Polarization stabilization in optical communications systems

The control of the state of polarization (SOP) of light remains one of the open issues in optical communications. In particular, the achievement of a stabilization of the SOP can find many applications in advanced optical communication systems: from the mitigation of polarization-mode dispersion to the development of novel multilevel modulation formats. In this paper, theoretical and experimental aspects of polarization stabilization are dealt with, and a novel algorithm to overcome the issues related to the practical availability of finite-range birefringent components and to solve the requirement for endless stabilization is also presented. A complete analysis of the control algorithm, based on the Jones matrix formalism, is also presented. The practical implementation of the polarization stabilizer is discussed, and experimental demonstrations based on liquid crystal and magnetooptical retarders are shown.