Exhibit 32.3

CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER

PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

I, Kurt Adzema, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Annual Report of Finisar Corporation (the “Company”) on Form 10-K for the year ended April 27, 2014 (the “Report”) fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934 and that the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: June 26, 2014

/s/ Kurt Adzema

Kurt Adzema

Executive Vice President, Finance and Chief Financial Officer