NEW YORK -- Metromedia Fiber Network, Inc. (MFN) (Nasdaq: MFNX - news), the leader in deployment of optical IP Internet infrastructure within key metropolitan areas domestically and internationally, announced today that it has received an extension of its commitment letter for the $50 million convertible debt investment from an investor. The commitment letter, which was scheduled to expire on September 21, 2001, has been extended until October 1, 2001.Metromedia Fiber Network Inc.(MFN)