Calix (CALX) 10-Q 10 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 04, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	CALIX, INC
Entity Central Index Key	1,406,666
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		51,971,783

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 42,628	$ 39,775
Accounts receivable, net	55,746	80,392
Inventory	27,061	31,529
Prepaid expenses and other current assets	12,551	10,759
Total current assets	137,986	162,455
Property and equipment, net	14,808	15,681
Goodwill	116,175	116,175
Other assets	1,943	759
Total assets	270,912	295,070
Current liabilities:
Accounts payable	17,836	35,977
Accrued liabilities	48,783	49,279
Deferred revenue	14,676	13,076
Line of credit	30,000	30,000
Total current liabilities	111,295	128,332
Long-term portion of deferred revenue	20,712	20,645
Other long-term liabilities	866	1,130
Total liabilities	132,873	150,107
Commitments and contingencies (See Note 7)
Stockholders’ equity:
Preferred stock, $0.025 par value; 5,000 shares authorized; no shares issued and outstanding as of March 31, 2018 and December 31, 2017	0	0
Common stock, $0.025 par value; 100,000 shares authorized; 57,047 shares issued and 51,717 shares outstanding as of March 31, 2018, and 56,839 shares issued and 51,509 shares outstanding as of December 31, 2017	1,426	1,421
Additional paid-in capital	853,809	851,054
Accumulated other comprehensive income (loss)	110	(169)
Accumulated deficit	(677,320)	(667,357)
Treasury stock, 5,330 shares as of March 31, 2018 and December 31, 2017	(39,986)	(39,986)
Total stockholders’ equity	138,039	144,963
Total liabilities and stockholders’ equity	$ 270,912	$ 295,070

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.025	$ 0.025
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.025	$ 0.025
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	57,047,000	56,839,000
Common stock, shares outstanding	51,717,000	51,509,000
Treasury stock, shares	5,330,000	5,330,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Apr. 01, 2017
Revenue:
Systems		$ 93,291	$ 91,605
Services		6,112	25,913
Total revenue		99,403	117,518
Cost of revenue:
Systems	[1]	51,633	57,373
Services	[1]	5,711	25,768
Total cost of revenue		57,344	83,141
Gross profit		42,059	34,377
Operating expenses:
Research and development	[1]	25,536	33,808
Sales and marketing	[1]	19,901	22,429
General and administrative	[1]	9,095	10,257
Gain on sale of product line		(6,704)	0
Restructuring charges		5,340	699
Total operating expenses		53,168	67,193
Loss from operations		(11,109)	(32,816)
Interest and other income (expense), net:
Interest income (expense), net		(223)	44
Other income (expense), net		(294)	120
Total interest and other income (expense), net		(517)	164
Loss before provision for income taxes		(11,626)	(32,652)
Provision for income taxes		110	673
Net loss		$ (11,736)	$ (33,325)
Net loss per common share:
Basic and diluted (in dollars per share)		$ (0.23)	$ (0.67)
Weighted-average number of shares used to compute net loss per common share:
Basic and diluted (in shares)		51,611	49,525
Other comprehensive loss, net of tax:
Unrealized gains (losses) on available-for-sale marketable securities, net		$ 0	$ (4)
Foreign currency translation adjustments, net		279	61
Total other comprehensive income, net of tax		279	57
Comprehensive loss		$ (11,457)	$ (33,268)
[1]	Includes stock-based compensation as follows: Three and Nine Months Ended March 31, 2018 and April 1, 2017; Cost of revenue: Products - $112, $116, $349, $338 ; Services - $77, $56, $200, $146; Research and development - $983, $1,326, $3,663, $3,719; Sales and marketing - $850, $1,111, $2,581, $3,323; General administrative - $735, $931, $2,521, $2,840;

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Systems
Stock-based compensation	$ 112	$ 116
Services
Stock-based compensation	77	56
Research and development
Stock-based compensation	983	1,326
Sales and marketing
Stock-based compensation	850	1,111
General and administrative
Stock-based compensation	$ 735	$ 931

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Operating activities:
Net loss	$ (11,736)	$ (33,325)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,757	3,540
Depreciation and amortization	2,623	2,463
Amortization of intangible assets	0	813
Loss on retirement of property and equipment	244	80
Gain on sale of product line	(6,704)	0
Amortization of discount related to available-for-sale securities	0	(5)
Changes in operating assets and liabilities:
Accounts receivable, net	25,137	(12,852)
Inventory	2,451	(1,993)
Prepaid expenses and other assets	(2,521)	(6,659)
Accounts payable	(17,871)	276
Accrued liabilities	(805)	7,110
Deferred revenue	866	17,201
Other long-term liabilities	(264)	(103)
Net cash used in operating activities	(5,823)	(23,454)
Investing activities:
Purchases of property and equipment	(1,875)	(2,106)
Purchases of marketable securities	0	(8,732)
Maturities of marketable securities	0	11,266
Proceeds from sale of product line	10,350	0
Net cash provided by investing activities	8,475	428
Financing activities:
Proceeds from exercise of stock options	8	13
Taxes paid for awards vested under equity incentive plan	(5)	(1,093)
Proceeds from line of credit	163,238	0
Repayment of line of credit	(163,238)	0
Net cash provided by (used in) financing activities	3	(1,080)
Effect of exchange rate changes on cash and cash equivalents	198	65
Net increase (decrease) in cash and cash equivalents	2,853	(24,041)
Cash and cash equivalents at beginning of period	39,775	50,359
Cash and cash equivalents at end of period	$ 42,628	$ 26,318

