Polarization-modulated coherent optical communication systems

Polarization modulated coherent optical communication systems are quite interesting for their simplicity, low phase noise induced penalty, and insensitivity to state of polarization fluctuations if a suitable tracking is adopted. In this paper different kinds of binary and multilevel polarization modulated systems are presented based on Stokes parameters detection. The structure of this class of systems is described and the polarization tracking algorithms are considered. Quantum limit performances are evaluated and the phase noise induced penalty is obtained both in the presence of a sample and hold decision device and in the case of postdetection filtering.