US Patent 7133621 Optical communication with phase encoding and phase shifting

A communication system comprises a phase encoder, a phase shifter, and a modulator. The phase encoder receives user data and phase encodes the user data to form an encoded signal representing the user data. The phase shifter shifts a phase of the encoded signal to generate a phase shifted signal. The modulator receives a first optical signal and modulates the first optical signal with the encoded signal and the phase shifted signal to form an optical single sideband signal representing the user data. The modulator then transmits the optical single sideband signal representing the user data.