Company and Basis of Presentati

Company and Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company and Basis of Presentation	Company and Basis of Presentation Company Calix, Inc. (together with its subsidiaries, “Calix” or the “Company”) was incorporated in August 1999, and is a Delaware corporation. The Company is a leading global provider of cloud and software platforms, systems and services required to deliver the unified access network, smart home and business services of tomorrow. The Company’s platforms and services help its customers to build next generation networks by embracing a DevOps operating model, optimizing the subscriber experience by leveraging big data analytics and turn the complexity of the smart home and business into new revenue streams. The Company's cloud and software platforms, systems and services enable communication service providers (“CSPs”) to provide a wide range of revenue-generating services, from basic voice and data to advanced broadband services, over legacy and next-generation access networks. The Company focuses on CSP access networks, the portion of the network that governs available bandwidth and determines the range and quality of services that can be offered to subscribers. Basis of Presentation The accompanying unaudited condensed consolidated financial statements, including the accounts of Calix, Inc. and its wholly-owned subsidiaries, have been prepared in accordance with the requirements of the U.S. Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. generally accepted accounting principles (“GAAP”) can be condensed or omitted. In the opinion of management, the financial statements include all normal and recurring adjustments that are considered necessary for the fair presentation of the Company’s financial position and operating results. All significant intercompany balances and transactions have been eliminated in consolidation. The Condensed Consolidated Balance Sheet at December 31, 2017 has been derived from the audited financial statements at that date. The results of the Company’s operations can vary during each quarter of the year. Therefore, the results and trends in these interim financial statements may not be the same as those for the full year or any future periods. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the audited financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . The Company’s fiscal year begins on January 1st and ends on December 31st. Quarterly periods are based on a 4-4-5 calendar with the first, second and third quarters ending on the 13th Saturday of each fiscal period. As a result, the Company had one fewer day in the three months ended March 31, 2018 than in the three months ended April 1, 2017 . The preparation of financial statements in conformity with GAAP for interim financial reporting requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Liquidity and Capital Resources Since its inception, the Company has incurred significant losses, and as of March 31, 2018 , the Company had an accumulated deficit of $677.3 million . Based on its current operating plan and operating cash flows, management plans to finance its future operations and capital expenditures with existing cash and cash equivalents and its existing credit facility with Silicon Valley Bank (“SVB”), which it believes will be sufficient to fund its operations and capital expenditures through at least the next twelve months. See Note 5 for more information on the Company's credit facility with SVB. The Company may also need to seek other sources of liquidity, including the sale of equity or incremental borrowings, to support its working capital needs. However, there can be no assurances that such capital will be available on terms which are acceptable to the Company or at all or that the Company will achieve profitable operations. If the Company is unable to generate sufficient cash flows or obtain other sources of liquidity, the Company will be forced to limit its development activities, reduce its investment in growth initiatives and institute cost-cutting measures, all of which may adversely impact the Company’s business and growth. The accompanying consolidated financial statements do not include any adjustments that might result from the outcome of this uncertainty.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies The Company’s significant accounting policies are disclosed in its Annual Report on Form 10-K for the year ended December 31, 2017 . The Company’s significant accounting policies did not change during the three months ended March 31, 2018 , except for those impacted by the newly adopted accounting standard below. Newly Adopted Accounting Standards Revenue from Contracts with Customers In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which provides guidance for revenue recognition. ASU 2014-09 supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific guidance. Additionally, it supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition-Construction-Type and Production-Type Contracts, and creates new Subtopic 340-40, Other Assets and Deferred Costs-Contracts with Customers. The Company determines revenue recognition through the following steps: identification of the contract, or contracts, with a customer; identification of the performance obligations in the contract; determination of the transaction price; allocation of the transaction price to the performance obligations in the contract; and recognition of revenue when, or as, the Company satisfies a performance obligation. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the previous guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. The new standard permits adoption either by using (i) a full retrospective approach for all periods presented in the period of adoption or (ii) a modified retrospective approach with the cumulative effect of initially applying the new standard recognized at the date of initial application and providing certain additional disclosures. On January 1, 2018, the Company adopted Topic 606 and Subtopic 340-40 using the modified retrospective transition method applied to those contracts which were not completed as of January 1, 2018. Accordingly, results for reporting period beginning after January 1, 2018 are presented under Topic 606, while the comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company recognized the cumulative effect of initially applying the standards as an adjustment to the opening balance of accumulated deficit of $1.8 million as of January 1, 2018, with the impact primarily relating to deferring the costs of obtaining contracts (sales commissions) and the upfront recognition of software license revenue. The impact to revenue for the three months ended March 31, 2018 was an increase of $1.2 million as a result of applying Topic 606. Significant changes to the Company’s accounting policies as a result of adopting Topic 606 are discussed below. Revenue Recognition Revenue is recognized when a performance obligation is satisfied, which occurs when control of the promised goods or services is transferred to the customer, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in Topic 606. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. The Company’s hardware products contain both software and non-software components that function together to deliver the products’ essential functionality and therefore constitutes a single performance obligation as the promise to transfer the individual software and non-software components is not separately identifiable and, therefore, not distinct. The Company’s contracts may include multiple performance obligations. For such arrangements, the Company allocates the contract’s transaction price to each performance obligation using the relative stand-alone selling price of each distinct good or service in the contract. The Company generally determines stand-alone selling prices based on the prices charged to customers or its best estimate of stand-alone selling price. The Company’s estimate of stand-alone selling price is established considering multiple factors including, but not limited to, geographies, market conditions, competitive landscape, internal costs, gross margin objectives, characteristics of targeted customers and pricing practices. The determination of estimated stand-alone selling price is made through consultation with and formal approval by management, taking into consideration the go-to-market strategy. For certain revenue arrangements involving delivery of both systems and professional services, each is considered a distinct performance obligation. Systems revenue is recognized at a point in time when management has determined that control over systems has transferred to the customer, which is generally when legal title has transferred to the customer. For the same revenue arrangements, management believes that control of the associated professional services is transferred to the customer over time. As such, professional services revenue is recognized over the period in which the services are provided using a cost input measure. Prior to adoption of Topic 606, the Company recognized revenue (and corresponding cost of revenue) for systems and associated professional services under the same revenue arrangement as services were delivered and milestones were accepted by the customer and as the systems were installed or delivered to the customer. Accordingly, the Company now recognizes revenue when control of the systems and services has been transferred to the customer, which may be earlier than system installation or customer acceptance, in accordance with the agreed-upon specifications in the contract. The Company derives revenue from contracts with customers primarily from the following and categorizes its revenue as follows: • Systems include revenue derived from the sale of access systems and software and cloud-based platforms. • Services include revenue from professional services, software maintenance, support services for access systems, extended warranty and training services. The following is a summary of revenue disaggregated by geographic region based upon the location of the customers (in thousands): Three Months Ended March 31, 2018 April 1, 2017 United States $ 89,389 $ 106,528 Caribbean 1,137 947 Canada 2,286 1,512 Europe 1,227 1,577 Other 5,364 6,954 Total $ 99,403 $ 117,518 Concentration of Customer Risk The Company had one customer that accounted for more than 10% of its total revenue for the three months ended March 31, 2018 and two customers that each accounted for more than 10% of its total revenue for the three months ended April 1, 2017 . The one customer represented 14% of the Company’s total revenue for the three months ended March 31, 2018 . The two customers represented 55% of the Company’s total revenue for the three months ended April 1, 2017 . The one customer represented more than 10% of the Company’s accounts receivable as of March 31, 2018 and December 31, 2017 . Deferred Revenue Deferred revenue results from transactions where the Company billed the customer for products or services and when cash payments are received or due prior to transferring control of the promised goods or services to the customer. The increase in the deferred revenue balance for the three months ended March 31, 2018 is primarily driven by cash payments received or due in advance of satisfying our performance obligations, offset by $5.5 million of revenue recognized that was included in the deferred revenue balance at the beginning of the period. Revenue allocated to remaining performance obligations represent contract revenue that has not yet been recognized, which includes deferred revenue and amounts that will be invoiced and recognized as revenue in future periods. This amount was approximately $35.4 million as of the end of the first quarter of 2018 and the Company expects to recognize approximately 41.5% of such revenue over the next 12 months and the remainder thereafter. Payment terms to customers typically range from net 30 to net 90 days and vary by the type and location of customer and the products or services offered. The period between the transfer of control of the promised good or service to a customer and when payment is due is not significant. Contract Costs In connection with the adoption of Topic 606 on January 1, 2018, the Company also adopted the guidance in ASC 340-40, Other Assets and Deferred Costs - Contracts with Customers, with respect to capitalization and amortization of incremental costs of obtaining a contract. The new cost guidance requires the capitalization of all incremental costs incurred to obtain a contract with a customer that it would not have incurred if the contract had not been obtained, provided it expects to recover the costs. As a result of this new guidance, the Company capitalizes certain sales commissions related primarily to extended warranty and Calix Cloud products for which the expected amortization period is greater than one year. The Company expects that sales commissions as a result of obtaining customer contracts are recoverable, and therefore the Company defers and capitalizes them as contract costs. Capitalized commissions are amortized as sales and marketing expenses over the period that the related revenue is recognized, which typically range from three to ten years for extended warranty and cloud offerings. The Company classifies the unamortized portion of deferred commissions as current or noncurrent based on the timing of when the Company expects to recognize the expense. The current and noncurrent portions of deferred commissions are included in prepaid expenses and other current assets and other assets, respectively, in the Company’s Condensed Consolidated Balance Sheets. As of March 31, 2018, the unamortized balance of deferred commissions was $0.8 million . For the three months ended March 31, 2018, the amount of amortization was less than $0.1 million , and there was no impairment loss in relation to the costs capitalized. Practical Expedients The Company expenses sales commissions as sales and marketing expenses when incurred if the expected amortization period is one year or less. This applies generally to all transactions other than extended warranty contracts and Calix Cloud products. The Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which the Company recognizes revenue at the amount to which it has the right to invoice for services performed. The Company does not adjust the promised amount of consideration for the effects of a significant financing component if the Company expects, at contract inception, that the period between when the Company transfers a promised good or service to a customer and when the customer pays for that good or service will be one year or less. Cumulative Effect of Adoption The cumulative effect of changes made to the Condensed Consolidated January 1, 2018 Balance Sheet was as follows (in thousands): Balance at December 31, 2017 Adjustments Balance at January 1, 2018 Accounts receivable, net $ 80,392 $ 491 $ 80,883 Prepaid expenses and other current assets 10,759 (245 ) 10,514 Other assets 759 698 1,457 Total assets 295,070 944 296,014 Deferred revenue 13,076 (829 ) 12,247 Total liabilities 150,107 (829 ) 149,278 Accumulated deficit (667,357 ) 1,773 (665,584 ) Total liabilities and stockholders’ equity 295,070 944 296,014 The impact of adopting the new revenue standard on the Company’s consolidated financial statements as of and for the three months ended March 31, 2018 were as follows (in thousands): Condensed Consolidated Balance Sheet As of March 31, 2018 (Unaudited) As Reported Adjustments Balances Without Adoption of Topic 606 Accounts receivable, net $ 55,746 $ (2,071 ) $ 53,675 Prepaid expenses and other current assets 12,551 1,023 13,574 Other assets 1,943 (699 ) 1,244 Total assets 270,912 (1,747 ) 269,165 Accrued liabilities 48,783 (959 ) 47,824 Deferred revenue 14,676 1,427 16,103 Total liabilities 132,873 468 133,341 Accumulated deficit (677,320 ) (2,215 ) (679,535 ) Total liabilities and stockholders’ equity 270,912 (1,747 ) 269,165 Condensed Consolidated Statement of Comprehensive Loss Three Months Ended March 31, 2018 (Unaudited) As Reported Adjustments Balances Without Adoption of Topic 606 Revenue: Systems $ 93,291 $ (681 ) $ 92,610 Services 6,112 (539 ) 5,573 Total revenue 99,403 (1,220 ) 98,183 Cost of revenue: Systems 51,633 (485 ) 51,148 Services 5,711 (278 ) 5,433 Total cost of revenue 57,344 (763 ) 56,581 Gross profit 42,059 (457 ) 41,602 Sales and marketing 19,901 (15 ) 19,886 Net loss (11,736 ) (442 ) (12,178 ) Recent Accounting Pronouncements Not Yet Adopted Leases In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires recognition of an asset and liability for lease arrangements longer than twelve months. ASU 2016-02 will be effective for the Company beginning in the first quarter of 2019. Early application is permitted, and it is required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The Company is not planning to early adopt, and accordingly, it will adopt the new standard effective January 1, 2019. The Company intends to elect the available practical expedients on adoption. The Company is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. The Company expects its assets and liabilities to increase as the new standard requires recognition of right-of-use assets and lease liabilities for operating leases, but does not expect any material impact on its loss from operations or net loss as a result of the adoption of this standard. Income taxes On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 ("SAB 118") which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740, Income Taxes, for the year ended December 31, 2017. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Act for which the accounting under ASC 740 is complete. The Company has not completed their accounting for tax reform with respect to the December 31, 2017 year relating to the calculation of the transition tax. The Company is still within the measurement period as of the first quarter of 2018 and no further conclusions have been made, as the Company reviews SAB 118 and the impact to the Company.

