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     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON APRIL 10, 2001

                                                      Registration No. 333-53146

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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                            ------------------------

                          POST EFFECTIVE AMENDMENT NO.1

                                       TO

                                    FORM S-4

                                       ON

                                    FORM S-8

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                            ------------------------

                                CIENA CORPORATION
             (Exact name of registrant as specified in its charter)

                                    Delaware
                         (State or other jurisdiction of
                         incorporation or organization)

                                   23-2725311
                  --------------------------------------------
                      (I.R.S. Employer Identification No.)



                               1201 Winterson Road
                            Linthicum, Maryland 21090
                                 (410) 865-8500
                                 --------------
                   (Address, including zip code, and telephone
             number, including area code, of registrant's principal
                               executive offices)

                            ------------------------
                      Cyras Systems, Inc. 1998 Stock Plan
                           (Full title of the Plan)

                          -------------------------
                           Michael O. McCarthy III
             Senior Vice President, General Counsel and Secretary
                              CIENA Corporation
                             1201 Winterson Road
                          Linthicum, Maryland 21090
                                (410) 865-8500

 (Name, address and telephone number, including area code, of agent for service)

                                   Copy to:
                              Michael J. Silver
                              Amy Bowerman Freed
                            Hogan & Hartson L.L.P.
                           111 South Calvert Street
                          Baltimore, Maryland 21202
                                (410) 659-2700

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                               EXPLANATORY NOTE

The Registrant is filing this Post Effective Amendment No. 1 to Form S-4 on Form
S-8 to register the issuance of 2,015,783 shares of common stock under the Cryas
Systems, Inc. 1998 Stock Option Plan that the Registrant has assumed pursuant
to the Agreement and Plan of Merger dated December 18, 2000 between the
Registrant, Cyras Systems, Inc., a Delaware corporation, and CO Acquisition
Corp., a wholly-owned subsidiary of the Registrant, pursuant to which Cyras
Systems became a wholly-owned subsidiary of the Registrant effective
March 29, 2001.

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                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS


               The documents containing the information specified in Part I will
be sent or given to employees as specified by Rule 428(b)(1) of the Securities
Act of 1933 (the "Securities Act"). In accordance with the instructions to Part
I of Form S-8, such documents will not be filed with the Securities and Exchange
Commission (the "Commission"). These documents and the documents incorporated by
reference pursuant to Item 3 of Part II of this registration statement, taken
together, constitute a prospectus that meets the requirements of Section 10(a)
of the Securities Act.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.        INCORPORATION OF DOCUMENTS BY REFERENCE.

               CIENA Corporation (the "Company") hereby incorporates by
reference into this registration statement the following documents filed by it
with the Commission:

               (a)    The Registrant's Form 10-K for the fiscal year ended
                      October 31, 2000 and filed December 7, 2000, as amended on
                      January 18, 2001;

               (b)    The Registrant's Form 10-Q for the fiscal quarter ended
                      January 31, 2001 and filed February 15, 2001;

               (c)    The Registrant's current reports on Form 8-K filed on
                      January 18, 2001 and April 2, 2001;

               (d)    All reports filed with the Commission pursuant to Section
                      13(a) or 15(d) of the Securities Exchange Act of 1934, as
                      amended (the "Exchange Act"), since October 31, 2000; and

               (e)    The description of the Company's Common Stock, $.01 par
                      value per share ("Common Stock"), contained in the
                      Registrant's Registration Statement on Form 8-A filed with
                      the Commission on January 13, 1997, including all
                      amendments and reports filed under Section 13(a) or 15(d)
                      of the Exchange Act for purposes of updating the
                      description of Common Stock.

