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                                                                    EXHIBIT 23.3


                        Consent of Deloitte & Touche LLP


We consent to the incorporation by reference in this Post Effective Amendment
No. 1 to Form S-4 on Form S-8 (File No. 333-53146) of CIENA Corporation of our
report dated August 2, 2000 (December 18, 2000 as to Note 12) related to the
financial statements of Cyras Systems, Inc. appearing in the current report on
Form 8-K for CIENA Corporation filed on January 18, 2001 and our report dated
February 12, 2001 related to the financial statements of Cyras Systems, Inc.
appearing in the current report on Form 8-K for CIENA Corporation filed on April
2, 2001.


/s/ Deloitte & Touche LLP

San Jose, California

April 9, 2001