Cash and Cash Equivalents

Cash and Cash Equivalents	3 Months Ended
	Mar. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consisted of the following (in thousands): March 31, December 31, Cash and cash equivalents: Cash $ 38,840 $ 35,999 Money market funds 3,788 3,776 $ 42,628 $ 39,775 The carrying amounts of the Company’s money market funds approximate their fair values due to their nature, duration and short maturities.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures its cash equivalents and marketable securities at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The Company utilizes the following three-tier value hierarchy which prioritizes the inputs used in measuring fair value: Level 1 – Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 – Observable inputs other than quoted prices included in Level 1 for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-driven valuations in which all significant inputs and significant value drivers are observable in active markets. Level 3 – Unobservable inputs to the valuation derived from fair valuation techniques in which one or more significant inputs or significant value drivers are unobservable. The following table sets forth the Company’s financial assets measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 , based on the three-tier fair value hierarchy (in thousands): As of March 31, 2018 Level 1 Level 2 Total Money market funds $ 3,788 $ — $ 3,788 3,788 $ — $ 3,788 As of December 31, 2017 Level 1 Level 2 Total Money market funds $ 3,776 $ — $ 3,776 $ 3,776 $ — $ 3,776 The fair values of money market funds classified as Level 1 were derived from quoted market prices as active markets for these instruments exist. The Company has no level 2 or level 3 financial assets.

Balance Sheet Details

Balance Sheet Details	3 Months Ended
	Mar. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	Balance Sheet Details Accounts receivable, net consisted of the following (in thousands): March 31, December 31, Accounts receivable $ 56,134 $ 81,793 Allowance for doubtful accounts (388 ) (579 ) Product return reserve (1) — (822 ) $ 55,746 $ 80,392 (1) With adoption of Topic 606 on January 1, 2018, the product return reserve is considered a contract liability and has been reclassified to accrued liabilities. Inventory consisted of the following (in thousands): March 31, December 31, Raw materials $ 2,244 $ 1,211 Finished goods 24,817 30,318 $ 27,061 $ 31,529 Property and equipment, net consisted of the following (in thousands): March 31, December 31, Test equipment $ 40,908 $ 39,952 Computer equipment and software 33,206 32,175 Furniture and fixtures 2,744 2,714 Leasehold improvements 5,206 6,029 Total 82,064 80,870 Accumulated depreciation and amortization (67,256 ) (65,189 ) $ 14,808 $ 15,681 Accrued liabilities consisted of the following (in thousands): March 31, December 31, Accrued compensation and related benefits $ 18,367 $ 15,563 Accrued warranty and retrofit 8,097 8,708 Accrued professional and consulting fees 5,349 9,604 Accrued restructuring charges 4,927 1,417 Accrued excess and obsolete inventory at contract manufacturers 3,371 2,430 Accrued non-income related taxes 1,604 1,778 Customer over payments 968 1,050 Product return reserve 959 — Accrued insurance 717 827 Accrued freight 695 593 Accrued business events — 1,272 Accrued other 3,729 6,037 $ 48,783 $ 49,279 Accrued Warranty and Retrofit The Company provides a standard warranty for its hardware products. Hardware generally has a one -, three - or five -year standard warranty from the date of shipment. Under certain circumstances, the Company also provides fixes on specifically identified performance failures for products that are outside of the standard warranty period and recognizes estimated costs related to retrofit activities upon identification of such product failures. The Company accrues for potential warranty and retrofit claims based on the Company’s historical product failure rates and historical costs incurred in correcting product failures along with other relevant information related to any specifically identified product failures. The Company’s warranty and retrofit accruals are based on estimates of losses that are probable based on information available. The adequacy of the accrual is reviewed on a periodic basis and adjusted, if necessary, based on additional information as it becomes available. Changes in the Company’s warranty and retrofit reserves in the periods as indicated were as follows (in thousands): Three Months Ended March 31, April 1, Balance at beginning of period $ 8,708 $ 12,214 Provision for warranty and retrofit charged to cost of revenue 1,469 1,862 Utilization of reserve (2,080 ) (3,298 ) Balance at end of period $ 8,097 $ 10,778 Accrued Restructuring Charges The Company adopted a restructuring plan in March 2017. This restructuring plan realigned the Company’s business, increasing its focus towards its investments in software defined access and cloud products, while reducing its expense structure in its traditional systems business. The Company began to take actions under this plan beginning in March 2017 and recognized $4.2 million of restructuring charges for the year ended December 31, 2017 consisting primarily of severance and other one-time termination benefits. Actions pursuant to this restructuring plan were complete as of December 31, 2017. The Company established a new restructuring plan in February 2018 to further realign its business resources based on the production releases of its platform offerings. The Company incurred restructuring charges of approximately $5.3 million , consisting of primarily of severance and other termination related benefits, in the first quarter of 2018. The following table summarizes the activities pursuant to the above restructuring plans (in thousands): Severance and Related Benefits Facilities Balance at December 31, 2017 $ 975 $ 442 Restructuring charges 4,567 773 Cash payments (1,501 ) (329 ) Balance at March 31, 2018 $ 4,041 $ 886 Deferred revenue consisted of the following (in thousands): March 31, December 31, Current: Products and services $ 10,675 $ 9,125 Extended warranty 4,001 3,951 14,676 13,076 Long-term: Products and services 493 18 Extended warranty 20,219 20,627 20,712 20,645 $ 35,388 $ 33,721

