Optical distribution of analog and digital signals using optical

Abstract

A novel optical system is taught including an optical source, an optical modulator having at least one optical input port for receiving the optical signal from the optical source, a modulation port for receiving the optical signal from the optical source, a modulation port for receiving a modulating signal, and complementary output port signals. The complementary modulated output signals are applied to one or more optical receivers at the other end of an optical transmission link. In one embodiment, the two complementary signals are provided to two separate optical receivers, thereby allowing distribution of optically modulated signals, for example, in a cable television or other type distribution system. In another embodiment, the two complementary modulated signals are applied to a single balanced receiver, thereby providing information content to the complementary receiver twice the power level available on either one channel alone. Furthermore, utilizing a balanced receiver, common mode error signals cancel, thereby increasing the signal to noise ratio of the system. In one embodiment of this invention, a single optical transmission channel is used, and the two optically modulated signals are separated in polarization so as to be capable of being separately detected on the receiving end of the link. In one embodiment feedback means is used to insure proper polarization states for the two complementary signals.