incremental direct costs of obtaining a contract, which consist of sales commissions, when control over the products they relate to transfers to the customer. Applying the practical expedient, the Company recognizes commissions as expense when incurred, as the amortization period of the commission asset the Company would have otherwise recognized is less than one year.

Summary of significant accoun_3

Summary of significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020, 2019 and 2018 were as follows: Years Ended December 31, 2020 2019 2018 Percent of revenue from customers accounting for 10% or more of total revenue: Huawei Technologies Co., Ltd 40 % 41 % 46 % Ciena Corporation 17 % 29 % 24 % Acacia Communications, Inc. 10 % 5 % 2 % Percent of revenue from top five customers 79 % 84 % 87 %
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 December 31, 2020 2019 Land $ 3,367 $ 3,197 Buildings 25,310 23,624 Machinery and equipment 181,375 181,596 Furniture, fixtures, software and office equipment 20,992 10,736 Leasehold improvements 22,456 22,058 253,500 241,211 Less: Accumulated depreciation (186,735) (160,078) $ 66,765 $ 81,133

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Summary of Revenue by Product Group and Geographical Region	The following presents revenue by product group (in thousands): Years Ended December 31, 2020 2019 2018 High Speed Products $ 340,015 $ 323,804 $ 275,803 Network Products and Solutions 31,148 33,000 46,737 Total revenue $ 371,163 $ 356,804 $ 322,540 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, designated shipping points are often in China or elsewhere in Asia (in thousands): Years Ended December 31, 2020 2019 2018 China $ 191,990 $ 186,157 $ 187,277 Thailand 70,709 55,385 37,357 Mexico 35,549 74,077 54,771 Rest of world 72,915 41,185 43,135 Total revenue $ 371,163 $ 356,804 $ 322,540

Cash, cash equivalents, short_2

Cash, cash equivalents, short-term investments and restricted cash (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Cash and cash equivalents: Cash $ 95,117 70,467 Cash equivalents — — Cash and cash equivalents $ 95,117 $ 70,467 Short-term investments $ 27,669 $ 7,638 Restricted cash $ 489 $ 10,972 December 31, 2020 December 31, 2019 Cash and cash equivalents $ 95,117 $ 70,467 Restricted cash 489 10,972 Total cash, cash equivalents and restricted cash shown in the consolidated statement of cash flows $ 95,606 $ 81,439
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 short-term investments in marketable securities designated as available-for-sale (in thousands): As of December 31, 2020 As of December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Marketable securities: Money market funds 27,669 — — 27,669 7,638 — — 7,638 Total $ 27,669 $ — $ — $ 27,669 $ 7,638 $ — $ — $ 7,638 Reported as: Short-term investments 27,669 — — 27,669 7,638 — — 7,638 Total $ 27,669 $ — $ — $ 27,669 $ 7,638 $ — $ — $ 7,638
Maturities of Marketable Securities	As of December 31, 2020 and 2019, maturities of marketable securities were as follows (in thousands): December 31, 2020 December 31, 2019 Less than 1 year $ 27,669 $ 7,638 Due in 1 to 2 years — — Due in 3 to 5 years — — Total $ 27,669 $ 7,638

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 December 31, 2019 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash equivalents and short-term investments: Money market funds $ 27,669 $ — $ — $ 27,669 $ 7,638 $ — $ — $ 7,638 Total $ 27,669 $ — $ — $ 27,669 $ 7,638 $ — $ — $ 7,638 Mutual funds held in Rabbi Trust, recorded in other long-term assets $ 810 $ — $ — $ 810 $ 616 $ — $ — $ 616

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 Numerator: Net loss (4,366) $ (17,076) $ (43,637) Denominator: Weighted average shares used to compute per share amount: Basic 49,474 47,304 45,144 Dilutive effect of equity awards — — — Diluted 49,474 47,304 45,144 Basic net loss per share $ (0.09) $ (0.36) $ (0.97) Diluted net loss per share $ (0.09) $ (0.36) $ (0.97)
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, 2020 2019 2018 Employee stock options 2,097 2,599 3,203 Restricted stock units 3,621 3,171 2,486 Market-based restricted stock units 612 641 695 Performance-based restricted stock units 90 — — Employee stock purchase plan 358 298 414 6,778 6,709 6,798

Purchased intangible assets (Ta

Purchased intangible assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Purchased Intangible Assets	Purchased intangible assets consist of the following (in thousands): December 31, 2020 December 31, 2019 Gross Accumulated Net Gross Accumulated Net Technology and patents $ 37,637 $ (37,021) $ 616 $ 36,880 $ (35,555) $ 1,325 Customer relationships 15,487 (15,487) — 15,089 (15,089) — Leasehold interest 1,304 (452) 852 1,222 (396) 826 $ 54,428 $ (52,960) $ 1,468 $ 53,191 $ (51,040) $ 2,151
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, 2020 2019 2018 Cost of goods sold $ 737 $ 737 $ 756 Operating expenses — 119 475 Total $ 737 $ 856 $ 1,231
Estimated Future Amortization Expense of Purchased Intangible Assets	The estimated future amortization expense of purchased intangible assets as of December 31, 2020, is as follows (in thousands): 2021 $ 646 2022 29 2023 29 2024 29 2025 29 Thereafter 706 $ 1,468

Balance sheet components (Table

Balance sheet components (Tables)	12 Months Ended
	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Restricted Cash	Restricted cash was as follows (in thousands): December 31, 2020 2019 Restricted in connection with notes payable and short-term borrowing (see Note 11) $ — $ 2,559 Restricted in connection with APAT OE asset purchase agreement — 1,999 Restricted in connection with a current legal dispute with APAT OE — 5,989 Restricted in connection with government grants received in advance 452 425 Restricted - Other 37 — Total restricted cash $ 489 $ 10,972 December 31, 2020 December 31, 2019 Cash restricted in China as a result of ongoing litigation and unfulfilled government grants $ 452 $ 10,936 China earnings restricted to fund statutory common reserves in China 10,010 9,240 Loan agreements in Japan requiring local subsidiaries to maintain minimum net asset levels 969 920 Total restricted net assets in the Company's consolidated subsidiaries $ 11,431 $ 21,096
Accounts Receivable, Net	Accounts receivable, net were as follows (in thousands): December 31, 2020 2019 Accounts receivable $ 45,277 $ 68,988 Trade notes receivable — 156 Allowance for doubtful accounts (45) (254) $ 45,232 $ 68,890
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, 2017 $ (626) Reversal of provision for bad debt, net 428 Write-offs, net of recoveries (66) Balance at December 31, 2018 (264) Reversal of provision for bad debt, net 15 Write-offs, net of recoveries (5) Balance at December 31, 2019 (254) Reversal of provision for bad debt, net 16 Write-offs, net of recoveries 193 Balance at December 31, 2020 $ (45)
Inventories	Inventories were as follows (in thousands): December 31, 2020 2019 Raw materials $ 25,620 $ 19,350 Work in process 9,196 12,262 Finished goods (1) 12,085 15,318 $ 46,901 $ 46,930
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets were as follows (in thousands): December 31, 2020 2019 Prepaid taxes and taxes receivable 6,137 $ 6,979 Transition services agreement receivable - APAT OE (See Note 14) 5,933 11,861 Receivables due from suppliers 4,891 4,147 Deposits and other prepaid expenses 2,417 2,512 Other receivable 795 352 $ 20,173 $ 25,851
Property, Plant and Equipment, Net	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 December 31, 2020 2019 Land $ 3,367 $ 3,197 Buildings 25,310 23,624 Machinery and equipment 181,375 181,596 Furniture, fixtures, software and office equipment 20,992 10,736 Leasehold improvements 22,456 22,058 253,500 241,211 Less: Accumulated depreciation (186,735) (160,078) $ 66,765 $ 81,133
Accrued and Other Current Liabilities	Accrued and other current liabilities were as follows (in thousands): December 31, 2020 2019 Employee-related $ 19,656 $ 17,877 Transition services agreement payables (See Note 14) 9,708 11,765 Asset sale related contingent liabilities - APAT OE (See Note 14) — 6,664 Operating lease liabilities, current 2,128 2,086 Income and other taxes payable 1,590 2,036 Accrued warranty 1,111 712 Other accrued expenses 7,860 6,341 $ 42,053 $ 47,481
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, 2020 2019 2018 Beginning balance $ 712 $ 672 $ 1,334 Warranty accruals 1,678 782 399 Settlements (1,279) (742) (1,061) Ending balance $ 1,111 $ 712 $ 672
Other Noncurrent Liabilities	Other noncurrent liabilities were as follows (in thousands): December 31, 2020 2019 Pension and other employee-related $ 3,844 $ 4,125 Transition services agreement payables (See Note 14) 823 — Government grant 606 1,380 Deferred income tax liabilities 501 528 *Asset retirement obligations 3,810 3,529 Other — 52 $ 9,584 $ 9,614 *Asset retirement obligations are legal obligations associated with the retirement of long-lived assets pertaining to leasehold improvements. In 2020 accretion related to the asset retirement obligations was $0.3 million.