Credit Facility

Credit Facility	3 Months Ended
	Mar. 31, 2018
Line of Credit Facility [Abstract]
Credit Facility	Credit Facility On August 7, 2017, the Company entered into a loan and security agreement (the “Loan Agreement”) with SVB. The Loan Agreement provides for a senior secured revolving credit facility with SVB, pursuant to which SVB agreed to make revolving advances available to the Company in a principal amount of up to $30.0 million based on a customary accounts receivable borrowing base, subject to certain exceptions for accounts originating outside the United States and certain specific accounts, which could reduce the amount available to the Company under the credit facility. The credit facility matures, and all outstanding amounts become due and payable, on August 7, 2019. The credit facility includes affirmative and negative covenants applicable to the Company and its subsidiaries. Furthermore, the Loan Agreement requires the Company to maintain a liquidity ratio at minimum levels set forth in more detail in the Loan Agreement. The credit facility also includes events of default, the occurrence and continuation of which would provide SVB with the right to demand immediate repayment of any principal and unpaid interest under the credit facility, and to exercise remedies against the Company and the collateral securing the loans under the credit facility. For the month ended November 30, 2017, the Company was not able to maintain the minimum Adjusted Quick Ratio (as defined in the Loan Agreement) at the level required in the Loan Agreement, which constituted an event of default. Although SVB waived this event of default effective as of November 30, 2017 and, therefore, this default did not change the Company’s ability to borrow under the Loan Agreement, the Company was required to amend certain covenants under the Loan Agreement. In February 2018, the Company entered into an amendment to the Loan Agreement that, among other things, amended certain affirmative financial covenants, including reductions to the required minimum level of the Adjusted Quick Ratio and the inclusion of an additional financial covenant related to the maintenance of Adjusted EBITDA (as defined in the Loan Agreement). As of March 31, 2018 , the Company was in compliance with these requirements. As of March 31, 2018 , the Company had borrowings outstanding of $30.0 million , representing the full amount available under the line of credit.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Lease Commitments The Company leases office space under non-cancelable operating leases. Certain of the Company’s operating leases contain renewal options and rent acceleration clauses. Future minimum payments under the non-cancelable operating leases consisted of the following as of March 31, 2018 (in thousands): Period Minimum Future Lease Payments Remainder of 2018 $ 2,403 2019 3,227 2020 2,947 2021 2,531 2022 2,332 Thereafter 6,927 $ 20,367 The Company leases its headquarters office space in Petaluma, California under a lease agreement (“Petaluma Lease”) that expires February 2019. The above table also includes future minimum lease payments for our facilities in Minneapolis, Minnesota; Nanjing, China; Richardson, Texas; and San Jose and Santa Barbara, California, which expire at various dates through 2025. In March 2018, the Company entered into a new office lease agreement for 65,000 square feet in San Jose, California as its current office lease in San Jose, California expires in August 2018. The lease commences in August 2018 for a term of 87 months . The future minimum lease payments under the lease are approximately $16.1 million and are included in the table above. For the three months ended March 31, 2018 , total rent expense of the Company was $0.8 million . For the three months ended April 1, 2017 , total rent expense of the Company was $0.9 million . Purchase Commitments The Company’s primary contract manufacturers place orders for component inventory in advance based upon the Company’s build forecasts in order to reduce manufacturing lead times and ensure adequate component supply. The components are used by the contract manufacturers to build the products included in the build forecasts. The Company generally does not take ownership of the components held by contract manufacturers. The Company places purchase orders with its contract manufacturers in order to fulfill its monthly finished product inventory requirements. The Company incurs a liability when the contract manufacturer has converted the component inventory to a finished product and takes ownership of the inventory when transferred to the designated shipping warehouse. In the event of termination of services with a contract manufacturer, the Company may be required to purchase the remaining components inventory held by the contract manufacturer as well as any outstanding orders pursuant to the contractual provisions with such contract manufacturer. As of March 31, 2018 , the Company had approximately $57.4 million of outstanding purchase commitments for inventories to be delivered by its suppliers, including contract manufacturers, within one year. The Company has from time to time, and subject to certain conditions, reimbursed its primary contract manufacturer for component inventory purchases when this inventory has been rendered excess or obsolete, for example due to manufacturing and engineering change orders resulting from design changes, manufacturing discontinuation of parts by its suppliers, or in cases where inventory levels greatly exceed projected demand. The estimated excess and obsolete inventory liabilities related to such manufacturing and engineering change orders and other factors, which are included in accrued liabilities in the accompanying balance sheets, were $3.4 million and $2.4 million as of March 31, 2018 and December 31, 2017 , respectively. The Company records the related charges in cost of systems revenue in its Condensed Consolidated Statements of Comprehensive Loss. In March 2018, the Company entered into an agreement with a vendor for engineering services pursuant to which the Company will be obligated to make future minimum payments of $17.5 million through 2022. Litigation From time to time, the Company is involved in various legal proceedings arising from the normal course of business activities. The Company is not currently a party to any legal proceedings that, if determined adversely to the Company, in management’s opinion, are currently expected to individually or in the aggregate have a material adverse effect on the Company’s business, operating results or financial condition taken as a whole.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Equity Incentive Plans As of March 31, 2018 , the Company maintains two equity incentive plans, the 2002 Stock Plan and the 2010 Equity Incentive Award Plan (together, the “Plans”). These plans were approved by the stockholders and are described in the Company’s Annual Report on Form 10-K filed with the SEC on March 14, 2018 . Currently, the Company only grants shares from the 2010 Equity Incentive Award Plan. To date, awards granted under the Plans consist of stock options, restricted stock units (“RSUs”) and performance restricted stock units (“PRSUs”). Stock Options During the three months ended March 31, 2018 , 65,000 shares of stock options were granted with a grant date fair value of $6.20 per share. In August 2017, the Company granted 1.2 million shares of performance-based stock option awards to its executives. In February 2018, the Compensation Committee of the Company’s Board of Directors concluded that the performance target was not met and all such performance-based stock options were forfeited and canceled at that time. During the three months ended March 31, 2018 , 1,420 shares of stock options were exercised at a weighted-average exercise price of $5.42 per share. As of March 31, 2018 , unrecognized stock-based compensation expense of $3.7 million related to stock options, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 2.9 years . Restricted Stock Units During the three months ended March 31, 2018 , 27,586 shares of RSUs were granted with a grant date fair value of $7.25 per share. During the three months ended March 31, 2018 , 152,821 shares of RSUs vested. As of March 31, 2018 , unrecognized stock-based compensation expense of $6.6 million related to RSUs, net of estimated forfeitures, was expected to be recognized over a weighted-average period of 1.6 years . Performance Restricted Stock Units During the three months ended March 31, 2018 , 75,000 PRSUs vested. As of March 31, 2018 , unrecognized stock-based compensation expense of $0.1 million related to PRSUs, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 0.9 years . Employee Stock Purchase Plans The Company’s Amended and Restated Employee Stock Purchase Plan (“ESPP”) allows employees to purchase shares of the Company’s common stock through payroll deductions of up to 15% of their annual compensation subject to certain Internal Revenue Code limitations. In addition, no participant may purchase more than 2,000 shares of common stock in each offering period. The offering periods under the ESPP are six-month periods commencing on May 15 th and November 15 th of each year. The price of common stock purchased under the ESPP is 85% of the lower of the fair market value of the common stock on the commencement date and the end date of each six -month offering period. As of March 31, 2018 , there were 2.5 million shares available for issuance under the ESPP. During the three months ended March 31, 2018 , no shares were purchased under the ESPP. As of March 31, 2018 , unrecognized stock-based compensation expense of $0.2 million related to the ESPP is expected to be recognized over a remaining service period of 1.5 months. Under the 2017 Nonqualified Employee Stock Purchase Plan (“Nonqualified ESPP”), eligible employees can purchase shares of the Company’s common stock through payroll deductions of up to 25% of their annual compensation. Eligible employees have the right to (a) purchase the maximum number of whole shares of common stock that can be purchased with the elected payroll deductions during each offering period for which the employee is enrolled at a purchase price equal to the closing price of the Company’s common stock on the last day of such offering period and (b) receive an equal number of shares of the Company’s common stock that are subject to a risk of forfeiture in the event the employee terminates employment within the one year period immediately following the purchase date. The Nonqualified ESPP provides two six -month offering periods, from January 1 through June 30 and July 1 through December 31 of each year. The maximum number of shares of common stock currently authorized for issuance under the Nonqualified ESPP is 1,000,000 shares, with a maximum of 500,000 shares allocated per purchase period. As of March 31, 2018 , there were 0.6 million shares available for issuance under the Nonqualified ESPP. As of March 31, 2018 , unrecognized stock-based compensation expense of $1.8 million related to the Nonqualified ESPP is expected to be recognized over a remaining service period of 0.9 years .

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Income (Loss) The table below summarizes the changes in accumulated other comprehensive income (loss) by component for the periods indicated (in thousands): Three Months Ended March 31, 2018 April 1, 2017 Foreign Currency Translation Adjustments Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ (169 ) $ (6 ) $ (650 ) $ (656 ) Other comprehensive income (loss) 279 (4 ) 61 57 Balance at end of period $ 110 $ (10 ) $ (589 ) $ (599 ) Realized gains and losses on sales of available-for-sale marketable securities, if any, are reclassified from accumulated other comprehensive loss to “Other income (expense)” in the accompanying Condensed Consolidated Statements of Comprehensive Loss.

Product Line Divestiture

Product Line Divestiture	3 Months Ended
	Mar. 31, 2018
Discontinued Operations and Disposal Groups [Abstract]
Product Line Divestiture	Product Line Divestiture In February 2018, the Company sold its outdoor cabinet product line to Clearfield, Inc. (“Clearfield”) for $10.4 million in cash as well as the assumption by Clearfield of the related product warranty liabilities and open purchase order commitments with its contract manufacturer. The Company transferred $2.1 million in net inventory and agreed to solicit orders on Clearfield’s behalf on the newly transferred outdoor cabinets product lines free of charge for 15 months . The Company established a liability of $1.6 million in deferred revenue for providing this service and is amortizing this amount to service revenue over the corresponding 15-month period. The Company also recognized a $6.7 million gain for the three months ended March 31, 2018 within operating expenses in the Condensed Consolidated Statements of Comprehensive Loss.

