Exhibit 99.1

CONTACT:
Robert Travis	Scott Larson
Investor Relations	Press Inquiries
Sycamore Networks, Inc.	Sycamore Networks, Inc.
978-250-3432	978-250-3433
bob.travis@sycamorenet.com	scott.larson@sycamorenet.com

SYCAMORE NETWORKS, INC. REPORTS THIRD QUARTER FISCAL YEAR

2009 FINANCIAL RESULTS

CHELMSFORD, Mass., June 4, 2009 – Sycamore Networks, Inc. (NASDAQ: SCMR), a leader in intelligent bandwidth management solutions for fixed line and mobile network operators worldwide, today reported its financial results for the third quarter ended April 25, 2009. Revenue for the third quarter of fiscal 2009 was $23.0 million, compared with $21.0 million for the third quarter of fiscal 2008.

Net loss for the third quarter of fiscal 2009, on a generally accepted accounting principles (“GAAP”) basis, was $2.7 million, or $0.01 per share, compared with net loss of $2.7 million, or $0.01 per share for the third quarter of fiscal 2008. Non-GAAP net loss for the third quarter of fiscal 2009 was $1.2 million, or $0.00 per share, compared with non-GAAP net loss of $0.4 million, or $0.00 per share for the third quarter of fiscal 2008. The reconciliation between net income (loss) on a GAAP basis and net income (loss) on a non-GAAP basis is provided in a table immediately following the Unaudited Non-GAAP Consolidated Statements of Operations included with this release.

Net loss for the first nine months of fiscal 2009, on a GAAP basis, was $18.6 million or $0.07 per share, compared with net income of $14.0 million or $0.05 per fully diluted share for the first nine months of fiscal 2008. Non-GAAP net loss for the first nine months of fiscal 2009 was $13.0 million, or $0.05 per share, compared with non-GAAP net income of $21.6 million, or $0.08 per fully diluted share for the first nine months of fiscal 2008. The reconciliation between net income (loss) on a GAAP basis and net income (loss) on a non-GAAP basis is provided in a table immediately following the Unaudited Non-GAAP Consolidated Statements of Operations included with this release.

“Sycamore’s third quarter results indicate that we continue to operate in a challenging business environment,” said Daniel E. Smith, president and chief executive officer. “We remain steadfast in our commitment to meeting the needs of our customers and prospects. We are confident in our ability to advance our solutions with innovative technology and deliver the level of excellence in customer support that has been a hallmark of the company.”

About Sycamore Networks

Sycamore Networks, Inc. (NASDAQ: SCMR) is a leading provider of intelligent bandwidth management solutions for fixed line and mobile network operators worldwide. From multiservice access networks to the optical core, Sycamore products enable network operators to lower overall network costs, increase operational efficiencies, and rapidly deploy new revenue-generating services. Sycamore’s global customer base includes Tier 1 service providers, government agencies, and utility companies. For more information, please visit www.sycamorenet.com.

Use of Non-GAAP Financial Measures

The Company provides non-GAAP financial data in addition to providing financial results in accordance with generally accepted accounting principles (GAAP). These measures are not in accordance with, or an alternative for GAAP, and may be different from non-GAAP measures used by other companies. The Company believes that the items excluded from the non-GAAP results have one or more of the following characteristics: their magnitude and timing is largely outside of the Company’s control; they are unrelated to the ongoing operation of the business in the ordinary course; they are unusual, and the Company does not expect them to occur in the ordinary course of business; or they are non-operational, non-cash expenses involving equity grants.

The non-GAAP financial data is provided to enhance the reader’s overall understanding of the Company’s current financial performance and its prospects for the future. Specifically, the Company believes the non-GAAP results provide useful information to both management and investors by excluding certain expense and income items that the Company believes are not indicative of the Company’s core operating results. In addition, since the Company has historically reported non-GAAP results to the investment community, the Company believes the inclusion of non-GAAP numbers provides consistency in its financial reporting. Further, these non-GAAP results are one of the primary indicators management uses for planning and forecasting in future periods. The non-GAAP financial data should be considered in addition to, not as a substitute for or a more appropriate indicator of, operating results, cash flows, or other measures of financial performance prepared in accordance with GAAP.

We wish to caution you that certain matters discussed in this news release constitute forward-looking statements regarding future events that involve risks and uncertainties. Readers are cautioned that actual results or events could differ materially from those stated or implied in the forward-looking statements. Other risks and uncertainties include, but are not limited to, actions, inquiries and findings that may result from certain stock option matters, including the restatement of previously issued financial statements; the Company’s reliance on a limited number of customers; variation in the Company’s quarterly results; industry pricing pressures and the high cost of product development required to remain competitive and keep pace with evolving features and technologies desired by customers; the consolidation of both suppliers and customers in the telecommunications marketplace and general economic conditions. Certain additional risks are set forth in more detail in the section entitled “Risk Factors” in the Company’s most recent Quarterly Report on Form 10-Q and Annual Report on Form 10-K filed by the Company with the Securities and Exchange Commission. The Company disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future results or otherwise.

Sycamore Networks, Inc.