Restructuring and Other Relat_2

Restructuring and Other Related Charges (Tables)	12 Months Ended
	Dec. 31, 2020
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	Restructuring and other related charges for the year ended December 31, 2020 were as follows (in thousands): Year Ended December 31, 2020 Charges Incurred to Date Cash - restructuring charges: Severance and related costs $ 1,023 $ 1,023 Cash - other related charges: Inventory purchase commitments $ 1,913 $ 1,913 Noncash - other related charges: Accelerated depreciation $ 4,635 $ 4,635 Excess and obsolete inventories 2,522 2,522 Total other related charges $ 7,157 $ 7,157
Schedule of Restructuring Reserve by Type	A summary of the current period activity in accrued restructuring costs is as follows (in thousands): Employee Severance Others Total Restructuring obligations December 31, 2019 $ — $ — $ — Charges 981 42 1,023 Cash payments (884) — (884) Restructuring obligations December 31, 2020 $ 97 $ 42 $ 139

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 December 31, 2019 Carrying Interest Carrying Interest Long-term debt, current and non-current: Borrowing under Wells Fargo Credit Facility $ 21,030 2.01 % $ 27,329 3.72 % Mitsubishi Bank loans 7,662 1.05%-1.45% 9,255 1.04%-1.44% Mitsubishi Bank and Yamanashi Chou Bank loan 5,002 1.07 % 5,868 1.07 % Finance lease liability 189 275 Unaccreted discount and issuance costs (324) (446) Total long-term debt, net of unaccreted discount and issuance costs $ 33,559 $ 42,281 Reported as: Current portion of long-term debt $ 3,232 $ 3,044 Long-term debt, net of current portion 30,327 39,237 Total long-term debt, net of unaccreted discount and issuance costs $ 33,559 $ 42,281
Maturities of Long-term Debt	At December 31, 2020, maturities of long-term debt were as follows (in thousands): 2021 $ 3,356 2022 24,385 2023 3,261 2024 2,425 2025 456 $ 33,883

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of lease, cost	The components of lease expense were as follows (in thousands): Year Ended 2020 2019 Operating lease cost $ 3,056 $ 3,026 Variable and short-term lease cost 2,007 1,482 Total lease cost $ 5,063 $ 4,508 In 2018, The Company accounted for leases in accordance with ASC 840 and recognized rent expense on a straight-line basis over the lease period. Rent expense under the Company’s operating leases was $4.2 million in the year ended December 31, 2018. Other information related to leases was as follows (in thousands, except lease term and discount rate): Year Ended 2020 2019 Supplemental cash flow information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $3,193 $3,600 Right-of-use assets obtained in exchange for lease obligations: Operating leases $98 $136 Weighted average remaining lease term (in years) Operating leases 6.5 7.4 Weighted average discount rate Operating leases 6.5% 6.4%
Schedule of future minimum lease payments under non-cancellable leases	Future minimum lease payments under non-cancelable leases as of December 31, 2020 were as follows (in thousands): Operating Leases 2021 $ 3,144 2022 3,135 2023 3,074 2024 2,944 2025 3,021 Thereafter 5,234 Total future minimum lease payments 20,552 Less imputed interest (3,902) Total $ 16,650
Schedule of operating leases	Reported as of December 31, 2020: Operating Leases Accrued and other current liabilities $ 2,128 Operating lease liabilities, noncurrent 14,522 Total $ 16,650

Pension Plans (Tables)

Pension Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Funded Status Plans	The funded status of the plan for the years ended December 31, 2020, 2019 and 2018 was as follows (in thousands): 2020 2019 2018 RAP RAP RAP Change in projected benefit obligation: Projected benefit obligation, beginning of period $ 4,090 $ 4,308 $ 4,616 Interest cost 4 4 4 Benefits paid (531) (276) (517) Actuarial (gain)/loss (21) — 95 Currency translation adjustment 201 54 110 Projected benefit obligation, end of period $ 3,743 $ 4,090 $ 4,308 Plan assets at calculated amount, end of period $ — $ — $ — Amounts recognized in consolidated balance sheets: Accrued and other current liabilities $ 707 $ 585 $ 257 Other noncurrent liabilities $ 3,036 $ 3,505 $ 4,051 Amount recognized in accumulated other comprehensive loss: Defined benefit pension plans adjustment $ 398 $ 378 $ 373 Accumulated benefit obligation, end of period $ 3,743 $ 4,090 $ 4,308
Periodic Pension Cost	Net periodic pension cost associated with the plan for the years ended December 31, 2020, 2019 and 2018 included the following components (in thousands): 2020 2019 2018 RAP RAP RAP Service cost $ — $ — $ — Interest cost 4 4 4 Other — — — Curtailment/settlement (gain) loss — — — Net periodic pension costs $ 4 $ 4 $ 4
Estimated Future Benefit Payments Under Plans	Estimated future benefit payments under the RAP are as follows (in thousands): 2021 $ 642 2022 314 2023 — 2024 435 2025 376 2026 - 2030 1,349 Thereafter 627 $ 3,743

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 and 2019 (in thousands): December 31, December 31, Foreign currency translation adjustments $ 1,951 $ (7,641) Defined benefit pension plan adjustment, net of taxes (216) (230) $ 1,735 $ (7,871)

Restricted net assets (Tables)

Restricted net assets (Tables)	12 Months Ended
	Dec. 31, 2020
Restricted Net Assets [Abstract]
Schedule of restrictions on net assets	Restricted cash was as follows (in thousands): December 31, 2020 2019 Restricted in connection with notes payable and short-term borrowing (see Note 11) $ — $ 2,559 Restricted in connection with APAT OE asset purchase agreement — 1,999 Restricted in connection with a current legal dispute with APAT OE — 5,989 Restricted in connection with government grants received in advance 452 425 Restricted - Other 37 — Total restricted cash $ 489 $ 10,972 December 31, 2020 December 31, 2019 Cash restricted in China as a result of ongoing litigation and unfulfilled government grants $ 452 $ 10,936 China earnings restricted to fund statutory common reserves in China 10,010 9,240 Loan agreements in Japan requiring local subsidiaries to maintain minimum net asset levels 969 920 Total restricted net assets in the Company's consolidated subsidiaries $ 11,431 $ 21,096