Net Income (Loss) Per Common Sh

Net Income (Loss) Per Common Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Net Income (Loss) Per Common Share	Net Loss Per Common Share The following table sets forth the computation of basic and diluted net loss per common share for the periods indicated (in thousands, except per share data): Three Months Ended March 31, April 1, Numerator: Net loss $ (11,736 ) $ (33,325 ) Denominator: Weighted-average common shares outstanding used to compute basic net loss per share 51,611 49,525 Basic and diluted net loss per common share $ (0.23 ) $ (0.67 ) Potentially dilutive shares, weighted average 6,870 6,145 Potentially dilutive shares have been excluded from the computation of diluted net loss per common share when their effect is antidilutive. These antidilutive shares were primarily from stock options, restricted stock units and performance restricted stock units. For each of the periods presented where the Company reported a net loss, the effect of all potentially dilutive securities would be antidilutive, and as a result diluted net loss per common share is the same as basic net loss per common share.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table presents the provision for income taxes from continuing operations and the effective tax rates for the periods indicated (in thousands, except percentages): Three Months Ended March 31, April 1, Provision for income taxes $ 110 $ 673 Effective tax rate (0.9 )% (2.1 )% The income tax provision for the three months ended March 31, 2018 and April 1, 2017 consisted primarily of foreign and state income taxes. The effective tax rate for the three months ended March 31, 2018 and April 1, 2017 was determined using an estimated annual effective tax rate adjusted for discrete items, if any, that occurred during the respective periods. The Company’s effective tax rate for the three months ended March 31, 2018 and April 1, 2017 is impacted by the change in foreign income tax expense. Deferred tax assets are recognized if realization of such assets is more likely than not. The Company has established and continues to maintain a full valuation allowance against its net deferred tax assets, with the exception of certain foreign deferred tax assets, as the Company does not believe that realization of those assets is more likely than not . The Company’s effective tax rate may be subject to fluctuation during the year as new information is obtained, which may affect the assumptions used to estimate the annual effective tax rate, including factors such as the mix of forecasted pre-tax earnings in the various jurisdictions in which it operates, valuation allowances against deferred tax assets, the recognition or de-recognition of tax benefits related to uncertain tax positions, and changes in or the interpretation of tax laws in jurisdictions where it conducts business .

Significant Accounting Polici19

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Newly Adopted Accounting Standards Revenue from Contracts with Customers In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which provides guidance for revenue recognition. ASU 2014-09 supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific guidance. Additionally, it supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition-Construction-Type and Production-Type Contracts, and creates new Subtopic 340-40, Other Assets and Deferred Costs-Contracts with Customers. The Company determines revenue recognition through the following steps: identification of the contract, or contracts, with a customer; identification of the performance obligations in the contract; determination of the transaction price; allocation of the transaction price to the performance obligations in the contract; and recognition of revenue when, or as, the Company satisfies a performance obligation. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the previous guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. The new standard permits adoption either by using (i) a full retrospective approach for all periods presented in the period of adoption or (ii) a modified retrospective approach with the cumulative effect of initially applying the new standard recognized at the date of initial application and providing certain additional disclosures. On January 1, 2018, the Company adopted Topic 606 and Subtopic 340-40 using the modified retrospective transition method applied to those contracts which were not completed as of January 1, 2018. Accordingly, results for reporting period beginning after January 1, 2018 are presented under Topic 606, while the comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company recognized the cumulative effect of initially applying the standards as an adjustment to the opening balance of accumulated deficit of $1.8 million as of January 1, 2018, with the impact primarily relating to deferring the costs of obtaining contracts (sales commissions) and the upfront recognition of software license revenue. The impact to revenue for the three months ended March 31, 2018 was an increase of $1.2 million as a result of applying Topic 606. Significant changes to the Company’s accounting policies as a result of adopting Topic 606 are discussed below. Revenue Recognition Revenue is recognized when a performance obligation is satisfied, which occurs when control of the promised goods or services is transferred to the customer, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in Topic 606. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. The Company’s hardware products contain both software and non-software components that function together to deliver the products’ essential functionality and therefore constitutes a single performance obligation as the promise to transfer the individual software and non-software components is not separately identifiable and, therefore, not distinct. The Company’s contracts may include multiple performance obligations. For such arrangements, the Company allocates the contract’s transaction price to each performance obligation using the relative stand-alone selling price of each distinct good or service in the contract. The Company generally determines stand-alone selling prices based on the prices charged to customers or its best estimate of stand-alone selling price. The Company’s estimate of stand-alone selling price is established considering multiple factors including, but not limited to, geographies, market conditions, competitive landscape, internal costs, gross margin objectives, characteristics of targeted customers and pricing practices. The determination of estimated stand-alone selling price is made through consultation with and formal approval by management, taking into consideration the go-to-market strategy. For certain revenue arrangements involving delivery of both systems and professional services, each is considered a distinct performance obligation. Systems revenue is recognized at a point in time when management has determined that control over systems has transferred to the customer, which is generally when legal title has transferred to the customer. For the same revenue arrangements, management believes that control of the associated professional services is transferred to the customer over time. As such, professional services revenue is recognized over the period in which the services are provided using a cost input measure. Prior to adoption of Topic 606, the Company recognized revenue (and corresponding cost of revenue) for systems and associated professional services under the same revenue arrangement as services were delivered and milestones were accepted by the customer and as the systems were installed or delivered to the customer. Accordingly, the Company now recognizes revenue when control of the systems and services has been transferred to the customer, which may be earlier than system installation or customer acceptance, in accordance with the agreed-upon specifications in the contract. The Company derives revenue from contracts with customers primarily from the following and categorizes its revenue as follows: • Systems include revenue derived from the sale of access systems and software and cloud-based platforms. • Services include revenue from professional services, software maintenance, support services for access systems, extended warranty and training services. The following is a summary of revenue disaggregated by geographic region based upon the location of the customers (in thousands): Three Months Ended March 31, 2018 April 1, 2017 United States $ 89,389 $ 106,528 Caribbean 1,137 947 Canada 2,286 1,512 Europe 1,227 1,577 Other 5,364 6,954 Total $ 99,403 $ 117,518 Concentration of Customer Risk The Company had one customer that accounted for more than 10% of its total revenue for the three months ended March 31, 2018 and two customers that each accounted for more than 10% of its total revenue for the three months ended April 1, 2017 . The one customer represented 14% of the Company’s total revenue for the three months ended March 31, 2018 . The two customers represented 55% of the Company’s total revenue for the three months ended April 1, 2017 . The one customer represented more than 10% of the Company’s accounts receivable as of March 31, 2018 and December 31, 2017 . Deferred Revenue Deferred revenue results from transactions where the Company billed the customer for products or services and when cash payments are received or due prior to transferring control of the promised goods or services to the customer. The increase in the deferred revenue balance for the three months ended March 31, 2018 is primarily driven by cash payments received or due in advance of satisfying our performance obligations, offset by $5.5 million of revenue recognized that was included in the deferred revenue balance at the beginning of the period. Revenue allocated to remaining performance obligations represent contract revenue that has not yet been recognized, which includes deferred revenue and amounts that will be invoiced and recognized as revenue in future periods. This amount was approximately $35.4 million as of the end of the first quarter of 2018 and the Company expects to recognize approximately 41.5% of such revenue over the next 12 months and the remainder thereafter. Payment terms to customers typically range from net 30 to net 90 days and vary by the type and location of customer and the products or services offered. The period between the transfer of control of the promised good or service to a customer and when payment is due is not significant. Contract Costs In connection with the adoption of Topic 606 on January 1, 2018, the Company also adopted the guidance in ASC 340-40, Other Assets and Deferred Costs - Contracts with Customers, with respect to capitalization and amortization of incremental costs of obtaining a contract. The new cost guidance requires the capitalization of all incremental costs incurred to obtain a contract with a customer that it would not have incurred if the contract had not been obtained, provided it expects to recover the costs. As a result of this new guidance, the Company capitalizes certain sales commissions related primarily to extended warranty and Calix Cloud products for which the expected amortization period is greater than one year. The Company expects that sales commissions as a result of obtaining customer contracts are recoverable, and therefore the Company defers and capitalizes them as contract costs. Capitalized commissions are amortized as sales and marketing expenses over the period that the related revenue is recognized, which typically range from three to ten years for extended warranty and cloud offerings. The Company classifies the unamortized portion of deferred commissions as current or noncurrent based on the timing of when the Company expects to recognize the expense. The current and noncurrent portions of deferred commissions are included in prepaid expenses and other current assets and other assets, respectively, in the Company’s Condensed Consolidated Balance Sheets. As of March 31, 2018, the unamortized balance of deferred commissions was $0.8 million . For the three months ended March 31, 2018, the amount of amortization was less than $0.1 million , and there was no impairment loss in relation to the costs capitalized. Practical Expedients The Company expenses sales commissions as sales and marketing expenses when incurred if the expected amortization period is one year or less. This applies generally to all transactions other than extended warranty contracts and Calix Cloud products. The Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which the Company recognizes revenue at the amount to which it has the right to invoice for services performed. The Company does not adjust the promised amount of consideration for the effects of a significant financing component if the Company expects, at contract inception, that the period between when the Company transfers a promised good or service to a customer and when the customer pays for that good or service will be one year or less. Cumulative Effect of Adoption The cumulative effect of changes made to the Condensed Consolidated January 1, 2018 Balance Sheet was as follows (in thousands): Balance at December 31, 2017 Adjustments Balance at January 1, 2018 Accounts receivable, net $ 80,392 $ 491 $ 80,883 Prepaid expenses and other current assets 10,759 (245 ) 10,514 Other assets 759 698 1,457 Total assets 295,070 944 296,014 Deferred revenue 13,076 (829 ) 12,247 Total liabilities 150,107 (829 ) 149,278 Accumulated deficit (667,357 ) 1,773 (665,584 ) Total liabilities and stockholders’ equity 295,070 944 296,014 The impact of adopting the new revenue standard on the Company’s consolidated financial statements as of and for the three months ended March 31, 2018 were as follows (in thousands): Condensed Consolidated Balance Sheet As of March 31, 2018 (Unaudited) As Reported Adjustments Balances Without Adoption of Topic 606 Accounts receivable, net $ 55,746 $ (2,071 ) $ 53,675 Prepaid expenses and other current assets 12,551 1,023 13,574 Other assets 1,943 (699 ) 1,244 Total assets 270,912 (1,747 ) 269,165 Accrued liabilities 48,783 (959 ) 47,824 Deferred revenue 14,676 1,427 16,103 Total liabilities 132,873 468 133,341 Accumulated deficit (677,320 ) (2,215 ) (679,535 ) Total liabilities and stockholders’ equity 270,912 (1,747 ) 269,165 Condensed Consolidated Statement of Comprehensive Loss Three Months Ended March 31, 2018 (Unaudited) As Reported Adjustments Balances Without Adoption of Topic 606 Revenue: Systems $ 93,291 $ (681 ) $ 92,610 Services 6,112 (539 ) 5,573 Total revenue 99,403 (1,220 ) 98,183 Cost of revenue: Systems 51,633 (485 ) 51,148 Services 5,711 (278 ) 5,433 Total cost of revenue 57,344 (763 ) 56,581 Gross profit 42,059 (457 ) 41,602 Sales and marketing 19,901 (15 ) 19,886 Net loss (11,736 ) (442 ) (12,178 ) Recent Accounting Pronouncements Not Yet Adopted Leases In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires recognition of an asset and liability for lease arrangements longer than twelve months. ASU 2016-02 will be effective for the Company beginning in the first quarter of 2019. Early application is permitted, and it is required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The Company is not planning to early adopt, and accordingly, it will adopt the new standard effective January 1, 2019. The Company intends to elect the available practical expedients on adoption. The Company is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. The Company expects its assets and liabilities to increase as the new standard requires recognition of right-of-use assets and lease liabilities for operating leases, but does not expect any material impact on its loss from operations or net loss as a result of the adoption of this standard. Income taxes On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 ("SAB 118") which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740, Income Taxes, for the year ended December 31, 2017. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Act for which the accounting under ASC 740 is complete. The Company has not completed their accounting for tax reform with respect to the December 31, 2017 year relating to the calculation of the transition tax. The Company is still within the measurement period as of the first quarter of 2018 and no further conclusions have been made, as the Company reviews SAB 118 and the impact to the Company.
Revenue Recognition	Revenue Recognition Revenue is recognized when a performance obligation is satisfied, which occurs when control of the promised goods or services is transferred to the customer, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in Topic 606. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. The Company’s hardware products contain both software and non-software components that function together to deliver the products’ essential functionality and therefore constitutes a single performance obligation as the promise to transfer the individual software and non-software components is not separately identifiable and, therefore, not distinct. The Company’s contracts may include multiple performance obligations. For such arrangements, the Company allocates the contract’s transaction price to each performance obligation using the relative stand-alone selling price of each distinct good or service in the contract. The Company generally determines stand-alone selling prices based on the prices charged to customers or its best estimate of stand-alone selling price. The Company’s estimate of stand-alone selling price is established considering multiple factors including, but not limited to, geographies, market conditions, competitive landscape, internal costs, gross margin objectives, characteristics of targeted customers and pricing practices. The determination of estimated stand-alone selling price is made through consultation with and formal approval by management, taking into consideration the go-to-market strategy. For certain revenue arrangements involving delivery of both systems and professional services, each is considered a distinct performance obligation. Systems revenue is recognized at a point in time when management has determined that control over systems has transferred to the customer, which is generally when legal title has transferred to the customer. For the same revenue arrangements, management believes that control of the associated professional services is transferred to the customer over time. As such, professional services revenue is recognized over the period in which the services are provided using a cost input measure. Prior to adoption of Topic 606, the Company recognized revenue (and corresponding cost of revenue) for systems and associated professional services under the same revenue arrangement as services were delivered and milestones were accepted by the customer and as the systems were installed or delivered to the customer. Accordingly, the Company now recognizes revenue when control of the systems and services has been transferred to the customer, which may be earlier than system installation or customer acceptance, in accordance with the agreed-upon specifications in the contract. The Company derives revenue from contracts with customers primarily from the following and categorizes its revenue as follows: • Systems include revenue derived from the sale of access systems and software and cloud-based platforms. • Services include revenue from professional services, software maintenance, support services for access systems, extended warranty and training services.