               In addition, all documents and reports filed by the Company
subsequent to the date hereof pursuant to Sections 13(a), 13(c), 14, and 15(d)
of the Exchange Act, prior to the filing of a post-effective amendment to this
registration statement which indicates that all securities offered have been
sold or which deregisters all securities remaining unsold, shall be deemed to be
incorporated by reference in this registration statement and to be part hereof
from the date of filing of such documents or reports. Any statement contained in
a document incorporated or deemed to be incorporated by reference herein shall
be deemed to be modified or superseded for purposes of this registration
statement to the extent that a statement contained herein or in any other
subsequent filed document which also is or is deemed to be incorporated by
reference herein modifies or supersedes such statement. Any such statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part of this registration statement.

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ITEM 4.        DESCRIPTION OF SECURITIES.

               Not applicable (the Common Stock is registered under Section
12(g) of the Exchange Act).

ITEM 5.        INTERESTS OF NAMED EXPERTS AND COUNSEL.

               Not applicable.

ITEM 6.        INDEMNIFICATION OF DIRECTORS AND OFFICERS.

               Section 145 of the Delaware General Corporation Law permits
indemnification of officers, directors and other corporate agents under certain
circumstances and subject to certain limitations. The Registrant's Third Amended
and Restated Certificate of Incorporation and bylaws provide that the Registrant
shall indemnify its directors, officers, employees and agents to the full extent
permitted by Delaware General Corporation Law, including in circumstances in
which indemnification is otherwise discretionary under Delaware law. In
addition, the Registrant has entered into separate indemnification agreements
with its directors, officers and certain employees which require the Registrant,
among other things, to indemnify them against certain liabilities which may
arise by reason of their status or service (other than liabilities arising from
willful misconduct of a culpable nature) and to maintain directors' and
officers' liability insurance, if available on reasonable terms. The Registrant
has directors' and officers' liability insurance with up to $100 million
coverage per year. These indemnification provisions and the indemnification
agreement between the Registrant and its officers and directors may be
sufficiently broad to permit indemnification of the Registrant's officers and
directors for liabilities (including reimbursement of expenses incurred) arising
under the Securities Act.

                               *         *         *

               Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers, and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.

ITEM 7.        EXEMPTION FROM REGISTRATION CLAIMED.

               Not applicable.

ITEM 8.        EXHIBITS.

                         
               Exhibit
               Number        Description
               ------        ------------



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               4.1           Form of Common Stock Certificate (filed as Exhibit
                             4.1 to the Company's Registration Statement on Form
                             S-1, Registration No.333-17729 and incorporated
                             herein by reference).

               4.2           Rights Agreement dated December 29, 1997 (filed as Exhibit 4.2 to the
                             Registrant's Form 8-K dated December 29, 1997 and incorporated herein by
                             reference).

               5.1           Opinion of Hogan & Hartson L.L.P. regarding the legality of the
                             shares being registered (previously filed).

               23.1          Consent of Hogan & Hartson L.L.P. (included in Exhibit 5.1).

               23.2          Consent of PricewaterhouseCoopers LLP (filed herewith).

               23.3          Consent of Deloitte & Touche LLP (filed herewith).

               24.1          Power of Attorney (previously filed).


ITEM 9.        UNDERTAKINGS.

               (a)    The undersigned Registrant hereby undertakes:

                      (1)    To file, during any period in which offers or sales
                      are being made, a post-effective amendment to this
                      registration statement:

                             (i) To include any prospectus required by
                      Section 10(a)(3) of the Securities Act of 1933;

                             (ii) To reflect in the prospectus any facts or
                      events arising after the effective date of the
                      registration statement (or the most recent post-effective
                      amendment thereof) which, individually or in the
                      aggregate, represent a fundamental change in the
                      information set forth in the registration statement.
                      Notwithstanding the foregoing, any increase or decrease in
                      volume of securities offered (if the total dollar value of
                      securities offered would not exceed that which was
                      registered) and any deviation from the low or high end of
                      the estimated maximum offering range may be reflected in
                      the form of prospectus filed with the Commission pursuant
                      to Rule 424(b) if, in the aggregate, the changes in volume
                      and price represent no more than a 20 percent change in
                      the maximum aggregate offering price set forth in the
                      "Calculation of Registration Fee" table in the effective
                      registration statement;

                             (iii) To include any material information with
                      respect to the plan of distribution not previously
                      disclosed in the registration statement or any material
                      change to such information in the registration statement.

