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                                                                  EXHIBIT 10.13



                            SECOND AMENDMENT TO LEASE


1.       PARTIES

         1.1      THIS AGREEMENT made the _________day of ________, 1998 is by
                  and between MONMOUTH/ATLANTIC REALTY ASSOCIATES L.P.
                  (hereinafter "Lessor") whose address is c/o Mack-Cali Realty
                  Corporation, 11 Commerce Drive, Cranford, New Jersey 07016 and
                  DIGITAL LIGHTWAVE, INC. ("Lessee"), whose address is 601
                  Cleveland Street, 5th floor, Clearwater, Florida 34615

2.       STATEMENT OF FACTS

         2.1      Lessor and Lessee entered into a Lease dated September 26,
                  1997; (hereinafter "Lease") setting forth the terms of
                  occupancy by Lessee of 8,004 gross rentable square feet
                  (hereinafter "Premises") at 1340 Campus Parkway, Building B,
                  Wall, New Jersey (hereinafter "Building"); and

         2.2      The Term of the Lease is for five (5) years with the
                  Commencement Date of the initial Term being defined in the
                  Preamble to the Lease as being subject to change under
                  Articles 28 and 44 thereof; and

         2.3      It has been determined in accordance with the provisions of
                  Articles 28 and 44 of the Lease that December 1, 1997 is the
                  Commencement Date of the Term of the Lease; and

         2.4      Lessor and Lessee desire to amend the Termination Option
                  contained in the Lease.

3.       AGREEMENT

                  NOW, THEREFORE, in consideration of the Premises and the
         covenants hereinafter set forth, Lessor and Lessee agree as follows:

         3.1      The Commencement Date of the Term of the Lease is December 1,
                  1997 and the Expiration Date thereof is November 30, 2002 and
                  Articles 5 and 8 of the Preamble to the Lease shall be deemed
                  amended accordingly.

         3.2      Article 9 of the Preamble to the Lease is hereby confirmed as
                  being correct and reflects the above stated Commencement and
                  Expiration Dates.

         3.3      This Agreement is executed by the parties hereto for the
                  purpose of providing a record of the Commencement and
                  Expiration Dates of the Lease, to confirm the Term of the
                  Lease, and to confirm the Fixed Base Rent due for the Term.

         3.4      Lessor and Lessee agree to increase the consideration due
                  Lessor in the event that Lessee exercises its Termination
                  Option from Seventy-One Thousand One Hundred Eight and 00/100
                  Dollars ($71,108.00) to Eighty-Four Thousand Nine Hundred
                  Eighteen and 92/100 Dollars ($84,918.92) to reflect the
                  commission Lessor is paying Black and Company ("Broker") for
                  the cancelable portion of the Term of the Lease, and Article
                  54 of the Lease shall be deemed amended accordingly.

         3.5      Except as amended herein, the Lease covering the Premises
                  shall remain in full force and effect as if the same were set
                  forth in full herein and Lessor and Lessee hereby ratify and
                  confirm all the terms and conditions thereof.

         3.6      This agreement shall be binding upon and inure to the benefit
                  of the parties hereto and their respective legal
                  representatives, successors and permitted assigns.

         3.7      Each party agrees that it will not raise or assert as a
                  defense to any obligation under the Lease or this Amendment or
                  make any claim that the Lease or this Amendment is invalid or
                  unenforceable due to any failure of this document to comply
                  with ministerial requirements including, but not limited to,
                  requirements for corporate seals, attestations, witnesses,
                  notarizations, or other similar requirements, and each party
                  hereby waives the right to assert any such defense or make any
                  claim of invalidity or unenforceability due to any of the
                  foregoing.

                  IN WITNESS THEREOF, Lessor and Lessee have hereunto set their
         hands and seals the date and year first above written and acknowledge
         one to the other they possess the requisite authority to enter into
         this transaction and to sign this Agreement.

         MONMOUTH/ATLANTIC REALTY           DIGITAL LIGHTWAVE, INC.,
         ASSOCIATES L.P.,                   LESSEE
         LESSOR

         By:  Cali Sub VII, Inc.
              Managing General Partner

         By:                                   By:  
              -------------------------------       ---------------------------
              James G. Nugent                       Name:
              Senior Vice President - Leasing       Title: