Exhibit 99.1

CONTACT: PressInquiries ScottLarson PublicRelations SycamoreNetworks, Inc. 978-250-3433 scott.larson@sycamorenet.com Investor Inquiries Terry Adams Investor Relations Sycamore Networks, Inc. 978-250-3460 investor.info@sycamorenet.com

SYCAMORE NETWORKS, INC. REPORTS SECOND QUARTER FISCAL YEAR 2006

FINANCIAL RESULTS

CHELMSFORD, Mass., February 21, 2006 – Sycamore Networks, Inc. (NASDAQ: SCMR), a leader in optical networking, today reported its second quarter results for the period ended January 28, 2006.

Revenue for the second quarter of fiscal 2006 was $20.8 million, compared with $14.9 million for the second quarter of fiscal 2005.

Net income for the second quarter of fiscal 2006, on a generally accepted accounting principles (GAAP) basis, was $5.0 million, or $0.02 per fully diluted share, compared with a net loss of $5.4 million, or $(0.02) per fully diluted share for the second quarter of fiscal 2005. Non-GAAP net income for the second quarter of fiscal 2006, which excludes stock-based compensation expense and a litigation settlement, was $7.1 million, or $0.03 per fully diluted share, compared with a non-GAAP net loss of $5.0 million, or $(0.02) per fully diluted share for the second quarter of fiscal 2005. 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 Consolidated Statements of Operations included with this release.

Revenue for the first six months of fiscal 2006 was $48.1 million, compared with $29.1 million for the first six months of fiscal 2005.

Net income for the first six months of fiscal 2006, on a GAAP basis, was $11.9 million or $0.04 per fully diluted share, compared with a net loss of $13.2 million, or $(0.05) per fully diluted share for the first six months of fiscal 2005. Non-GAAP net income for the first six months of fiscal 2006, which excludes stock-based compensation expense and a litigation settlement, was $15.4 million, or $0.05 per fully diluted share, compared with a non-GAAP net loss of $12.2 million, or $(0.04) per fully diluted share for the first six months of fiscal 2005. 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 Consolidated Statements of Operations included with this release.

“Q2 was another solid quarter for Sycamore. We continue to maintain strong margins, carefully manage our expenses, improve our operating performance and generate cash from operations,” said Daniel E. Smith, president and chief executive officer. “As IP-based voice, video and data applications drive increased demand for reliable and agile bandwidth in backbone networks, our data-optimized optical switching solutions continue to deliver unique value to our customers.”

About Sycamore Networks

Sycamore Networks, Inc. (NASDAQ: SCMR) is a leading provider of intelligent optical switching products for telecommunications service providers worldwide. The Company’s products form the reliable foundation for some of the world’s most respected and innovative communications networks. Sycamore’s fully integrated edge-to-core optical switching solutions enable network operators to efficiently and cost-effectively provision and manage optical network capacity to support a wide range of voice, video and data services. For more information, please visit www.sycamorenet.com.

We wish to caution you that certain matters discussed in this news release constitute forward-looking statements that involve risks and uncertainties. Readers are cautioned that actual results or events could differ materially from those stated or implied in forward-looking statements. These risks and uncertainties include, but are not limited to, additional actions and findings that may result from the restatement of previously issued financial statements, the Company’s reliance on a limited number of customers, the significant cost structure required to support the Company’s strategy, variation of the Company’s quarterly results and competition in the telecommunications industry. Certain additional risks are set forth in more detail in the section entitled Factors that May Affect Future Results in Management Discussion and Analysis of Financial Conditions and Results of Operations in the Company’s most recently filed Form 10-K, Form 10-Q and the other reports filed by the Company from time to time 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.

Use of Non-GAAP Financial Measures

The Company provides non-GAAP financial data in addition to providing financial results in accordance with 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 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 stock option 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 because such charges are associated with past events and are not related to current operations. 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 losses, cash flows, or other measures of financial performance prepared in accordance with GAAP.

Sycamore Networks, Inc.

