Polarization-switching techniques for coherent optical communications

Several techniques which rely on forcing the polarization state of either the transmitted signal or local oscillator to vary with time in a nonadaptive manner so that polarization-sensitive performance is obtained are discussed. The proposed schemes adopt a novel approach which uses a birefringent medium (for example, high-birefringence single-mode fibers) to implement polarization switching. These techniques require only a single photodetector and give a fixed level of detection performance, with a power penalty of 3 dB relative to heterodyne detection with perfectly matched polarizations.>