EXHIBIT 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statements on Form S-8 (Nos. 333-45502, 333-90839, 333-51486, 333-52562 and 333-104353) of Sycamore Networks, Inc. of our report dated September 25, 2007 relating to the financial statements and the effectiveness of internal control over financial reporting, which appears in this Form 10-K.

PricewaterhouseCoopers LLP

Boston, Massachusetts

September 25, 2007