Abstract: A method of and apparatus for reducing unwanted mixing products on multiplexed optical communications lines, based upon the dispersion characteristics of the particular optical transmission line, in which a plurality of optical carriers are transmitted at substantially equally spaced apart frequencies over an optical fiber. When an unwanted mixing product is detected, a set of carriers that can be involved in producing the unwanted mixing product is determined. A carrier of the set is selected based upon the dispersion characteristics of fiber, and the frequency of the selected is shifted to eliminate the unwanted mixing product.

Abstract: A method of and system for detecting and reporting faults in an all-optical communications system. The system monitors each of the optical fibers and uses the optical supervisory channel system to detect and report faults. Whenever the system detects a fault in any of optical fibers, the system forms a message identifying the fault and transmits the message in the optical supervisory channel carried by at least one of the optical fibers.