Sycamore Networks (SCMR) 10-K 2011 FY Annual report

EXHIBIT 32.1—CERTIFICATION OF CHIEF EXECUTIVE OFFICER

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report of Sycamore Networks, Inc. (the “Company”) on Form 10-K for the year ending July 31, 2011 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Daniel E. Smith, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

(1) The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company, as of, and for the periods presented in the Report.

/s/    DANIEL E. SMITH        

Daniel E. Smith

President and Chief Executive Officer
September 21, 2011