Unaudited Condensed Consolidated Balance Sheets

(in thousands)

Assets	January 28, 2006			July 31, 2005
Current assets
Cash and cash equivalents	$	691,236		$	508,281
Short-term investments		232,666			446,258
Accounts receivable, net		10,490			8,384
Inventories		4,100			5,445
Prepaids and other current assets		4,329			3,812
Total current assets		942,821			972,180
Property and equipment, net		9,103			8,437
Long-term investments		41,877			496
Other assets		885			950
Total Assets	$	994,686		$	982,063
Liabilities and Stockholders’ Equity
Current liabilities
Deferred revenue	$	3,816		$	8,700
Other current liabilities		18,497			23,779
Restructuring liabilities		6,925			8,455
Total current liabilities		29,238			40,934
Long term deferred revenue		2,350			1,584
Total liabilities		31,588			42,518
Common stock		278			276
Additional paid-in capital		1,790,352			1,780,243
Accumulated deficit		(826,673	)		(838,533	)
Other equity		(859	)		(2,441	)
Total stockholders’ equity		963,098			939,545
Total Liabilities and Stockholders’ Equity	$	994,686		$	982,063

Sycamore Networks, Inc.

Unaudited Consolidated Statements of Operations

(in thousands, except per share data)

	Three Months Ended						Six Months Ended
	January 28,			January 29,			January 28,			January 29,
	2006			2005			2006			2005
Revenue	$	20,835		$	14,892		$	48,133		$	29,107
Cost of revenue		10,397			8,402			23,338			16,942
Stock-based compensation		332			78			655			202
Gross profit		10,106			6,412			24,140			11,963
Operating expenses:
Research and development		7,377			11,217			15,090			22,889
Sales and marketing		2,401			3,011			5,038			6,155
General and administrative		2,122			1,932			5,020			4,180
Stock-based compensation:
Research and development		511			229			1,136			516
Sales and marketing		251			32			493			81
General and administrative		303			45			579			257
Litigation settlement		750			—			750			—
Total operating expenses		13,715			16,466			28,106			34,078
Loss from operations		(3,609	)		(10,054	)		(3,966	)		(22,115	)
Interest and other income, net		8,726			4,672			16,156			8,870
Income (loss) before income taxes		5,117			(5,382	)		12,190			(13,245	)
Income tax expense		111			—			330			—
Net income (loss)	$	5,006		$	(5,382	)	$	11,860		$	(13,245	)
Net income (loss) per share:
Basic	$	0.02		$	(0.02	)	$	0.04		$	(0.05	)
Diluted	$	0.02		$	(0.02	)	$	0.04		$	(0.05	)
Weighted average shares outstanding:
Basic		277,435			274,963			276,854			274,497
Diluted		281,036			274,963			280,084			274,497

Sycamore Networks, Inc.

Unaudited Non-GAAP Consolidated Statements of Operations (a)

(in thousands, except per share data)

	Three Months Ended January 28, 2006
	GAAP Results			Adjustments			Non-GAAP Results (a)
Revenue	$	20,835		$	—		$	20,835
Cost of revenue		10,397			—			10,397
Stock-based compensation		332			(332	)		—
Gross profit		10,106			332			10,438
Operating expenses:
Research and development		7,377			—			7,377
Sales and marketing		2,401			—			2,401
General and administrative		2,122			—			2,122
Stock-based compensation:
Research and development		511			(511	)		—
Sales and marketing		251			(251	)		—
General and administrative		303			(303	)		—
Litigation settlement		750			(750	)		—
Total operating expenses		13,715			(1,815	)		11,900
Loss from operations		(3,609	)		2,147			(1,462	)
Interest and other income, net		8,726			—			8,726
Income before income taxes		5,117			2,147			7,264
Income tax expense		111			47			158
Net income	$	5,006		$	2,100		$	7,106
Net income per share:
Basic	$	0.02					$	0.03
Diluted	$	0.02					$	0.03
Weighted average shares outstanding:
Basic		277,435						277,435
Diluted		281,036						281,036

(a) These Unaudited non-GAAP Consolidated Statements of Operations are for informational purposes only and are not presented in accordance with GAAP. The adjustments necessary to provide a direct reconciliation of the non-GAAP to the GAAP basis consolidated statements of operations exclude stock-based compensation expense and a litigation settlement.

Sycamore Networks, Inc.