Stock-based compensation (Table

Stock-based compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [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 2020 2019 2018 Weighted-average expected term (years) 6.00 6.00 6.02 Weighted-average volatility 69% 67% 65% Risk-free interest rate 0.46% 1.82%-2.27% 2.27%-2.62% Expected dividends —% —% —% Stock appreciation units Weighted-average expected term (years) 1.15 1.52 1.94 Weighted-average volatility 66% 64% 66% Risk-free interest rate 0.11%-1.60% 1.63%-2.63% 1.03%-2.81% Expected dividends —% —% —% ESPP Weighted-average expected term (years) 0.72 0.71 0.72 Weighted-average volatility 62% 71% 61% Risk-free interest rate 0.11%-0.15% 1.75%-2.44% 1.93%-2.59% 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, 2020 2019 2018 Cost of goods sold $ 2,305 $ 2,244 $ 2,596 Research and development 3,367 3,138 3,570 Sales and marketing 2,403 2,411 3,248 General and administrative 4,262 4,663 4,728 $ 12,337 $ 12,456 $ 14,142
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, 2020. The table does not include market-based or performance based RSU awards. 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, 2019 1,309,215 2,598,745 $ 5.93 3,170,981 $ 5.80 Authorized for issuance 3,619,813 — — — — Granted (2,086,620) 53,760 8.56 1,942,460 7.67 Exercised/Converted — (498,041) 4.36 (1,313,256) 6.19 Cancelled/Forfeited (1,056,224) (57,547) 10.42 (178,504) 6.48 Balance at December 31, 2020 1,786,184 2,096,917 $ 6.25 3,621,681 $ 6.63
Summary of Information about Stock Options Outstanding	The following table summarizes information about stock options outstanding as of December 31, 2020: 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 2,093,935 $ 6.25 4.42 $ 6,579,560 Exercisable 2,013,287 $ 6.22 4.28 $ 6,407,012
Summary of Information about Restricted Stock Units Outstanding	The following table summarizes information about RSUs outstanding as of December 31, 2020: 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 3,173,040 $ — 1.34 $ 28,842,929
Schedule of Estimated Fair Value of Certain Stock-Based Awards using Black-Scholes-Merton Valuation Model	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, 2019 2018 Weighted-average volatility 66% 66% Risk-free interest rate 2.79% 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, 2020: Stock Appreciation Units Weighted-Average Exercise Price Stock appreciation units outstanding as of December 31, 2019 163,471 $ 5.01 Stock appreciation units exercised (10,264) $ 3.58 Stock appreciation units canceled (3,207) $ 5.06 Stock appreciation units outstanding as of December 31, 2020 150,000 $ 5.11

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 U.S. operations $ (7,083) $ (21,579) $ (43,384) Non-U.S. operations 3,919 6,136 1,076 $ (3,164) $ (15,443) $ (42,308)
Components of Provision for Income Taxes	The components of the provision for income taxes consisted of the following (in thousands): Years Ended December 31, 2020 2019 2018 Current Federal $ (39) $ (71) $ (49) State (12) (3) 36 Foreign (2,091) (1,854) (1,634) (2,142) (1,928) (1,647) Deferred Federal — — 42 Foreign 940 295 276 Total provision $ (1,202) $ (1,633) $ (1,329)
Difference in Provision for Income Taxes from Amount Obtained by Applying U.S. Federal Statutory Rate	The tax provision differs from the amount obtained by applying the U.S. federal statutory tax rate as follows (in thousands, except percentages): Years Ended December 31, 2020 2019 2018 Federal statutory rate 21 % 21 % 21 % Tax at federal statutory rate $ 673 $ 3,255 $ 8,869 State taxes, net of federal benefit (12) (3) 36 Permanent differences (125) 1,514 (371) Stock-based compensation (1,054) (1,014) (1,079) Change in valuation allowance (885) (5,186) (10,094) Research and development 713 932 914 Foreign rate differences (205) (531) (697) Foreign tax credit — (405) 49 Change in prior year deferred balances (302) — 1,653 Other (5) (195) (609) Total provision for income taxes $ (1,202) $ (1,633) $ (1,329)
Components of Deferred Income Tax Assets and Liabilities	Deferred income tax assets and liabilities comprise the following (in thousands): December 31, 2020 2019 Deferred Tax Assets: Net operating loss carryforwards $ 53,906 $ 54,339 Federal and state credits 31,927 30,111 Reserves, accruals and other 13,339 14,132 Fixed assets and intangibles 3,297 2,783 Total deferred tax assets 102,469 101,365 Valuation allowance (94,017) (92,149) Total deferred tax assets, net of valuation allowance 8,452 9,216 Less deferred tax liabilities: Acquired intangibles (288) (283) Property, plant and equipment (3,217) (4,663) Right-of-use lease assets (2,796) (3,124) Net deferred tax assets $ 2,151 $ 1,146 Reported as: Long term deferred tax assets, included within other long-term assets $ 2,652 $ 1,674 Long term deferred income tax liabilities, included within noncurrent liabilities (501) (528) Net deferred tax assets $ 2,151 $ 1,146
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, 2017 $ 25,539 Net changes in tax positions in the period 657 Balance at December 31, 2018 26,196 Net changes in tax positions in the period (5,544) Balance at December 31, 2019 20,652 Net changes in tax positions in current year (106) Balance at December 31, 2020 $ 20,546

Segment and geographic inform_2

Segment and geographic information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Revenue and Long-Lived Assets By Geographical Region	The following tables set forth the Company’s asset information by geographic region (in thousands): As of December 31, 2020 2019 Property, plant and equipment, net: China $ 19,144 $ 19,230 United States 21,734 26,068 Japan 21,409 25,772 Rest of world 4,478 10,063 Total $ 66,765 $ 81,133

Selected Quarterly Financial _2

Selected Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 and 2019: Year ended December 31, 2020 First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share value) Revenues $ 97,401 $ 103,171 $ 102,398 $ 68,193 Gross profit 29,726 33,502 24,404 15,450 Net income (loss) 6,307 5,725 (4,903) (11,495) Basic net income (loss) per share $ 0.13 $ 0.12 $ (0.10) $ (0.23) Diluted net income (loss) per share $ 0.12 $ 0.11 $ (0.10) $ (0.23) Weighted averages shares used to compute basic net income (loss) per share 48,615 49,077 49,936 50,256 Weighted averages shares used to compute diluted net income (loss) per share 50,617 51,661 49,936 50,256 Year ended December 31, 2019 First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share value) Revenues $ 79,366 $ 81,690 $ 92,392 $ 103,356 Gross profit 15,737 15,675 26,199 31,202 Net income (loss) (14,091) (7,326) 2,272 2,069 Basic net income (loss) per share $ (0.30) $ (0.16) $ 0.05 $ 0.04 Diluted net income (loss) per share (0.30) (0.16) 0.05 0.04 Weighted averages shares used to compute basic net income (loss) per share 46,414 46,754 47,666 48,358 Weighted averages shares used to compute diluted net income (loss) per share 46,414 46,754 48,615 50,238

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Huawei Technologies Co., Ltd
Concentration Risk [Line Items]
Percentage of concentration of credit risk	40.00%	41.00%	46.00%
Ciena Corporation
Concentration Risk [Line Items]
Percentage of concentration of credit risk	17.00%	29.00%	24.00%
Acacia Communications, Inc.
Concentration Risk [Line Items]
Percentage of concentration of credit risk	10.00%	5.00%	2.00%
Top Five Customers
Concentration Risk [Line Items]
Percentage of concentration of credit risk	79.00%	84.00%	87.00%

Summary of significant accoun_5

Summary of significant accounting policies - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 489,000	$ 10,972,000
Goodwill impairment charges	0	0	$ 0
Asset impairment charges	$ 0	0	1,000,000
Conversion of stock, shares issued ratio	1
Loss on foreign currency contracts			2,200,000
Net gains (losses) resulting from foreign exchange transactions	$ (5,900,000)	200,000	$ 1,400,000
Operating lease right-of-use assets	13,823,000	$ 15,603,000		$ 17,300,000
Operating lease, liability	$ 16,650,000			$ 20,800,000
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 | Three customers | Accounts Receivable
Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration of credit risk	65.00%
Customer Concentration Risk | Two customers | Accounts Receivable
Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration of credit risk		56.00%

Summary of significant accoun_6

Summary of significant accounting policies - Estimated Useful Lives of Property, Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2020
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 - Narrative (Details)

Revenue - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Timing of payment	The Company's standard payment terms range from 30 to 90 days.
Deferred Revenue	$ 0	$ 0
Contract assets	$ 0	$ 0

Revenue - Revenue by Product Gr

Revenue - Revenue by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 68,193	$ 102,398	$ 103,171	$ 97,401	$ 103,356	$ 92,392	$ 81,690	$ 79,366	$ 371,163	$ 356,804	$ 322,540
High Speed Products
Disaggregation of Revenue [Line Items]
Total revenue									340,015	323,804	275,803
Network Products and Solutions
Disaggregation of Revenue [Line Items]
Total revenue									$ 31,148	$ 33,000	$ 46,737