Significant Accounting Polici20

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Disaggregation of Revenue	The following is a summary of revenue disaggregated by geographic region based upon the location of the customers (in thousands): Three Months Ended March 31, 2018 April 1, 2017 United States $ 89,389 $ 106,528 Caribbean 1,137 947 Canada 2,286 1,512 Europe 1,227 1,577 Other 5,364 6,954 Total $ 99,403 $ 117,518
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The cumulative effect of changes made to the Condensed Consolidated January 1, 2018 Balance Sheet was as follows (in thousands): Balance at December 31, 2017 Adjustments Balance at January 1, 2018 Accounts receivable, net $ 80,392 $ 491 $ 80,883 Prepaid expenses and other current assets 10,759 (245 ) 10,514 Other assets 759 698 1,457 Total assets 295,070 944 296,014 Deferred revenue 13,076 (829 ) 12,247 Total liabilities 150,107 (829 ) 149,278 Accumulated deficit (667,357 ) 1,773 (665,584 ) Total liabilities and stockholders’ equity 295,070 944 296,014 The impact of adopting the new revenue standard on the Company’s consolidated financial statements as of and for the three months ended March 31, 2018 were as follows (in thousands): Condensed Consolidated Balance Sheet As of March 31, 2018 (Unaudited) As Reported Adjustments Balances Without Adoption of Topic 606 Accounts receivable, net $ 55,746 $ (2,071 ) $ 53,675 Prepaid expenses and other current assets 12,551 1,023 13,574 Other assets 1,943 (699 ) 1,244 Total assets 270,912 (1,747 ) 269,165 Accrued liabilities 48,783 (959 ) 47,824 Deferred revenue 14,676 1,427 16,103 Total liabilities 132,873 468 133,341 Accumulated deficit (677,320 ) (2,215 ) (679,535 ) Total liabilities and stockholders’ equity 270,912 (1,747 ) 269,165 Condensed Consolidated Statement of Comprehensive Loss Three Months Ended March 31, 2018 (Unaudited) As Reported Adjustments Balances Without Adoption of Topic 606 Revenue: Systems $ 93,291 $ (681 ) $ 92,610 Services 6,112 (539 ) 5,573 Total revenue 99,403 (1,220 ) 98,183 Cost of revenue: Systems 51,633 (485 ) 51,148 Services 5,711 (278 ) 5,433 Total cost of revenue 57,344 (763 ) 56,581 Gross profit 42,059 (457 ) 41,602 Sales and marketing 19,901 (15 ) 19,886 Net loss (11,736 ) (442 ) (12,178 )

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	3 Months Ended
	Mar. 31, 2018
Cash and Cash Equivalents [Abstract]
Summary of cash and cash equivalents	Cash and cash equivalents consisted of the following (in thousands): March 31, December 31, Cash and cash equivalents: Cash $ 38,840 $ 35,999 Money market funds 3,788 3,776 $ 42,628 $ 39,775