Unaudited Non-GAAP Consolidated Statements of Operations (a)

(in thousands, except per share data)

	Three Months Ended January 29, 2005
	GAAP Results			Adjustments			Non-GAAP Results (a)
Revenue	$	14,892		$	—		$	14,892
Cost of revenue		8,402			—			8,402
Stock-based compensation		78			(78	)		—
Gross profit		6,412			78			6,490
Operating expenses:
Research and development		11,217			—			11,217
Sales and marketing		3,011			—			3,011
General and administrative		1,932			—			1,932
Stock-based compensation:
Research and development		229			(229	)		—
Sales and marketing		32			(32	)		—
General and administrative		45			(45	)		—
Total operating expenses		16,466			(306	)		16,160
Loss from operations		(10,054	)		384			(9,670	)
Interest and other income, net		4,672			—			4,672
Net loss	$	(5,382	)	$	384		$	(4,998	)
Net loss per share:
Basic	$	(0.02	)				$	(0.02	)
Diluted	$	(0.02	)				$	(0.02	)
Weighted average shares outstanding:
Basic		274,963						274,963
Diluted		274,963						274,963

(a) These Unaudited non-GAAP Consolidated Statements of Operations are for informational purposes only and are not presented in accordance with GAAP. The adjustments necessary to provide a direct reconciliation of the non-GAAP to the GAAP basis consolidated statements of operations exclude stock-based compensation expense.

Sycamore Networks, Inc.

Unaudited Non-GAAP Consolidated Statements of Operations (a)

(in thousands, except per share data)

	Six Months Ended January 28, 2006
	GAAP Results			Adjustments			Non-GAAP Results (a)
Revenue	$	48,133		$	—		$	48,133
Cost of revenue		23,338			—			23,338
Stock-based compensation		655			(655	)		—
Gross profit		24,140			655			24,795
Operating expenses:
Research and development		15,090			—			15,090
Sales and marketing		5,038			—			5,038
General and administrative		5,020			—			5,020
Stock-based compensation:
Research and development		1,136			(1,136	)		—
Sales and marketing		493			(493	)		—
General and administrative		579			(579	)		—
Litigation settlement		750			(750	)		—
Total operating expenses		28,106			(2,958	)		25,148
Loss from operations		(3,966	)		3,613			(353	)
Interest and other income, net		16,156			—			16,156
Income before income taxes		12,190			3,613			15,803
Income tax expense		330			98			428
Net income	$	11,860		$	3,515		$	15,375
Net income per share:
Basic	$	0.04					$	0.06
Diluted	$	0.04					$	0.05
Weighted average shares outstanding:
Basic		276,854						276,854
Diluted		280,084						280,084

(a) These Unaudited non-GAAP Consolidated Statements of Operations are for informational purposes only and are not presented in accordance with GAAP. The adjustments necessary to provide a direct reconciliation of the non-GAAP to the GAAP basis consolidated statements of operations exclude stock-based compensation expense and a litigation settlement.

Sycamore Networks, Inc.

Unaudited Non-GAAP Consolidated Statements of Operations (a)

(in thousands, except per share data)

	Six Months Ended January 29, 2005
	GAAP Results			Adjustments			Non-GAAP Results (a)
Revenue	$	29,107		$	—		$	29,107
Cost of revenue		16,942			—			16,942
Stock-based compensation		202			(202	)		—
Gross profit		11,963			202			12,165
Operating expenses:
Research and development		22,889			—			22,889
Sales and marketing		6,155			—			6,155
General and administrative		4,180			—			4,180
Stock-based compensation:
Research and development		516			(516	)		—
Sales and marketing		81			(81	)		—
General and administrative		257			(257	)		—
Total operating expenses		34,078			(854	)		33,224
Loss from operations		(22,115	)		1,056			(21,059	)
Interest and other income, net		8,870			—			8,870
Net loss	$	(13,245	)	$	1,056		$	(12,189	)
Net loss per share:
Basic	$	(0.05	)				$	(0.04	)
Diluted	$	(0.05	)				$	(0.04	)
Weighted average shares outstanding:
Basic		274,497						274,497
Diluted		274,497						274,497

(a) These Unaudited non-GAAP Consolidated Statements of Operations are for informational purposes only and are not presented in accordance with GAAP. The adjustments necessary to provide a direct reconciliation of the non-GAAP to the GAAP basis consolidated statements of operations exclude stock-based compensation expense.