Revenue - Revenue From External

Revenue - Revenue From External Customers By Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 68,193	$ 102,398	$ 103,171	$ 97,401	$ 103,356	$ 92,392	$ 81,690	$ 79,366	$ 371,163	$ 356,804	$ 322,540
China
Disaggregation of Revenue [Line Items]
Total revenue									191,990	186,157	187,277
Thailand
Disaggregation of Revenue [Line Items]
Total revenue									70,709	55,385	37,357
Mexico
Disaggregation of Revenue [Line Items]
Total revenue									35,549	74,077	54,771
Rest of world
Disaggregation of Revenue [Line Items]
Total revenue									$ 72,915	$ 41,185	$ 43,135

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, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and cash equivalents:
Cash	$ 95,117	$ 70,467
Cash equivalents	0	0
Cash and cash equivalents	95,117	70,467
Short-term investments	27,669	7,638
Restricted cash	489	10,972
Total cash, cash equivalents and restricted cash shown in the consolidated statement of cash flows	$ 95,606	$ 81,439	$ 69,238	$ 81,564

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, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 27,669	$ 7,638
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	27,669	7,638
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	27,669	7,638
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	27,669	7,638
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	27,669	7,638
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	$ 27,669	$ 7,638

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, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Less than 1 year	$ 27,669	$ 7,638
Due in 1 to 2 years	0	0
Due in 3 to 5 years	0	0
Total	$ 27,669	$ 7,638

Cash, cash equivalents, short_6

Cash, cash equivalents, short-term investments and restricted cash - Narrative (Details)	12 Months Ended
	Dec. 31, 2020USD ($)investment	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Cash and Cash Equivalents [Abstract]
Debt securities, available-for-sale, impairment losses | $	$ 0	$ 0	$ 0
Debt securities, unrealized loss position, 12 months or longer | investment	0

Fair value measurements - Asset

Fair value measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	$ 27,669	$ 7,638
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	27,669	7,638
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	0	0
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	27,669	7,638
Money market funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	27,669	7,638
Money market funds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	0	0
Money market funds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets	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	810	616
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	810	616
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	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	$ 0	$ 0

Fair value measurements - Narra

Fair value measurements - Narrative (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets (liabilities)	$ 0	$ 0

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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss	$ (11,495)	$ (4,903)	$ 5,725	$ 6,307	$ 2,069	$ 2,272	$ (7,326)	$ (14,091)	$ (4,366)	$ (17,076)	$ (43,637)
Denominator:
Weighted average shares used to compute per share amount, basic (in shares)	50,256	49,936	49,077	48,615	48,358	47,666	46,754	46,414	49,474	47,304	45,144
Dilutive effect of equity awards (in shares)									0	0	0
Weighted average shares used to compute diluted net (loss) income (in shares)	50,256	49,936	51,661	50,617	50,238	48,615	46,754	46,414	49,474	47,304	45,144
Basic net loss per share (USD per share)	$ (0.23)	$ (0.10)	$ 0.12	$ 0.13	$ 0.04	$ 0.05	$ (0.16)	$ (0.30)	$ (0.09)	$ (0.36)	$ (0.97)
Diluted net loss per share (USD per share)	$ (0.23)	$ (0.10)	$ 0.11	$ 0.12	$ 0.04	$ 0.05	$ (0.16)	$ (0.30)	$ (0.09)	$ (0.36)	$ (0.97)

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	6,778	6,709	6,798
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)	2,097	2,599	3,203
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)	3,621	3,171	2,486
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)	612	641	695
Performance-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)	90	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)	358	298	414

Purchased intangible assets - C

Purchased intangible assets - Components (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Assets	$ 54,428	$ 53,191
Accumulated Amortization	(52,960)	(51,040)
Net Assets	1,468	2,151
Technology and patents
Finite-Lived Intangible Assets [Line Items]
Gross Assets	37,637	36,880
Accumulated Amortization	(37,021)	(35,555)
Net Assets	616	1,325
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Assets	15,487	15,089
Accumulated Amortization	(15,487)	(15,089)
Net Assets	0	0
Leasehold interest
Finite-Lived Intangible Assets [Line Items]
Gross Assets	1,304	1,222
Accumulated Amortization	(452)	(396)
Net Assets	$ 852	$ 826

Purchased intangible assets - A

Purchased intangible assets - Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Cost of goods sold	$ 737	$ 737	$ 756
Operating expenses	0	119	475
Total	$ 737	$ 856	$ 1,231

Purchased intangible assets - E

Purchased intangible assets - Estimated Future Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
2021	$ 646
2022	29
2023	29
2024	29
2025	29
Thereafter	706
Net Assets	$ 1,468	$ 2,151

Balance sheet components - Rest

Balance sheet components - Restricted Cash and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	$ 489	$ 10,972
APAT OE Legal Dispute
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	0	5,989
Advances, Government Grants Received
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	452	425
Restricted - Other
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	37	0
Restricted in connection with asset purchase agreement
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	0	1,999
Restricted in connection with notes payable and short-term borrowing
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	$ 0	$ 2,559

Balance sheet components - Acco

Balance sheet components - Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accounts receivable	$ 45,277	$ 68,988
Trade notes receivable	0	156
Allowance for doubtful accounts	(45)	(254)
Accounts receivable, net ,total	$ 45,232	$ 68,890

Balance sheet components - Allo

Balance sheet components - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reversal of provision for bad debt, net	$ 16	$ 13	$ (61)
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	(254)	(264)	(626)
Reversal of provision for bad debt, net	16	15	428
Write-offs, net of recoveries	193	(5)	(66)
Ending Balance	$ (45)	$ (254)	$ (264)

Balance sheet components - Inve

Balance sheet components - Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Raw materials	$ 25,620	$ 19,350
Work in process	9,196	12,262
Finished goods	12,085	15,318
Inventories	46,901	46,930
Finished goods, at vendor managed inventory locations	$ 1,700	$ 1,600

Balance sheet components - Prep

Balance sheet components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Prepaid taxes and taxes receivable	$ 6,137	$ 6,979
Transition services agreement receivable - APAT OE (See Note 14)	5,933	11,861
Receivables due from suppliers	4,891	4,147
Deposits and other prepaid expenses	2,417	2,512
Other receivable	795	352
Prepaid expenses and other current assets	$ 20,173	$ 25,851

Balance sheet components - Prop

Balance sheet components - Property, Plant and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 253,500	$ 241,211
Less: Accumulated depreciation	(186,735)	(160,078)
Property, plant and equipment, net	66,765	81,133
Depreciation expense	30,600	27,700	$ 29,900
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment	3,367	3,197
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment	25,310	23,624
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	181,375	181,596
Furniture, fixtures, software and office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	20,992	10,736
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 22,456	$ 22,058

Balance sheet components - Accr

Balance sheet components - Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Employee-related	$ 19,656	$ 17,877
Transition services agreement payables (See Note 14)	9,708	11,765
Asset sale related contingent liabilities - APAT OE (See Note 14.)	0	6,664
Operating lease liabilities, current	2,128	2,086
Income and other taxes payable	1,590	2,036
Accrued warranty	1,111	712
Other accrued expenses	7,860	6,341
Accrued and other current liabilities	$ 42,053	$ 47,481

Balance sheet components - Ac_2

Balance sheet components - Accrued Warranty (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]
Beginning balance	$ 712	$ 672	$ 1,334
Warranty accruals	1,678	782	399
Settlements	(1,279)	(742)	(1,061)
Ending balance	$ 1,111	$ 712	$ 672

Balance sheet components - Othe

Balance sheet components - Other Noncurrent Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Pension and other employee-related	$ 3,844	$ 4,125
Transition services agreement payables (See Note 14)	823	0
Government grant	606	1,380
Deferred income tax liabilities	501	528
Asset retirement obligations	3,810	3,529
Other	0	52
Other noncurrent liabilities	9,584	$ 9,614
Accretion of asset retirement obligations	$ 300

Asset sale (Details)

Asset sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restructuring charges	$ 156	$ 261	$ 3,135
Gain within operating income	$ 1,044	903	(200)
Joint Stock Company Rusnano
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accrued payment derivative, amount			$ 2,000
NeoPhotonics Corporation, LLC | Sale of assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent of interest to be disposed			100.00%
Restructuring charges			$ 1,600
Assets held for sale			$ 3,000
Ownership interest disposed				100.00%
Consideration received pursuant to asset purchase agreement		2,000
Exit fee settlements		$ 2,000

