Exhibit 99.1

FOR IMMEDIATE RELEASE [GRAPHIC LOGO OMITTED]
SYCAMORE NETWORKS, INC.

CONTACT:

Press Inquiries
Scott Larson
Public Relations
Sycamore Networks, 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 THIRD QUARTER FISCAL YEAR 2004 FINANCIAL RESULTS

CHELMSFORD, Mass., May 11, 2004 – Sycamore Networks, Inc. (NASDAQ: SCMR), a leader in optical networking, today reported its third quarter results for the period ended April 24, 2004.

Revenue for the third quarter of fiscal 2004 was $14.7 million, compared with $10.6 million for the third quarter of fiscal 2003.

Net loss for the third quarter of fiscal 2004, on a generally accepted accounting principles (GAAP) basis, was $10.6 million or $(0.04) per share, compared with a net loss of $11.9 million, or $(0.04) per share for the third quarter of fiscal 2003. Non-GAAP net loss for the third quarter of fiscal 2004, which excludes stock-based compensation, payroll taxes on stock option exercises, and restructuring charges and related asset impairments, was $9.3 million, or $(0.03) per share, compared with a non-GAAP net loss of $12.1 million, or $(0.05) per share for the third quarter of fiscal 2003. The reconciliation between net loss on a GAAP basis and net 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 nine months of fiscal 2004 was $30.0 million, compared with $27.4 million for the first nine months of fiscal 2003.

Net loss for the first nine months of fiscal 2004, on a GAAP basis, was $35.7 million or $(0.13) per share, compared with a net loss of $45.4 million or $(0.17) per share for the first nine months of fiscal 2003. Non-GAAP net loss for the first nine months of fiscal 2004, which excludes stock-based compensation, payroll taxes on stock option exercises, and restructuring charges and related asset impairments, was $31.0 million, or $(0.11) per share, compared with a non-GAAP net loss of $41.1 million, or $(0.16) per share for the first nine months of fiscal 2003. The reconciliation between net loss on a GAAP basis and net loss on a non-GAAP basis is provided in a table immediately following the Unaudited Consolidated Statements of Operations included with this release.

“Sycamore’s third quarter financial results reflect initial purchases of our optical switches for the GIG-BE project,” stated Daniel E. Smith, Sycamore’s president and chief executive officer. “While the optical switching market environment remains difficult, we continue to work to address Sycamore’s opportunities and challenges.”

Conference Call Webcast
Sycamore plans to review its third quarter results and discuss its business outlook during a conference call today beginning at 4:30 p.m. EDT. A Webcast of the conference call, along with GAAP reconciliation information, is available to all interested parties on the Sycamore web site located at www.sycamorenet.com under the Investor Relations section. Interested investors are encouraged to log onto the broadcast at least 15 minutes prior to the call. Participating in the call will be Sycamore’s president and chief executive officer, Daniel E. Smith, and chief financial officer, Frances M. Jewels.

About Sycamore Networks
Sycamore Networks, Inc. (NASDAQ: SCMR) develops and markets optical networking products for telecommunications service providers worldwide. The Company’s products enable service providers to easily and cost-effectively transition their existing fiber optic network into an infrastructure that can provision, manage and deliver economic, high-bandwidth services to their customers. For more information, please visit www.sycamorenet.com.

Except for the historical information contained herein, we wish to caution you that certain matters discussed in this news release constitute forward-looking statements that involve risks and uncertainties. Actual results or events could differ materially from those stated or implied in forward-looking statements due to a number of factors, including but not limited to: unfavorable conditions in the telecommunications industry and the economy in general; the pursuit of strategic opportunities; the commercial success of the Company’s line of optical networking products switches; significant cost structure required to support the Company’s strategy; competition; the Company’s reliance on a limited number of customers; the Company’s ability to sell through distribution channels; variation in the Company’s quarterly results; manufacturing and sourcing risks; product performance; conducting business internationally; current and potential litigation; intellectual property rights and disputes; stock market volatility and capital market conditions; and the other factors discussed in the Company’s most recently filed 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 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 primarily in connection with the Company’s initial public offering and acquisitions.

The non-GAAP financial data is provided to enhance the user’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 as being superior to, 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)

	April 24, 2004			July 31, 2003
Assets
Current assets:
Cash and cash equivalents	$	222,721		$	250,595
Short-term investments		384,812			421,784
Accounts receivable, net		14,264			10,769
Inventories		4,017			5,117
Prepaids and other current assets		3,752			3,680
Total current assets		629,566			691,945
Property and equipment, net		10,047			14,589
Long-term investments		358,095			323,204
Other assets		2,375			2,890
Total Assets	$	1,000,083		$	1,032,628
Liabilities and Stockholders' Equity
Deferred revenue	$	6,238		$	2,677
Other current liabilities		15,188			18,350
Restructuring liabilities		14,299			19,086
Total current liabilities		35,725			40,113
Deferred revenue		672			--
Total liabilities		36,397			40,113
Common stock		273			272
Additional paid-in capital		1,738,265			1,733,476
Accumulated deficit		(771,941	)		(736,192	)
Other equity		(2,911	)		(5,041	)
Total stockholders' equity		963,686			992,515
Total Liabilities and Stockholders' Equity	$	1,000,083		$	1,032,628

Sycamore Networks, Inc.
Unaudited Consolidated Statements of Operations
(in thousands, except per share data)

