On the birefringence evaluation of single-mode fibers

Due to its low absorption, short lengths of single-mode fibers are modeled as homogeneous retarders and their birefringence is measured using polarimetric techniques. Usually this characterization is limited to the evaluation of intensity changes of the output polarized signal. These measurements provide information on the retardation rate, described in terms of the polarization beat length but do not provide information on the type of retarder (linear, circular or elliptical) and its polarization eigenmodes. Furthermore, most fibers present residual torsion, a contribution that breaks the periodic evolution of the polarization state associated to the polarization beat length. In this work we present and compare the techniques used to characterize the fiber birefringence emphasizing the changes introduced by the presence of residual torsion and show how to overcome this problem.