Restructuring and Other Relat_3

Restructuring and Other Related Charges - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation	$ 4,100	$ 4,635
Inventory related charges	4,400
Noncash related charges		7,157
Restructuring charges		1,023	$ 300
Cost of goods sold
Restructuring Cost and Reserve [Line Items]
Noncash related charges		7,200
Restructuring charges				$ 200
Operating expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 3,100
Employee Severance
Restructuring Cost and Reserve [Line Items]
Estimated costs remaining		1,100
Expected costs		10,900
Cash related charges		1,023
Restructuring charges		981
Inventory purchase commitments
Restructuring Cost and Reserve [Line Items]
Inventory related charges	1,900
Cash related charges		1,913
Inventory purchase commitments | Cost of goods sold
Restructuring Cost and Reserve [Line Items]
Cash related charges		$ 1,900
Excess and obsolete inventories
Restructuring Cost and Reserve [Line Items]
Inventory related charges	$ 2,500

Restructuring and Other Relat_4

Restructuring and Other Related Charges - Restructuring Related Activities (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Other noncash related charges:
Accelerated depreciation	$ 4,100	$ 4,635
Inventory related charges	4,400
Total other related charges		7,157
Severance and related costs
Cash related restructuring charges:
Cash related charges		1,023
Inventory purchase commitments
Cash related restructuring charges:
Cash related charges		1,913
Other noncash related charges:
Inventory related charges	$ 1,900
Excess and obsolete inventory
Other noncash related charges:
Inventory related charges		$ 2,522

Restructuring and Other Relat_5

Restructuring and Other Related Charges - Company's Consolidated Statements of Operations (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Restructuring Cost and Reserve [Line Items]
Total severance related charges	$ 1,023
Cost of goods sold
Restructuring Cost and Reserve [Line Items]
Total severance related charges	867
Restructuring Charges
Restructuring Cost and Reserve [Line Items]
Total severance related charges	$ 156

Restructuring and Other Relat_6

Restructuring and Other Related Charges - current period activity in accrued restructuring costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2019	$ 0
Charges	1,023	$ 300
Cash payments	(884)
Restructuring obligations December 31, 2020	139	0
Employee Severance
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2019	0
Charges	981
Cash payments	(884)
Restructuring obligations December 31, 2020	97	0
Others
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2019	0
Charges	42
Cash payments	0
Restructuring obligations December 31, 2020	$ 42	$ 0

Debt - Components of Debt, Obli

Debt - Components of Debt, Obligations, Weighted Average Interest Rate (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Finance lease liability	$ 189	$ 275
Unaccreted discount and issuance costs	(324)	(446)
Total long-term debt, net of unaccreted discount and issuance costs	33,559	42,281
Current portion of long-term debt	3,232	3,044
Long-term debt, net of current portion	30,327	39,237
Line of Credit | Wells Fargo Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 21,030	$ 27,329
Interest Rate	2.01%	3.72%
Mitsubishi Bank loans
Debt Instrument [Line Items]
Long-term debt, gross	$ 7,662	$ 9,255
Mitsubishi Bank loans | Minimum
Debt Instrument [Line Items]
Interest Rate	1.05%	1.04%
Mitsubishi Bank loans | Maximum
Debt Instrument [Line Items]
Interest Rate	1.45%	1.44%
Notes Payable to Banks | Mitsubishi Bank Loans And Yamanashi Chou Bank Loans
Debt Instrument [Line Items]
Long-term debt, gross	$ 5,002	$ 5,868
Interest Rate	1.07%	1.07%

Debt - Notes payable and Short-

Debt - Notes payable and Short-term Borrowing (Details)	12 Months Ended
	Dec. 31, 2020CNY (¥)debt_instrument	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Restricted in connection with notes payable and short-term borrowing | Second Line Of Credit, Expires July 2019 | Subsidiary in China
Debt Instrument [Line Items]
Current borrowing capacity	¥ 30,000,000	$ 4,600,000
Bankers Acceptance
Debt Instrument [Line Items]
Restricted cash and investments, current		0	$ 2,500,000
Bankers Acceptance | Subsidiary in China
Debt Instrument [Line Items]
Outstanding balance of line of credit facilities		0	$ 0
Bankers Acceptance | Second Line Of Credit, Expires July 2019 | Subsidiary in China
Debt Instrument [Line Items]
Line of credit maximum borrowing capacity	¥ 60,000,000	9,200,000
Percentage of compensating balance requirement for bank acceptance drafts	50.00%
China | First Credit Facility Expires June 2016
Debt Instrument [Line Items]
Percentage of compensating balance requirement for bank acceptance drafts	50.00%
China | Restricted in connection with notes payable and short-term borrowing
Debt Instrument [Line Items]
Number of credit facilities | debt_instrument	2
China | Restricted in connection with notes payable and short-term borrowing | First Credit Facility Expires June 2016
Debt Instrument [Line Items]
Current borrowing capacity	¥ 120,000,000	18,400,000
China | Bankers Acceptance | First Credit Facility Expires June 2016
Debt Instrument [Line Items]
Line of credit maximum borrowing capacity	¥ 240,000,000	$ 36,700,000
China | Minimum | Restricted in connection with notes payable and short-term borrowing
Debt Instrument [Line Items]
Debt instrument term	3 months
China | Maximum | Restricted in connection with notes payable and short-term borrowing
Debt Instrument [Line Items]
Debt instrument term	6 months

Debt - Credit Facilities (Detai

Debt - Credit Facilities (Details) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 14, 2019
Line of Credit Facility [Line Items]
Repayment of notes payable		$ 0	$ 4,774,000	$ 3,732,000
Accrued interest rolled into principal amount		700,000
Wells Fargo Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Line of credit maximum borrowing capacity	$ 50,000,000
Cash balance available for borrowing	100.00%
Cash balance max borrowing	$ 15,000,000
Line of credit facility, increase limit	25,000,000
Amount outstanding on line of credit	30,000,000
Repayment of notes payable	$ 20,000,000
Commitment fee	0.25%
Line of credit facility, maximum indebtedness under debt covenant	$ 20,000,000
Unused borrowing capacity	$ 5,000,000				$ 5,000,000
Outstanding balance of line of credit facilities		$ 21,000,000
Interest Rate		2.01%	3.72%
Line of credit remaining borrowing capacity		$ 6,500,000
Required amount to be maintained as unused borrowing capacity		5,000,000
Repayments of lines of credit		$ 7,000,000	$ 10,000,000
Wells Fargo Credit Facility | Line of Credit | United States
Line of Credit Facility [Line Items]
Liquidity requirements under line of credit facility					30,000,000
Wells Fargo Credit Facility | Line of Credit | Non-US
Line of Credit Facility [Line Items]
Liquidity requirements under line of credit facility					$ 40,000,000
Wells Fargo Credit Facility | Line of Credit | Minimum
Line of Credit Facility [Line Items]
Revolver accounts receivable	80.00%
Wells Fargo Credit Facility | Line of Credit | Minimum | Credit Facility Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread	1.50%
Wells Fargo Credit Facility | Line of Credit | Minimum | Prime Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread	0.50%
Wells Fargo Credit Facility | Line of Credit | Maximum
Line of Credit Facility [Line Items]
Revolver accounts receivable	85.00%
Wells Fargo Credit Facility | Line of Credit | Maximum | Credit Facility Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread	1.75%
Wells Fargo Credit Facility | Line of Credit | Maximum | Prime Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread	0.75%

