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Exhibit 3.6

                            CERTIFICATE OF AMENDMENT
                                       OF
                   THIRD RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                                CIENA CORPORATION

       It is hereby certified that:

       1.     The name of the corporation is CIENA Corporation (hereinafter
called the "Corporation"). The Corporation was originally incorporated under the
name "Hydralite Incorporated", and the date of filing of the original
Certificate of Incorporation of the Corporation with the Secretary of State of
the State of Delaware is November 2, 1992. A Restated Certificate of
Incorporation was filed thereafter on April 8, 1994 (the "First Restated
Certificate"); a Second Restated Certificate was filed thereafter on December
20, 1994 (the "Second Restated Certificate of Incorporation"); a Third Restated
Certificate of Incorporation was filed thereafter on December 20, 1995 (the
"Third Restated Certificate of Incorporation"); a Certificate of Amendment to
the Third Restated Certificate of Incorporation was filed thereafter on December
9, 1996; a Certificate of Designation was filed thereafter on January 12, 1998,
and a Certificate of Amendment to the Third Restated Certificate of
Incorporation was filed thereafter on March 13, 1998.

       2.     The board of directors of the Corporation, in a meeting of the
Board of Directors held on January 13, 2000, adopted a resolution declaring it
advisable that the Third Restated Certificate of Incorporation of the
Corporation be amended by striking out the first paragraph of Article Fourth
thereof and substituting in lieu thereof the following new paragraph:

              "FOURTH: The Corporation shall have the authority to issue two (2)
              classes of shares to be designated respectively "Preferred Stock"
              and "Common Stock." The total number of shares of stock that the
              Corporation shall have the authority to issue is Four Hundred
              Eighty Million (480,000,000) shares of capital stock, par value
              $0.01 per share. The total number of shares of Preferred Stock
              that the Corporation shall have authority to issue is Twenty
              Million (20,000,000), par value $0.01 per share. The total number
              of shares of Common Stock which the Corporation shall have the
              authority to issue is Four Hundred Sixty Million (460,000,000),
              par value $0.01 per share."

       3.     The board of directors of the Corporation, in a meeting of the
Board of Directors held on January 13, 2000, has adopted a resolution directing
that the aforesaid amendment to the Third Restated Certificate of Incorporation
of the Corporation be presented to the stockholders of the Corporation at their
next annual meeting for their consideration.

       4.     Holders of the majority of the outstanding stock of the
Corporation entitled to vote thereon at the Annual Meeting of Stockholders held
on March 16, 2000 at 3:00 p.m. have approved and adopted the aforesaid amendment
to the Third Restated Certificate of Incorporation.

       5.     The aforesaid amendment to the certificate of Third Restated
Certificate of Incorporation was duly adopted in accordance with the provisions
of Section 242 of the General Corporation Law of the State of Delaware.

       IN WITNESS WHEREOF, CIENA Corporation has caused this certificate to be
signed by Patrick H. Nettles, its President and Chief Executive Officer, this
______ th day of March, 2000.

                                     CIENA Corporation

                                     By:  /s/ PATRICK H. NETTLES
                                          ------------------------------------
                                          Patrick H. Nettles
                                          President and Chief Executive Officer


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