A method for conveying information through an optical fiber link between a transmitter and a receiver of an optical communication system. The method includes generating, by the transmitter, a predetermined spectral change, and inserting the predetermined spectral change into an optical fiber link for transmission to the receiver. A detector associated with the receiver detects the predetermined spectral change in an optical signal received through the optical fiber link, and generates a detection signal in accordance with the detection result. The detector is independent of a digital signal processor of the receiver that is configured to recover data modulated on the optical signal received through the optical fiber link.