Abstract: Transmission capacity of an optical fiber is increased by transmitting two optical signals of orthogonal polarizations through the fiber and distinguishing the signals from one another at the receiver by appropriately weighting polarization components representative of the transmitted signals. The weighted polarization components are summed to provide two output electrical signals that are proportional in magnitude to the two transmitted optical signals. Appropriate weighting of the signals eliminates cross-channel interference and maximizes the signal to noise ratio. Signals of arbitrary received polarizations are detected and separated from one another.

Abstract: Higher information rates are achieved in lightwave communication systems by using optical signals of different polarizations to represent data as ternary digits. Each ternary digit assumes a value, for example, of either zero, logic 1 (e.g., an amplitude of one unit) on a first polarization, or logic 1 on a second polarization. The ternary digits are transmitted to a receiver through a single optical fiber by modulating the optical signals in time with one of these two polarizations or zero. The receiver determines the value of each ternary digit by determining that the received optical signal has a value of either zero or logic one on a particular one of the two polarizations.

Abstract: Signal distortion in fiber optic systems is compensated for by forming decisions as to the transmitted information as a joint function of the received signal and of a feedback signal. The latter, in turn, is a function of decisions made for at least one signal transmitted over the fiber. The feedback signal determines the value of a threshold to which the received signal is compared in order to generate the decisions.