Unaudited Condensed Consolidated Balance Sheets

(in thousands)

	April 25, 2009			July 31, 2008
Assets
Current assets:
Cash and cash equivalents	$	423,442		$	499,922
Short-term investments		290,769			321,173
Accounts receivable, net		13,290			8,779
Inventories		19,137			23,750
Prepaids and other current assets		2,260			2,847
Total current assets		748,898			856,471
Property and equipment, net		16,791			20,437
Long-term investments		217,572			120,739
Purchased intangibles, net		3,021			4,000
Goodwill		20,334			20,334
Other assets		455			482
Total Assets	$	1,007,071		$	1,022,463
Liabilities and Stockholders’ Equity
Current liabilities:
Deferred revenue	$	11,487		$	14,300
Other current liabilities		13,977			14,043
Total current liabilities		25,464			28,343
Long term deferred revenue		4,868			4,841
Long term liability		1,901			1,904
Total liabilities		32,233			35,088
Common stock		284			284
Additional paid-in capital		2,038,454			2,034,818
Accumulated deficit		(1,066,425	)		(1,047,783	)
Other equity		2,525			56
Total stockholders’ equity		974,838			987,375
Total Liabilities and Stockholders’ Equity	$	1,007,071		$	1,022,463

Sycamore Networks, Inc.

Unaudited Consolidated Statements of Operations

(in thousands, except per share data)

	Three Months Ended						Nine Months Ended
	April 25, 2009			April 26, 2008			April 25, 2009			April 26, 2008
Revenue	$	22,983		$	20,966		$	50,112		$	100,403
Cost of revenue		10,413			11,248			28,275			51,625
Gross profit		12,570			9,718			21,837			48,778
Operating expenses:
Research and development		13,042			12,232			37,409			34,486
Sales and marketing		3,648			4,980			11,366			15,489
General and administrative		2,320			2,901			5,573			12,367
Restructuring & related impairment		—			471			817			2,368
Total operating expenses		19,010			20,584			55,165			64,710
Loss from operations		(6,440	)		(10,866	)		(33,328	)		(15,932	)
Interest and other income, net		3,831			8,614			14,851			30,908
Income (loss) before income taxes		(2,609	)		(2,252	)		(18,477	)		14,976
Income tax expense		123			491			165			1,012
Net income (loss)	$	(2,732	)	$	(2,743	)	$	(18,642	)	$	13,964
Net income (loss) per share:
Basic	$	(0.01	)	$	(0.01	)	$	(0.07	)	$	0.05
Diluted	$	(0.01	)	$	(0.01	)	$	(0.07	)	$	0.05
Weighted average shares outstanding:
Basic		283,601			283,164			283,520			282,197
Diluted		283,601			283,164			283,520			284,333

Sycamore Networks, Inc.

Unaudited Non-GAAP Consolidated Statements of Operations

(in thousands, except per share data)

	Three Months Ended						Nine Months Ended
	April 25, 2009			April 26, 2008			April 25, 2009			April 26, 2008
Revenue	$	22,983		$	20,966		$	50,112		$	100,403
Cost of revenue		10,273			11,077			27,507			51,180
Gross profit		12,710			9,889			22,605			49,223
Operating expenses:
Research and development		12,533			11,751			35,892			33,234
Sales and marketing		3,376			4,683			10,443			14,678
General and administrative		1,757			1,929			3,931			9,458
Total operating expenses		17,666			18,363			50,266			57,370
Loss from operations		(4,956	)		(8,474	)		(27,661	)		(8,147	)
Interest and other income, net		3,831			8,614			14,851			30,908
Income (loss) before income taxes		(1,125	)		140			(12,810	)		22,761
Income tax expense		123			518			165			1,187
Net income (loss)	$	(1,248	)	$	(378	)	$	(12,975	)	$	21,574
Net income (loss) per share:
Basic	$	(0.00	)	$	(0.00	)	$	(0.05	)	$	0.08
Diluted	$	(0.00	)	$	(0.00	)	$	(0.05	)	$	0.08
Weighted average shares outstanding:
Basic		283,601			283,164			283,520			282,197
Diluted		283,601			283,164			283,520			284,333

Sycamore Networks, Inc.

Reconciliation of GAAP to Non-GAAP Net Income

(in thousands, except per share data)

	Three Months Ended						Nine Months Ended
	April 25, 2009			April 26, 2008			April 25, 2009			April 26, 2008
GAAP net income (loss)	$	(2,732	)	$	(2,743	)	$	(18,642	)	$	13,964
Stock-based compensation expense:
Cost of revenue		140			171			452			445
Research and development		509			481			1,517			1,252
Sales and marketing		272			297			923			811
General and administrative		231			245			663			712
Total stock based compensation expense		1,152			1,194			3,555			3,220
Amortization of purchased intangible assets		332			727			979			2,197
Restructuring and other asset impairments:
Operating expense		—			471			817			2,368
Cost of revenue		—			—			316			—
Tax effect		—			(27	)		—			(175	)
Non-GAAP net income (loss)	$	(1,248	)	$	(378	)	$	(12,975	)	$	21,574