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Summary of fair values of financial assets	The following table sets forth the Company’s financial assets measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 , based on the three-tier fair value hierarchy (in thousands): As of March 31, 2018 Level 1 Level 2 Total Money market funds $ 3,788 $ — $ 3,788 3,788 $ — $ 3,788 As of December 31, 2017 Level 1 Level 2 Total Money market funds $ 3,776 $ — $ 3,776 $ 3,776 $ — $ 3,776

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	3 Months Ended
	Mar. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Summary of accounts receivable, net	Accounts receivable, net consisted of the following (in thousands): March 31, December 31, Accounts receivable $ 56,134 $ 81,793 Allowance for doubtful accounts (388 ) (579 ) Product return reserve (1) — (822 ) $ 55,746 $ 80,392 (1) With adoption of Topic 606 on January 1, 2018, the product return reserve is considered a contract liability and has been reclassified to accrued liabilities.
Summary of inventory	Inventory consisted of the following (in thousands): March 31, December 31, Raw materials $ 2,244 $ 1,211 Finished goods 24,817 30,318 $ 27,061 $ 31,529
Summary of property and equipment, net	Property and equipment, net consisted of the following (in thousands): March 31, December 31, Test equipment $ 40,908 $ 39,952 Computer equipment and software 33,206 32,175 Furniture and fixtures 2,744 2,714 Leasehold improvements 5,206 6,029 Total 82,064 80,870 Accumulated depreciation and amortization (67,256 ) (65,189 ) $ 14,808 $ 15,681
Summary of accrued liabilities	Accrued liabilities consisted of the following (in thousands): March 31, December 31, Accrued compensation and related benefits $ 18,367 $ 15,563 Accrued warranty and retrofit 8,097 8,708 Accrued professional and consulting fees 5,349 9,604 Accrued restructuring charges 4,927 1,417 Accrued excess and obsolete inventory at contract manufacturers 3,371 2,430 Accrued non-income related taxes 1,604 1,778 Customer over payments 968 1,050 Product return reserve 959 — Accrued insurance 717 827 Accrued freight 695 593 Accrued business events — 1,272 Accrued other 3,729 6,037 $ 48,783 $ 49,279
Product warranty activities	Changes in the Company’s warranty and retrofit reserves in the periods as indicated were as follows (in thousands): Three Months Ended March 31, April 1, Balance at beginning of period $ 8,708 $ 12,214 Provision for warranty and retrofit charged to cost of revenue 1,469 1,862 Utilization of reserve (2,080 ) (3,298 ) Balance at end of period $ 8,097 $ 10,778
Summary of restructuring activities	The following table summarizes the activities pursuant to the above restructuring plans (in thousands): Severance and Related Benefits Facilities Balance at December 31, 2017 $ 975 $ 442 Restructuring charges 4,567 773 Cash payments (1,501 ) (329 ) Balance at March 31, 2018 $ 4,041 $ 886
Summary of deferred revenue	Deferred revenue consisted of the following (in thousands): March 31, December 31, Current: Products and services $ 10,675 $ 9,125 Extended warranty 4,001 3,951 14,676 13,076 Long-term: Products and services 493 18 Extended warranty 20,219 20,627 20,712 20,645 $ 35,388 $ 33,721

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum rental payments for operating leases	Future minimum payments under the non-cancelable operating leases consisted of the following as of March 31, 2018 (in thousands): Period Minimum Future Lease Payments Remainder of 2018 $ 2,403 2019 3,227 2020 2,947 2021 2,531 2022 2,332 Thereafter 6,927 $ 20,367

Accumulated Other Comprehensi25

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Accumulated other comprehensive income details	The table below summarizes the changes in accumulated other comprehensive income (loss) by component for the periods indicated (in thousands): Three Months Ended March 31, 2018 April 1, 2017 Foreign Currency Translation Adjustments Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ (169 ) $ (6 ) $ (650 ) $ (656 ) Other comprehensive income (loss) 279 (4 ) 61 57 Balance at end of period $ 110 $ (10 ) $ (589 ) $ (599 )

Net Income (Loss) Per Common 26

Net Income (Loss) Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of net income (loss) per share	The following table sets forth the computation of basic and diluted net loss per common share for the periods indicated (in thousands, except per share data): Three Months Ended March 31, April 1, Numerator: Net loss $ (11,736 ) $ (33,325 ) Denominator: Weighted-average common shares outstanding used to compute basic net loss per share 51,611 49,525 Basic and diluted net loss per common share $ (0.23 ) $ (0.67 ) Potentially dilutive shares, weighted average 6,870 6,145

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of income taxes	The following table presents the provision for income taxes from continuing operations and the effective tax rates for the periods indicated (in thousands, except percentages): Three Months Ended March 31, April 1, Provision for income taxes $ 110 $ 673 Effective tax rate (0.9 )% (2.1 )%

Company and Basis of Presenta28

Company and Basis of Presentation (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (677,320)	$ (665,584)	$ (667,357)

Significant Accounting Polici29

Significant Accounting Policies (Details)	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Largest Two Customers | Customer Concentration Risk | Revenue
Concentration Risk [Line Items]
Concentration risk, percentage	14.00%	55.00%

Significant Accounting Polici30

Significant Accounting Policies - Revenue (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Jan. 01, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Accumulated deficit	$ (677,320,000)		$ (665,584,000)	$ (667,357,000)
Revenues	99,403,000	$ 117,518,000
Total revenues	99,403,000	117,518,000
Revenue recognized	5,500,000
Unamortized balance of deferred commissions	800,000
Capitalized contract cost, amortization	100,000
Capitalized contract cost, impairment	0
United States
Disaggregation of Revenue [Line Items]
Total revenues	89,389,000	106,528,000
Caribbean
Disaggregation of Revenue [Line Items]
Total revenues	1,137,000	947,000
Canada
Disaggregation of Revenue [Line Items]
Total revenues	2,286,000	1,512,000
Europe
Disaggregation of Revenue [Line Items]
Total revenues	1,227,000	1,577,000
Other
Disaggregation of Revenue [Line Items]
Total revenues	5,364,000	$ 6,954,000
Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Accumulated deficit			$ 1,800,000
Revenues	$ 1,200,000

Significant Accounting Polici31

Significant Accounting Policies - Performance Obligations (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Accounting Policies [Abstract]
Performance obligations expected to be satisfied	$ 35.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, percentage	41.50%
Performance obligations expected to be satisfied, expected timing	1 year

Significant Accounting Polici32

Significant Accounting Policies - Adjustments (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Apr. 01, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net		$ 55,746		$ 80,883	$ 80,392
Prepaid expenses and other current assets		12,551		10,514	10,759
Other assets		1,943		1,457	759
Accrued liabilities		48,783			49,279
Total assets		270,912		296,014	295,070
Deferred revenue		14,676		12,247	13,076
Total liabilities		132,873		149,278	150,107
Accumulated deficit		(677,320)		(665,584)	(667,357)
Total liabilities and stockholders’ equity		270,912		296,014	295,070
Systems		93,291	$ 91,605
Services		6,112	25,913
Total revenue		99,403	117,518
Systems	[1]	51,633	57,373
Services	[1]	5,711	25,768
Total cost of revenue		57,344	83,141
Gross profit		42,059	34,377
Sales and marketing	[1]	19,901	22,429
Net loss		(11,736)	$ (33,325)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net		53,675			80,392
Prepaid expenses and other current assets		13,574			10,759
Other assets		1,244			759
Accrued liabilities		47,824
Total assets		269,165			295,070
Deferred revenue		16,103			13,076
Total liabilities		133,341			150,107
Accumulated deficit		(679,535)			(667,357)
Total liabilities and stockholders’ equity		269,165			$ 295,070
Systems		92,610
Services		5,573
Total revenue		98,183
Systems	[1]	51,148
Services	[1]	5,433
Total cost of revenue		56,581
Gross profit		41,602
Sales and marketing	[1]	19,886
Net loss		(12,178)
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit				1,800
Total revenue		1,200
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net		(2,071)		491
Prepaid expenses and other current assets		1,023		(245)
Other assets		(699)		698
Accrued liabilities		(959)
Total assets		(1,747)		944
Deferred revenue		1,427		(829)
Total liabilities		468		(829)
Accumulated deficit		(2,215)		1,773
Total liabilities and stockholders’ equity		(1,747)		$ 944
Systems		(681)
Services		(539)
Total revenue		(1,220)
Systems	[1]	(485)
Services	[1]	(278)
Total cost of revenue		(763)
Gross profit		(457)
Sales and marketing	[1]	(15)
Net loss		$ (442)
[1]	Includes stock-based compensation as follows: Three and Nine Months Ended March 31, 2018 and April 1, 2017; Cost of revenue: Products - $112, $116, $349, $338 ; Services - $77, $56, $200, $146; Research and development - $983, $1,326, $3,663, $3,719; Sales and marketing - $850, $1,111, $2,581, $3,323; General administrative - $735, $931, $2,521, $2,840;

