SECURED CONVERTIBLE PROMISSORY NOTE

Exhibit 10.2

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR THE SECURITIES LAWS OF ANY STATE, AND HAVE BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO, OR IN CONNECTION WITH, THE SALE OR DISTRIBUTION THEREOF. NO SUCH SALE OR DISTRIBUTION MAY BE EFFECTED WITHOUT AN EFFECTIVE REGISTRATION STATEMENT RELATED THERETO OR AN OPINION OF COUNSEL IN A FORM SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR THE APPLICABLE SECURITIES LAWS OF ANY STATE.

SECURED CONVERTIBLE PROMISSORY NOTE

(Restated Note)

For value received, Digital Lightwave, Inc., a Delaware corporation (the “ Company ”), promises to pay to Optel Capital, LLC, a Delaware limited liability company (the “ Holder ”), or its registered assigns, the principal sum of Thirty-Five Million, Six Hundred Fifty-Four Thousand, One Hundred Sixty Dollars ($35,654,160.00) with interest on the outstanding principal amount at a rate equal to the London Interbank Offered Rate (as defined below) plus 100 basis points. As used herein, the term “London Interbank Offered Rate” means the fluctuating rate of interest equal to the rate per annum equal to the British Bankers Association LIBOR rate (“ BBA LIBOR ”), as published by Reuters (or such other commercially available source providing quotations of BBA LIBOR as selected by the Holder from time to time) as determined for each business day at approximately 11:00 a.m. London time two (2) business days prior to the date in question, for dollar deposits (for delivery on the first day of such interest period) with a three month term. If such rate is not available at such time for any reason, then the rate for that interest period will be determined by such alternate method as reasonably selected by the Holder. The interest rate shall be computed on the basis of the actual number of days elapsed and a year of 360 days. This Note is issued pursuant to the Credit and Restructuring Agreement, dated as of April 4, 2008 (as amended, restated or otherwise modified from time to time, the “ Credit and Restructuring Agreement ”), by and between the Company and the Holder. Terms not otherwise defined herein shall have the meaning given to them in the Credit and Restructuring Agreement. This Note is subject to the following terms and conditions.

1. Maturity .

(a) Unless converted as provided in Section 2, (i) the entire unpaid outstanding principal amount shall be due and payable upon demand by the Holder at any time the earlier to occur of (I) March 31, 2010 and (II) the date on which written demand is made by the Holder in accordance with Section 2.3(c) of the Credit and Restructuring

Agreement (the “ Maturity Date ”) and (ii) the accrued and unpaid interest shall be due and payable in quarterly installments on the last business day of each of the Company’s fiscal quarters with the first interest installment payment due and payable on June 30, 2008.

(b) Notwithstanding the foregoing, the entire unpaid balance of principal and interest (the “ Aggregate Debt ”) shall become immediately due and payable upon demand by the Holder at any time on or following the occurrence of an Event of Default (as defined in the Security Agreement (as defined below)).

2. Conversion .

(a) Conversion into Common Stock; Conversion Price . The Aggregate Debt, or any portion thereof, shall be convertible at the option of the Holder into shares of Common Stock of the Company (“ Conversion Stock ”), at any time, and from time to time, following the Stockholder Meeting, at a conversion price per share (the “ Conversion Price ”) equal to the greater of (a) $0.01 or (b) 100% of the average of the daily volume-weighted average price of Common Stock quoted or traded on the over-the-counter market as reported by Pink Sheets LLC (the “ Pink Sheets ”) (or, if the Common Stock is not quoted or traded on the Pink Sheets at the time of conversion, such other primary market on which the Common Stock is quoted or traded) during the period of five consecutive trading days ending on the date immediately prior to the date of the conversion of this Note, from time to time.

(b) Disinterested Stockholder Approval . Notwithstanding anything contained in this Note to the contrary, it shall be a condition precedent to this Note becoming convertible pursuant to Section 2(a) above, that the Proposals