The amount of the company's cash, cash equivalents, short-term investments and restricted cash.

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Represents the number of credit facilities available under an arrangement.

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- Definition

The number of customers used to calculate the concentration risk percentage.

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- Definition

The planned period for the implementation of the restructuring plan.

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The amount of the company's working capital used to fund operations.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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No definition available.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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- Definition

Amount of cash inflow (outflow) from operating activities, excluding discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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The net result for the period of deducting operating expenses from operating revenues.

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No definition available.

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The cumulative amount of the reporting entity's undistributed earnings or deficit.

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Amount of unrecognized tax benefits.

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Basis of presentation and significant accounting policies - (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($) customer	Jun. 30, 2016 USD ($) customer	Jun. 30, 2017 USD ($) customer item	Jun. 30, 2016 USD ($) customer	Dec. 31, 2016 USD ($) customer	Jul. 31, 2017 USD ($)	Jan. 01, 2017 USD ($)
Concentration Risk [Line Items]
Working capital	$ 102,800,000		$ 102,800,000
Cash, cash equivalents, short-term investments and restricted cash	79,000,000		79,000,000
Operating losses	(9,701,000)	$ 2,866,000	(21,575,000)	$ 7,568,000
Cash flows from operations			(16,496,000)	$ 23,178,000
Accumulated deficit	(319,541,000)		$ (319,541,000)		$ (298,678,000)
Restructuring plan implementation period			1 year
China
Concentration Risk [Line Items]
Number of credit facilities \| item			3
Unused part of credit facility	$ 20,800,000		$ 20,800,000
Expiring in third quarter of 2017
Concentration Risk [Line Items]
Number of credit facilities \| item			2
Must be extended to fund planned operations and expenditures over next year [Member]
Concentration Risk [Line Items]
Number of credit facilities \| item			1
Accounting Standards Update 2016-09
Concentration Risk [Line Items]
Previously unrecognized tax benefits							$ 8,600,000
Impact of adoption of new accounting policy							$ 0
Accounts Receivable [Member]
Concentration Risk [Line Items]
Number of customers \| customer			2		3
Huawei Technologies [Member] \| Revenue [Member]
Concentration Risk [Line Items]
Percentage of concentration of credit risk	37.00%	45.00%	39.00%	49.00%
Ciena Corporation [Member] \| Revenue [Member]
Concentration Risk [Line Items]
Percentage of concentration of credit risk	19.00%	16.00%	16.00%	16.00%
Company Top Ten Customers [Member] \| Revenue [Member]
Concentration Risk [Line Items]
Percentage of concentration of credit risk	89.00%	91.00%	89.00%	91.00%
Number of customers \| customer	10	10	10	10
Customer One [Member] \| Accounts Receivable [Member]
Concentration Risk [Line Items]
Percentage of concentration of credit risk			36.00%		42.00%
Customer Two [Member] \| Accounts Receivable [Member]
Concentration Risk [Line Items]
Percentage of concentration of credit risk			12.00%		12.00%
Customer Three [Member] \| Accounts Receivable [Member]
Concentration Risk [Line Items]
Percentage of concentration of credit risk					12.00%
Comerica \| United States
Concentration Risk [Line Items]
Credit facility, maximum amount	$ 30,000,000		$ 30,000,000
Line of credit facility	20,000,000		20,000,000
CITIC Bank \| China
Concentration Risk [Line Items]
Credit facility, maximum amount	$ 39,200,000		$ 39,200,000
CITIC Bank \| China \| Subsequent Event
Concentration Risk [Line Items]
Line of credit facility						$ 17,000,000