	Three Months Ended						Nine Months Ended
	April 24, 2004			April 26, 2003			April 24, 2004			April 26, 2003
Revenue	$	14,718		$	10,601		$	30,034		$	27,364
Cost of revenue		9,723			8,702			19,682			26,432
Stock-based compensation and payroll tax
on stock option exercises		176			341			544			1,054
Gross profit (loss)		4,819			1,558			9,808			(122	)
Operating expenses:
Research and development		11,256			12,678			34,298			40,027
Sales and marketing		4,894			4,883			13,645			14,891
General and administrative		1,642			1,852			5,092			5,260
Stock-based compensation and
payroll tax on stock option exercises:
Research and development		521			845			2,318			2,573
Sales and marketing		255			426			797			1,558
General and administrative		309			387			1,055			1,306
Restructuring charges and
related asset impairments		--			(2,193	)		--			(2,193	)
Total operating expenses		18,877			18,878			57,205			63,422
Loss from operations		(14,058	)		(17,320	)		(47,397	)		(63,544	)
Interest and other income, net		3,485			5,426			11,648			18,171
Net loss	$	(10,573	)	$	(11,894	)	$	(35,749	)	$	(45,373	)
Diluted net loss per share	$	(0.04	)	$	(0.04	)	$	(0.13	)	$	(0.17	)
Weighted average shares used in
computing diluted net loss per share		272,652			266,638			271,642			264,640

Sycamore Networks, Inc.
Unaudited Non-GAAP Consolidated Statements of Operations (a)
(in thousands, except per share data)

	Three Months Ended April 24, 2004									Three Months Ended April 26, 2003
	GAAP Results			Adjustments			Non-GAAP Results(a)			GAAP Results			Adjustments			Non-GAAP Results (a)
Revenue	$	14,718		$	--		$	14,718		$	10,601		$	--		$	10,601
Cost of revenue		9,723			--			9,723			8,702			--			8,702
Stock-based compensation and
payroll tax on stock option exercises		176			(176	)		--			341			(341	)		--
Gross profit		4,819			176			4,995			1,558			341			1,899
Operating expenses:
Research and development		11,256			--			11,256			12,678			--			12,678
Sales and marketing		4,894			--			4,894			4,883			--			4,883
General and administrative		1,642			--			1,642			1,852			--			1,852
Stock-based compensation and
payroll tax on stock option exercises:
Research and development		521			(521	)		--			845			(845	)		--
Sales and marketing		255			(255	)		--			426			(426	)		--
General and administrative		309			(309	)		--			387			(387	)		--
Restructuring charges and
related asset impairments		--			--			--			(2,193	)		2,193			--
Total operating expenses		18,877			(1,085	)		17,792			18,878			535			19,413
Loss from operations		(14,058	)		1,261			(12,797	)		(17,320	)		(194	)		(17,514	)
Interest and other income, net		3,485			--			3,485			5,426			--			5,426
Net loss	$	(10,573	)	$	1,261		$	(9,312	)	$	(11,894	)	$	(194	)	$	(12,088	)
Diluted net loss per share	$	(0.04	)				$	(0.03	)	$	(0.04	)				$	(0.05	)
Weighted average shares used in   computing diluted net loss per share		272,652						272,652			266,638						266,638

(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 and payroll taxes on stock option exercises included in gross profit and operating expenses, and restructuring charges and related asset impairments.

Sycamore Networks, Inc.
Consolidated Statements of Operations (a)
(in thousands, except per share data)

	Nine Months Ended April 24, 2004									Nine Months Ended April 26, 2003
	GAAP Results			Adjustments			Non-GAAP Results(a)			GAAP Results			Adjustments			Non-GAAP Results (a)
Revenue	$	30,034		$	--		$	30,034		$	27,364		$	--		$	27,364
Cost of revenue		19,682			--			19,682			26,432			--			26,432
Stock-based compensation and
payroll tax on stock option exercises		544			(544	)		--			1,054			(1,054	)		--
Gross profit (loss)		9,808			544			10,352			(122	)		1,054			932
Operating expenses:
Research and development		34,298			--			34,298			40,027			--			40,027
Sales and marketing		13,645			--			13,645			14,891			--			14,891
General and administrative		5,092			--			5,092			5,260			--			5,260
Stock-based compensation and
payroll tax on stock option exercises:
Research and development		2,318			(2,318	)		--			2,573			(2,573	)		--
Sales and marketing		797			(797	)		--			1,558			(1,558	)		--
General and administrative		1,055			(1,055	)		--			1,306			(1,306	)		--
Restructuring charges and
related asset impairments		--			--			--			(2,193	)		2,193			--
Total operating expenses		57,205			(4,170	)		53,035			63,422			(3,244	)		60,178
Loss from operations		(47,397	)		4,714			(42,683	)		(63,544	)		4,298			(59,246	)
Interest and other income, net		11,648			--			11,648			18,171			--			18,171
Net loss	$	(35,749	)	$	4,714		$	(31,035	)	$	(45,373	)	$	4,298		$	(41,075	)
Diluted net loss per share	$	(0.13	)				$	(0.11	)	$	(0.17	)				$	(0.16	)
Weighted average shares used in    computing diluted net loss per share		271,642						271,642			264,640						264,640

(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 and payroll taxes on stock option exercises included in gross profit (loss) and operating expenses, and restructuring charges and related asset impairments.