Abstract: An optical communications system includes a receiver subsystem with at least two heterodyne receivers. The receiver subsystem receives a composite optical signal having two or more subbands of information and corresponding tones. An optical splitter splits the composite optical signal into optical signals. Each optical signal includes a subband(s) and corresponding tone. Each heterodyne receiver receives an optical signal. The receiver includes a heterodyne detector coupled to a signal extractor. The heterodyne detector mixes the optical signal with an optical local oscillator to produce an electrical signal which includes a frequency down-shifted version of the subband and the tone of the optical signal. The signal extractor mixes the frequency down-shifted subband with the frequency down-shifted tone to produce a frequency component containing the information.

Abstract: A transmitter subsystem generates an optical signal which contains multiple subbands of information. The subbands have different polarization. For example, in one approach, two or more optical transmitters generate optical signals which have different polarization. An optical combiner optically combines the optical signals into a composite optical signal for transmission across an optical fiber. In another aspect, each optical transmitter generates an optical signal containing both a lower optical sideband and an upper optical sideband (i.e., a double sideband optical signal). An optical filter selects the upper optical sideband of one optical signal and the lower optical sideband of another optical signal to produce a composite optical signal.