Debt - Mitsubishi Bank Loans (D

Debt - Mitsubishi Bank Loans (Details) $ in Thousands	Feb. 25, 2015JPY (¥)	Apr. 30, 2018	Jan. 31, 2018USD ($)	Jan. 31, 2018JPY (¥)	Mar. 31, 2017USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2020JPY (¥)	Dec. 31, 2019USD ($)	Mar. 31, 2017JPY (¥)	Feb. 25, 2015USD ($)	Feb. 25, 2015JPY (¥)
Debt Instrument [Line Items]
Long-term debt | $						$ 33,559		$ 42,281
Term Loan A | Notes Payable to Banks
Debt Instrument [Line Items]
Debt, aggregate principal amount										$ 4,400	¥ 500,000,000
Repayments of lines of credit			$ 4,400	¥ 500,000,000
Term Loan B | Notes Payable to Banks
Debt Instrument [Line Items]
Debt, aggregate principal amount										9,700	1,000,000,000
Debt, periodic principal payments	¥ 8,300,000
Debt, lump sum payment on the maturity date	¥ 8,400,000
Term Loan B | Notes Payable to Banks | TIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread	1.40%
Mitsubishi Bank Loans | Notes Payable to Banks
Debt Instrument [Line Items]
Debt issuance costs										$ 400	¥ 40,500,000
Mitsubishi Bank Loans | Notes Payable to Banks | TIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread	1.40%
Mitsubishi Bank Loan 2015 | Notes Payable to Banks
Debt Instrument [Line Items]
Long-term debt						4,000	¥ 416,700,000
Unamortized debt issuance costs						100	6,900,000
Mitsubishi Bank Loan 2017 | Notes Payable to Banks
Debt Instrument [Line Items]
Debt, aggregate principal amount					$ 6,700				¥ 690,000,000
Long-term debt						3,600	373,800,000
Unamortized debt issuance costs						$ 100	¥ 11,200,000
Debt instrument term		72 months
Amount outstanding on line of credit					$ 6,700				¥ 690,000,000
Mitsubishi Bank Loan 2017 | Notes Payable to Banks | TIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread					1.00%

Debt - Mitsubishi Bank and Yama

Debt - Mitsubishi Bank and Yamanashi Chou Bank loan (Details) $ in Thousands	1 Months Ended
	Jan. 31, 2018USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2020JPY (¥)	Dec. 31, 2019USD ($)	Jan. 31, 2018JPY (¥)
Debt Instrument [Line Items]
Long-term debt		$ 33,559		$ 42,281
Term Loan C | Mitsubishi Bank and The Yamanashi Chou Ban, Ltd.
Debt Instrument [Line Items]
Line of credit maximum borrowing capacity	$ 8,200				¥ 850,000,000
Debt instrument term	82 months
Long-term debt		5,000	¥ 516,100,000
Unamortized debt issuance costs		$ 100	¥ 15,100,000
Term Loan C | Mitsubishi Bank and The Yamanashi Chou Ban, Ltd. | TIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread	1.00%

Debt - Maturities of Long-Term

Debt - Maturities of Long-Term debt (Details) $ in Thousands	Dec. 31, 2020USD ($)
Debt Disclosure [Abstract]
2021	$ 3,356
2022	24,385
2023	3,261
2024	2,425
2025	456
Long Term Debt	$ 33,883

Leases - Narrative (Details)

Leases - Narrative (Details) ft² in Thousands, $ in Thousands	Jun. 13, 2017USD ($)ft²	Sep. 30, 2016USD ($)ft²	Dec. 31, 2020USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Termination period			1 year
Expected lease restoration charges			$ 3,810		$ 3,529
Operating leases, rent expense				$ 4,200
Office Building
Lessee, Lease, Description [Line Items]
Net rentable area | ft²	39
Office lease term, months	123 months
Monthly rental rate	$ 41
Expected lease restoration charges	700
Office Building and Laboratory
Lessee, Lease, Description [Line Items]
Office lease term, months		129 months
Expected lease restoration charges		$ 3,100
Area of office lease | ft²		64
Office lease, monthly rental rate		$ 144
Lease, period free of charge		9 months
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term			1 year
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term			7 years
Maximum | Office Building
Lessee, Lease, Description [Line Items]
Monthly rental rate	$ 73
Maximum | Office Building and Laboratory
Lessee, Lease, Description [Line Items]
Office lease, monthly rental rate		$ 194

Leases - Lease Cost (Details)

Leases - Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 3,056	$ 3,026
Variable and short-term lease cost	2,007	1,482
Total lease cost	$ 5,063	$ 4,508

Leases - Cash Flows (Details)

Leases - Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 3,193	$ 3,600
Right-of-use assets obtained in exchange for lease obligations:
Right-of-use assets obtained in exchange for lease obligations, Operating leases	$ 98	$ 136
Weighted average remaining lease term (in years)
Weighted average remaining lease term, Operating leases	6 years 6 months	7 years 4 months 24 days
Weighted average discount rate
Weighted average discount rate, Operating leases	6.50%	6.40%

Leases - Leases, Liability, Mat

Leases - Leases, Liability, Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2019
Operating Leases
2021	$ 3,144
2022	3,135
2023	3,074
2024	2,944
2025	3,021
Thereafter	5,234
Total future minimum lease payments	20,552
Less imputed interest	(3,902)
Total	$ 16,650	$ 20,800

Leases - Balance Sheet Informat

Leases - Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Leases [Abstract]
Accrued and other current liabilities	$ 2,128	$ 2,086
Operating lease liabilities, noncurrent	14,522	$ 16,543
Total	$ 16,650		$ 20,800
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	nptn:AccruedAndOtherLiabilitiesCurrent	nptn:AccruedAndOtherLiabilitiesCurrent

Pension Plans - Narrative (Deta

Pension Plans - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2014USD ($)	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
Cost of goods sold	268,081	$ 267,991	256,367
Operating expenses	$ 99,516	$ 103,355	$ 107,831
Discount rate	0.10%	0.10%	0.10%
Reclassification out of Accumulated Other Comprehensive Income
Defined Benefit Plan Disclosure [Line Items]
Cost of goods 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, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in projected benefit obligation:
Projected benefit obligation, beginning of period	$ 4,090	$ 4,308	$ 4,616
Interest cost	4	4	4
Benefits paid	(531)	(276)	(517)
Actuarial (gain)/loss	(21)	0	95
Currency translation adjustment	201	54	110
Projected benefit obligation, end of period	3,743	4,090	4,308
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchase, Sale, and Settlement [Abstract]
Plan assets at fair value, beginning of period		0
Plan assets at fair value, end of period	0		0
Amounts recognized in consolidated balance sheets:
Accrued and other current liabilities	707	585	257
Other noncurrent liabilities	3,036	3,505	4,051
Amount recognized in accumulated other comprehensive loss:
Defined benefit pension plans adjustment	398	378	373
Accumulated benefit obligation, end of period	$ 3,743	$ 4,090	$ 4,308

Pension Plans - Periodic Pensio

Pension Plans - Periodic Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Service cost	$ 0	$ 0	$ 0
Interest cost	4	4	4
Other	0	0	0
Curtailment/settlement (gain) loss	0	0	0
Net periodic pension costs	$ 4	$ 4	$ 4

Pension Plans - Estimated Futur

Pension Plans - Estimated Future Benefit Payments Under Plans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
2021	$ 642
2022	314
2023	0
2024	435
2025	376
2026 - 2030	1,349
Thereafter	627
Defined benefit plan, benefit obligation	$ 3,743	$ 4,090	$ 4,308	$ 4,616

Pension Plans - 401 (k) Plan (D

Pension Plans - 401 (k) Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Matching contributions to 401(k) plan	$ 0.4	$ 0.5	$ 0.4

Commitments and contingencies (

Commitments and contingencies (Details)	Oct. 27, 2020USD ($)	Oct. 27, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2012USD ($)
Loss Contingencies [Line Items]
Total amount received (paid)			$ 2,988,000	$ 0	$ (2,645,000)
Total outstanding purchase obligations			25,800,000
Embedded Derivative Financial Instruments | Maximum
Loss Contingencies [Line Items]
Other non-current liability						$ 5,000,000
Performance Guarantee | Private Placement
Loss Contingencies [Line Items]
Other non-current liability							$ 30,000,000
Rusnano Group | NeoPhotonics Corporation, LLC | Sale
Loss Contingencies [Line Items]
Ownership to be disposed					100.00%
Consideration received pursuant to asset purchase agreement					$ 3,000,000
Penalty payment cancellation					$ 1,000,000
APAT Arbitration | APAT OE
Loss Contingencies [Line Items]
Paid by other party	$ 8,500,000	¥ 58,136,669
Total amount received (paid)	3,000,000
Receivable due from litigation settlement			5,900,000
Payable due to litigation settlement			$ 10,500,000
APAT Arbitration | APAT Hong Kong
Loss Contingencies [Line Items]
Interest received (paid)	(500,000)
Total amount received (paid)	(10,531,515)
Damages awarded	10,031,515
APAT Arbitration | NeoChina | APAT OE
Loss Contingencies [Line Items]
Paid by other party	7,600,000	52,014,519
Interest received (paid)	$ 900,000	¥ 6,122,150

