An optical communication system includes a transmitter for a generating a subcarrier multiplexed optical signal, a receiver and an optical fiber for coupling the optical signal from the transmitter to the receiver. At the transmitter, an optical carrier is modulated with a composite modulation signal...http://www.google.com/patents/US4989200?utm_source=gb-gplus-sharePatent US4989200 - Coherent subcarrier multiplexed optical communication system