Cash and Cash Equivalents (Deta

Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Apr. 01, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 42,628	$ 39,775	$ 26,318	$ 50,359
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	38,840	35,999
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 3,788	$ 3,776

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 3,788	$ 3,776
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	3,788	3,776
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	0	0
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	3,788	3,776
Money market funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	3,788	3,776
Money market funds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 0	$ 0

Balance Sheet Details - Account

Balance Sheet Details - Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Summary of accounts receivable, net
Accounts receivable	$ 56,134		$ 81,793
Allowance for doubtful accounts	(388)		(579)
Product return reserve (1)	0		(822)
Accounts receivable, net	$ 55,746	$ 80,883	$ 80,392

Balance Sheet Details - Invento

Balance Sheet Details - Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary of inventory, net
Raw materials	$ 2,244	$ 1,211
Finished goods	24,817	30,318
Total inventory	$ 27,061	$ 31,529

Balance Sheet Details - Propert

Balance Sheet Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary of property and equipment, net
Property and equipment, gross	$ 82,064	$ 80,870
Accumulated depreciation and amortization	(67,256)	(65,189)
Property and equipment, net	14,808	15,681
Test equipment
Summary of property and equipment, net
Property and equipment, gross	40,908	39,952
Computer equipment and software
Summary of property and equipment, net
Property and equipment, gross	33,206	32,175
Furniture and fixtures
Summary of property and equipment, net
Property and equipment, gross	2,744	2,714
Leasehold improvements
Summary of property and equipment, net
Property and equipment, gross	$ 5,206	$ 6,029

Balance Sheet Details - Accrued

Balance Sheet Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary of accrued liabilities
Accrued compensation and related benefits	$ 18,367	$ 15,563
Accrued warranty and retrofit	8,097	8,708
Accrued professional and consulting fees	5,349	9,604
Accrued restructuring charges	4,927	1,417
Accrued excess and obsolete inventory at contract manufacturers	3,371	2,430
Accrued non-income related taxes	1,604	1,778
Customer over payments	968	1,050
Product return reserve	959	0
Accrued insurance	717	827
Accrued freight	695	593
Accrued business events	0	1,272
Accrued other	3,729	6,037
Total accrued liabilities	$ 48,783	$ 49,279

Balance Sheet Details - Warrant

Balance Sheet Details - Warranty Reserve (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Other Commitments [Line Items]
Warranty period	3 years
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 8,708	$ 12,214
Provision for warranty and retrofit charged to cost of revenue	1,469	1,862
Utilization of reserve	(2,080)	(3,298)
Balance at end of period	$ 8,097	$ 10,778
Minimum
Other Commitments [Line Items]
Warranty period	1 year
Maximum
Other Commitments [Line Items]
Warranty period	5 years

Balance Sheet Details - Restruc

Balance Sheet Details - Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Restructuring charges	$ 5,340	$ 699
Severance and Related Benefits
Restructuring Reserve [Roll Forward]
Restructuring charges	5,300
March 2017 Restructuring
Restructuring Reserve [Roll Forward]
Restructuring charges			$ 4,200
March 2017 Restructuring | Severance and Related Benefits
Restructuring Reserve [Roll Forward]
Balance at December 31, 2017	975
Restructuring charges	4,567
Cash payments	(1,501)
Balance at March 31, 2018	4,041		975
March 2017 Restructuring | Facilities
Restructuring Reserve [Roll Forward]
Balance at December 31, 2017	442
Restructuring charges	773
Cash payments	(329)
Balance at March 31, 2018	$ 886		$ 442

Balance Sheet Details - Deferre

Balance Sheet Details - Deferred Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	$ 14,676	$ 12,247	$ 13,076
Deferred revenue, noncurrent	20,712		20,645
Deferred revenue	35,388		33,721
Products and services
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	10,675		9,125
Deferred revenue, noncurrent	493		18
Extended warranty
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	4,001		3,951
Deferred revenue, noncurrent	$ 20,219		$ 20,627

Credit Facility (Details)

Credit Facility (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017	Aug. 07, 2017
Debt Instrument [Line Items]
Line of credit	$ 30,000,000	$ 30,000,000
Silicon Valley Bank | Letter of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 30,000,000

Commitments and Contingencies -

Commitments and Contingencies - Textual (Details) ft² in Thousands, $ in Thousands	Mar. 13, 2018USD ($)ft²	Mar. 31, 2018USD ($)	Apr. 01, 2017USD ($)	Dec. 31, 2017USD ($)
Commitments and Contingencies [Line Items]
Future minimum payments due		$ 20,367
Rent expense		800	$ 900
Outstanding purchase commitments		57,400
Accrued excess and obsolete inventory at contract manufacturers		3,371		$ 2,430
San Jose, California
Commitments and Contingencies [Line Items]
Area of office | ft²	65
Term of contract	87 months
Future minimum payments due	$ 16,100
Engineering Services
Commitments and Contingencies [Line Items]
Other commitment		$ 17,500

Commitments and Contingencies44

Commitments and Contingencies - Operating Leases (Details) $ in Thousands	Mar. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Remainder of 2018	$ 2,403
2,019	3,227
2,020	2,947
2,021	2,531
2,022	2,332
Thereafter	6,927
Future minimum payments due	$ 20,367

Stockholders' Equity (Details)

Stockholders' Equity (Details) $ / shares in Units, $ in Thousands	May 17, 2017periodshares	Aug. 31, 2017shares	Mar. 31, 2018USD ($)Plan$ / sharesshares	Apr. 01, 2017USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans | Plan			2
Stock options granted (in shares)			65,000
Weighted-average grant date fair value (in dollars per share) | $ / shares			$ 6.20
Stock options exercised (in shares)			1,420
Weighted-average exercise price per share, stock options (in dollars per share) | $ / shares			$ 5.42
Unrecognized stock-based compensation expense, stock options | $			$ 3,700
Weighted-average amortization period			2 years 10 months 24 days
Taxes paid for awards vested under equity incentive plans | $			$ 5	$ 1,093
Performance Based Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)			1,165,000
Weighted-average grant date fair value (in dollars per share) | $ / shares			$ 3.43
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period			1 year 7 months 6 days
Awards granted (in shares)			27,586
Weighted-average grant date fair value per share (in dollars per share) | $ / shares			$ 7.25
Awards vested (in shares)			152,821
Unrecognized stock-based compensation expense | $			$ 6,600
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period			1 month 14 days
Unrecognized stock-based compensation expense | $			$ 200
ESPP, maximum employee payroll deduction percentage			15.00%
ESPP, maximum number of shares per employee (in shares)			2,000
ESPP, discounted purchase price percentage			85.00%
ESPP, shares purchased			0
Offering period			6 months
Shares available for issuance under the ESPP (in shares)			2,455,691
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period			10 months 24 days
Awards vested (in shares)			75,000
Unrecognized stock-based compensation expense | $			$ 100
2017 Nonqualified Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense, stock options | $			$ 1,800
Weighted-average amortization period			10 months 24 days
Maximum contribution percent (up to 25%)	25.00%
Number of offering periods | period	2
Offering period	6 months
Number of shares authorized	1,000,000
Number of shares authorized per purchase period	500,000
Executive Officer | Performance Based Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)		1,200,000

Accumulated Other Comprehensi46

Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	$ 144,963
Other comprehensive income (loss)		$ 57
Balance at end of period	138,039
Unrealized Gains and Losses on Available-for-Sale Marketable Securities
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period		(6)
Other comprehensive income (loss)		(4)
Balance at end of period		(10)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(169)	(650)
Other comprehensive income (loss)	279	61
Balance at end of period	$ 110	(589)
Total
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period		(656)
Balance at end of period		$ (599)

Product Line Divestiture (Detai

Product Line Divestiture (Details) - Clearfield, Inc. - Outdoor Cabinet Product Line - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Feb. 28, 2018	Mar. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, consideration	$ 10.4
Inventory transferred	$ 2.1
Period of new orders solicitation	15 months
Disposal group, deferred revenue	$ 1.6
Gain on disposal		$ 6.7

Net Income (Loss) Per Common 48

Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Numerator:
Net loss	$ (11,736)	$ (33,325)
Denominator:
Weighted-average common shares outstanding used to compute basic net loss per share (in shares)	51,611	49,525
Basic and diluted net loss per common share (in dollars per share)	$ (0.23)	$ (0.67)
Potentially dilutive shares, weighted average (in shares)	6,870	6,145

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 110	$ 673
Effective tax rate	(0.90%)	(2.10%)