Exhibit 23.1

                      CONSENT OF INDEPENDENT ACCOUNTANTS

          We hereby consent to the use in this Registration Statement on Form
S-1 of our report dated August 23, 1999, except for the information presented in
the third paragraph of Note 6 for which the date is February 11, 2000, relating
to the financial statements of Sycamore Networks, Inc., which appears in such
Registration Statement. We also consent to the references to us under the
headings "Experts" and "Selected Consolidated Financial Data" in such
Registration Statement.


/s/ PricewaterhouseCoopers LLP
Boston, Massachusetts
February 17, 2000