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock, Resale Registration Statement, and Follow-on Public Offering (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Aug. 31, 2019
Class of Stock [Line Items]
Stock issued during period (in shares)		441,410
Stock issued during period		$ 2.5
Retained earnings subject to restriction	$ 10	$ 9.2
Minimum
Class of Stock [Line Items]
Accumulated profits	10.00%	10.00%
Vendor
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)			103,734
Common stock, capital shares reserved for future issuance			$ 4.5
Employee stock options
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	8,206,682
Employee stock purchase plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	1,391,002

Stockholders' Equity - Accumula

Stockholders' Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ 180,407	$ 160,206	$ 160,240	$ 194,451
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	1,951	(7,641)
Defined benefit pension plan adjustment, net of taxes
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(216)	(230)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ 1,735	$ (7,871)	$ (7,126)	$ 398

Restricted net assets (Details)

Restricted net assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted net assets in the Company's consolidated subsidiaries	$ 11,431	$ 21,096
Consolidated net assets	180,400	160,200
Cash restricted in China as a result of ongoing litigation and unfulfilled government grants
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted net assets in the Company's consolidated subsidiaries	452	10,936
China earnings restricted to fund statutory common reserves in China
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted net assets in the Company's consolidated subsidiaries	10,010	9,240
Loan agreements in Japan requiring local subsidiaries to maintain minimum net asset levels
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted net assets in the Company's consolidated subsidiaries	$ 969	$ 920

Stock-based compensation - Narr

Stock-based compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Apr. 30, 2020	Jan. 31, 2012	Sep. 30, 2011	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 02, 2020	Jun. 30, 2019	Feb. 28, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average exercise price of stock options outstanding (USD per share)				$ 6.25
Weighted-average remaining contractual term of stock options outstanding				4 years 5 months 1 day
Remitted cash to appropriate tax authorities				$ 1,751	$ 733	$ 954
Stock Appreciation Units (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised				$ 100	100	100
Number of days for stock price to be traded above mentioned price				20 days
Minimum closing stock price (USD per share)				$ 15
Share-based compensation expense (gain)				$ (100)	200
Stock grants vested value				$ 0	$ 0	0
Options to purchase shares, outstanding (in shares)				150,000	163,471
Employee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant (in shares)				1,786,184	1,309,215
Authorized for issuance (in shares)				3,619,813
Fair value of options vested				$ 900	$ 1,600	2,300
Intrinsic value of options exercised				$ 2,100	$ 1,300	$ 2,400
Weighted-average fair value of options granted (USD per share)				$ 5.22	$ 2.68	$ 4.03
Unrecognized stock-based compensation expense				$ 300
Remaining weighted-average period				8 months 12 days
Options to purchase shares, outstanding (in shares)				2,096,917	2,598,745
Stock Option and Restricted Stock Unit Activity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units (in shares)				500,000
Weighted-average fair value granted (USD per share)								$ 4.72
Number of days for stock price to be traded above mentioned price				20 days
Minimum closing stock price (USD per share)				$ 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)									$ 1.65
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)				3,621,681	3,170,981
Unrecognized stock-based compensation expense				$ 15,600
Remaining weighted-average period				2 years 6 months
Restricted stock units (in shares)				1,942,460
Weighted-average fair value granted (USD per share)				$ 7.67	$ 4.90	$ 6.83
Stock grants vested value				$ 8,100	$ 8,900	$ 9,800
Aggregate intrinsic value, vested				$ 11,300	$ 4,700	$ 7,400
Common stock withheld shares (in shares)				206,065	155,267	147,572
Remitted cash to appropriate tax authorities				$ 1,800	$ 700	$ 1,000
Vested (in shares)				1,313,256
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				9 months 10 days
Restricted stock units (in shares)					10,000	695,000
Weighted-average fair value granted (USD per share)					$ 4.86	$ 5.82
Canceled during period (in shares)				30,000	63,500	0
Vested (in shares)				0	0	0
Unrecognized stock-based compensation expense				$ 600
Remaining contractual term				4 years 7 months 6 days
Performance-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant (in shares)	90,400
Weighted-average fair value granted (USD per share)				$ 7.73
Revenue over four fiscal quarters	$ 425,000
Stock Appreciation Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Liability for settlement				$ 700	$ 800
Options to purchase shares, outstanding (in shares)				200,000
2007 Stock Appreciation Grants Plan | Stock Appreciation Units (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)				0
2010 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)				5,682,649
Awards expiration period from date of grant				10 years
Maximum aggregate number of shares of common stock that may be issued (in shares)				8,000,000									865,420
Number of shares of common stock outstanding increase percentage		3.50%
Shares available for future grant (in shares)				0
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]
Maximum aggregate number of shares of common stock that may be issued (in shares)				600,000							1,500,000	342,568
Number of shares of common stock outstanding increase percentage		3.50%
Shares available for future grant (in shares)				1,391,002
Offering period				12 months
2011 Inducement Award Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)				491,414
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
Shares available for future grant (in shares)				0
Authorized for issuance (in shares)								100,000
2020 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)				246,435
Maximum aggregate number of shares of common stock that may be issued (in shares)										1,921,414
Shares available for future grant (in shares)				1,786,184

Stock-based compensation - Assu

Stock-based compensation - Assumptions (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected term (years)	6 years	6 years	6 years 7 days
Weighted-average volatility	69.00%	67.00%	65.00%
Risk-free interest rate	46.00%
Risk-free interest rate Minimum		1.82%	2.27%
Risk-free interest rate Maximum		2.27%	2.62%
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 1 month 24 days	1 year 6 months 7 days	1 year 11 months 8 days
Weighted-average volatility	66.00%	64.00%	66.00%
Risk-free interest rate Minimum	0.11%	1.63%	1.03%
Risk-free interest rate Maximum	1.60%	2.63%	2.81%
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 15 days	8 months 19 days
Weighted-average volatility	62.00%	71.00%	61.00%
Risk-free interest rate Minimum	0.11%	1.75%	1.93%
Risk-free interest rate Maximum	0.15%	2.44%	2.59%
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%	66.00%
Risk-free interest rate	2.79%	2.79%
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, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation	$ 12,337	$ 12,456	$ 14,142
Cost of goods sold
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation	2,305	2,244	2,596
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation	3,367	3,138	3,570
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation	2,403	2,411	3,248
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation	$ 4,262	$ 4,663	$ 4,728

Stock-based compensation - Stoc

Stock-based compensation - Stock Options and RSUs (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee stock options
Shares Available for Grant
Beginning Balance (in shares)	1,309,215
Authorized for issuance (in shares)	3,619,813
Granted (in shares)	(2,086,620)
Exercised/Converted (in shares)	0
Cancelled/Forfeited (in shares)	(1,056,224)
Ending Balance (in shares)	1,786,184	1,309,215
Number of Shares
Beginning Balance (in shares)	2,598,745
Authorized for issuance (in shares)	0
Granted (in shares)	53,760
Exercised/Converted (in shares)	(498,041)
Cancelled/Forfeited (in shares)	(57,547)
Ending Balance (in shares)	2,096,917	2,598,745
Weighted Average Exercise Price
Beginning Balance (USD per share)	$ 5.93
Authorized for issuance (in shares)	0
Granted (USD per share)	8.56
Exercised/Converted (USD per share)	4.36
Cancelled/Forfeited (USD per share)	10.42
Ending Balance (USD per share)	$ 6.25	$ 5.93
Restricted stock units
Number of Shares
Beginning Balance (in shares)	3,170,981
Authorized for issuance (in shares)	0
Granted (in shares)	1,942,460
Exercised/Converted (in shares)	(1,313,256)
Cancelled/Forfeited (in shares)	(178,504)
Ending Balance (in shares)	3,621,681	3,170,981
Weighted Average Grant Date Fair Value
Beginning Balance (USD per share)	$ 5.80
Authorized for issuance (in shares)	0
Granted (USD per share)	7.67	$ 4.90	$ 6.83
Exercised/Converted (USD per share)	6.19
Cancelled/Forfeited (USD per share)	6.48
Ending Balance (USD per share)	$ 6.63	$ 5.80

