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 ended July 31, 2016 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, David Guerrera, 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/ DAVID GUERRERA

David Guerrera

Principal Executive Officer, President and Secretary

October 28, 2016

SYCAMORE NETWORKS INC 10-K