                             Provided, however, that paragraphs (a)(1)(i) and
                      (a)(1)(ii) do not apply if the registration statement is
                      on Form S-3, Form S-8 or Form F-3, and the information
                      required to be included in a post-effective amendment by
                      those paragraphs is contained in periodic reports filed
                      with or furnished to the Commission by the Registrant
                      pursuant to Section 13 or Section 15(d) of the



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                      Securities Exchange Act that are incorporated by reference
                      in the registration statement.

                      (2)    That, for the purpose of determining any
                      liability under the Securities Act of 1933, each such
                      post-effective amendment shall be deemed to be a new
                      registration statement relating to the securities offered
                      therein, and the offering of such securities at that time
                      shall be deemed to be the initial bona fide offering
                      thereof.

                      (3)    To remove from registration by means of a
                      post-effective amendment any of the securities being
                      registered which remain unsold at the termination of the
                      offering.

               (b)    The undersigned registrant hereby undertakes that, for
purposes of determining any liability under the Securities Act of 1933, each
filing of the Registrant's annual report pursuant to Section 13(a) or Section
15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing
of an employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

               (c)    The undertaking concerning indemnification is set forth
under the response to Item 6.


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                                   SIGNATURES

        Pursuant to the requirements of the Securities Act, CIENA has duly
caused this Registration Statement to be signed on its behalf by the
undersigned, thereunto duly authorized, in the City of Linthicum, Maryland, on
this 10th day of April, 2001.

                                             CIENA CORPORATION


                                             By:  /s/ Michael O. McCarthy, III
                                                  ------------------------------
                                                  Michael O. McCarthy, III



        Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed by the following persons in the
capacities and on the dates indicated.


                                                   

Date: April 10, 2001                                    /s/ Patrick H. Nettles, Ph.D.*
                                                        ----------------------------------------
                                                        Patrick H. Nettles, Ph.D.
                                                        Chief Executive Officer, Chairman of the
                                                        Board of Directors
                                                        Principal Executive Officer


Date: April 10, 2001                                    /s/ Gary B. Smith*
                                                        ----------------------------------------
                                                        Gary B. Smith
                                                        President, Chief Operating Officer
                                                        and Director


Date: April 10, 2001                                    /s/ Joseph R. Chinnici*
                                                        ----------------------------------------
                                                        Joseph R. Chinnici
                                                        Sr. Vice President, Finance and Chief
                                                        Financial Officer
                                                        Principal Financial Officer


Date: April 10, 2001                                    /s/ Andrew C. Petrik*
                                                        ----------------------------------------
                                                        Andrew C. Petrik
                                                        Vice President, Controller and Treasurer
                                                        Principal Accounting Officer


Date: April 10, 2001                                    /s/ Stephen P. Bradley*
                                                        ----------------------------------------
                                                        Stephen P. Bradley
                                                        Director














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Date: April 10, 2001                                    /s/ Harvey B. Cash*
                                                        ----------------------------------------
                                                        Harvey B. Cash
                                                        Director


Date: April 10, 2001                                    /s/ John R. Dillon*
                                                        ----------------------------------------
                                                        John R. Dillon
                                                        Director


Date: April 10, 2001                                    /s/ Lawton W. Fitt*
                                                        ----------------------------------------
                                                        Lawton W. Fitt
                                                        Director


Date: April 10, 2001                                    /s/ Judith M. O'Brien*
                                                        ----------------------------------------
                                                        Judith M. O'Brien
                                                        Director


Date: April 10, 2001                                    /s/ Gerald H. Taylor*
                                                        ----------------------------------------
                                                        Gerald H. Taylor
                                                        Director


* pursuant to power of attorney


By: /s/ Michael O. McCarthy, III
   --------------------------
    Michael O. McCarthy, III
    Attorney-in-Fact


















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