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, 2020USD ($)$ / sharesshares
Number of Shares
Vested and expected to vest (in shares) | shares	2,093,935
Exercisable (in shares) | shares	2,013,287
Weighted Average Exercise Price
Vested and expected to vest (USD per share) | $ / shares	$ 6.25
Exercisable (USD per share) | $ / shares	$ 6.22
Weighted Average Remaining Contractual Term (Years)
Vested and expected to vest	4 years 5 months 1 day
Exercisable	4 years 3 months 10 days
Aggregate Intrinsic Value
Vested and expected to vest | $	$ 6,579,560
Exercisable | $	$ 6,407,012

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, 2020USD ($)$ / sharesshares
Number of Shares
Vested and expected to vest (in shares) | shares	3,173,040
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 4 months 2 days
Aggregate Intrinsic Value
Vested and expected to vest | $	$ 28,842,929

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, 2020$ / sharesshares
Stock Appreciation Units
Beginning Balance (in shares) | shares	163,471
Exercised/Converted (in shares) | shares	(10,264)
Canceled (in shares) | shares	(3,207)
Ending Balance (in shares) | shares	150,000
Weighted-Average Exercise Price
Beginning Balance (USD per share) | $ / shares	$ 5.01
Exercised/Converted (USD per share) | $ / shares	3.58
Canceled (USD per share) | $ / shares	5.06
Ending Balance (USD per share) | $ / shares	$ 5.11

Stock-based compensation - Empl

Stock-based compensation - Employee Stock Purchase Plan (Details) - Employee stock purchase plan $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock under employee stock purchase plan (in shares) | shares	326,209
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, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S. operations	$ (7,083)	$ (21,579)	$ (43,384)
Non-U.S. operations	3,919	6,136	1,076
Loss before income taxes	$ (3,164)	$ (15,443)	$ (42,308)

Income taxes - Components of Pr

Income taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current
Federal	$ (39)	$ (71)	$ (49)
State	(12)	(3)	36
Foreign	(2,091)	(1,854)	(1,634)
Provision for income tax, current	(2,142)	(1,928)	(1,647)
Deferred
Federal	0	0	42
Foreign	940	295	276
Total provision	$ (1,202)	$ (1,633)	$ (1,329)

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory rate	21.00%	21.00%	21.00%
Tax at federal statutory rate	$ 673	$ 3,255	$ 8,869
State taxes, net of federal benefit	(12)	(3)	36
Permanent differences	(125)	1,514	(371)
Stock-based compensation	(1,054)	(1,014)	(1,079)
Change in valuation allowance	(885)	(5,186)	(10,094)
Research and development	713	932	914
Foreign rate differences	(205)	(531)	(697)
Foreign tax credit	0	(405)	49
Change in prior year deferred balances	(302)	0	1,653
Other	(5)	(195)	(609)
Total provision	$ (1,202)	$ (1,633)	$ (1,329)

Income taxes - Components of De

Income taxes - Components of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets:
Net operating loss carryforwards	$ 53,906	$ 54,339
Federal and state credits	31,927	30,111
Reserves, accruals and other	13,339	14,132
Fixed assets and intangibles	3,297	2,783
Total deferred tax assets	102,469	101,365
Valuation allowance	(94,017)	(92,149)
Total deferred tax assets, net of valuation allowance	8,452	9,216
Less deferred tax liabilities:
Acquired intangibles	(288)	(283)
Property, plant and equipment	(3,217)	(4,663)
Right-of-use lease assets	(2,796)	(3,124)
Net deferred tax assets	2,151	1,146
Reported as:
Long term deferred tax assets, included within other long-term assets	2,652	1,674
Long term deferred income tax liabilities, included within noncurrent liabilities	(501)	(528)
Net deferred tax assets	$ 2,151	$ 1,146

Income taxes - Narrative (Detai

Income taxes - Narrative (Details) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Examination [Line Items]
Valuation allowance, increase (decrease)	$ 1,900,000	$ 700,000
Accumulated deficit balance for intra-entity transfer of asset	(180,407,000)	(160,206,000)	$ (160,240,000)	$ (194,451,000)
Unrecognized tax benefits	20,546,000	20,652,000	26,196,000	25,539,000
Unrecognized tax benefits that would impact the effective tax rate	0
Unrecognized tax benefits, income tax penalties and interest expense	0
Domestic Tax Authority
Income Tax Examination [Line Items]
Operating loss carryforwards	289,400,000
Domestic Tax Authority | Research Tax Credit Carryforward
Income Tax Examination [Line Items]
Tax credit carryforward	11,300,000
State and Local Jurisdiction
Income Tax Examination [Line Items]
Operating loss carryforwards	52,000,000
State and Local Jurisdiction | Research Tax Credit Carryforward
Income Tax Examination [Line Items]
Tax credit carryforward	20,200,000
Foreign Tax Authority | Research Tax Credit Carryforward
Income Tax Examination [Line Items]
Tax credit carryforward	10,500,000
Accumulated deficit
Income Tax Examination [Line Items]
Accumulated deficit balance for intra-entity transfer of asset	$ 418,914,000	$ 414,548,000	$ 397,472,000	352,011,000
Revision of Prior Period, Accounting Standards Update, Adjustment
Income Tax Examination [Line Items]
Accumulated deficit balance for intra-entity transfer of asset				1,824,000
Revision of Prior Period, Accounting Standards Update, Adjustment | Accumulated deficit
Income Tax Examination [Line Items]
Accumulated deficit balance for intra-entity transfer of asset				$ 1,824,000

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 20,652	$ 26,196	$ 25,539
Net changes in tax positions in the period			657
Net changes in tax positions in current year	(106)	(5,544)
Ending Balance	$ 20,546	$ 20,652	$ 26,196

Segment and geographic Inform_3

Segment and geographic Information - Narrative (Details) - segment	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
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, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 66,765	$ 81,133
China
Segment Reporting Information [Line Items]
Property, plant and equipment, net	19,144	19,230
United States
Segment Reporting Information [Line Items]
Property, plant and equipment, net	21,734	26,068
Japan
Segment Reporting Information [Line Items]
Property, plant and equipment, net	21,409	25,772
Rest of world
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 4,478	$ 10,063

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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Revenue	$ 68,193	$ 102,398	$ 103,171	$ 97,401	$ 103,356	$ 92,392	$ 81,690	$ 79,366	$ 371,163	$ 356,804	$ 322,540
Gross profit	15,450	24,404	33,502	29,726	31,202	26,199	15,675	15,737	103,082	88,813	66,173
Net income (loss)	$ (11,495)	$ (4,903)	$ 5,725	$ 6,307	$ 2,069	$ 2,272	$ (7,326)	$ (14,091)	$ (4,366)	$ (17,076)	$ (43,637)
Basic net income (loss) per share (USD per share)	$ (0.23)	$ (0.10)	$ 0.12	$ 0.13	$ 0.04	$ 0.05	$ (0.16)	$ (0.30)	$ (0.09)	$ (0.36)	$ (0.97)
Diluted net income (loss) per share (USD per share)	$ (0.23)	$ (0.10)	$ 0.11	$ 0.12	$ 0.04	$ 0.05	$ (0.16)	$ (0.30)	$ (0.09)	$ (0.36)	$ (0.97)
Weighted average shares used to compute basic net income (loss) per share (in shares)	50,256	49,936	49,077	48,615	48,358	47,666	46,754	46,414	49,474	47,304	45,144
Weighted average shares used to compute diluted net income (loss) per share (in shares)	50,256	49,936	51,661	50,617	50,238	48,615	46,754	46,414	49,474	47,304	45,144