Reflectometric measurements of PMD parameters in long single-mode fibers

Polarization-sensitive optical time domain reflectometry is an effective tool for the analysis of birefringence properties of long single-mode fibers. In this paper, we review its theory and the main experimental results. Until now, all the experimental results confirm that linear birefringence is a random process, very well described by the Wai-Menyuk model. Moreover, in some cases experimental evidences of circular birefringence, induced by constant twist-rate, were found.