Spectral birefringence characterization of erbium-doped monomode optical fibers: relative values of the linear and the circular birefringence

Erbium-doped monomode optical fibers are widely used to build amplifiers, lasers, incoherent light sources and sensors. Since the performance of these devices can be modified by its spectral birefringence, it is important to characterize it. In the case of an elliptical retarder the determination of the sign of the linear birefringence and the relative value of the linear and circular distributed birefringence is not obvious. In this work we analyze the anisotropic response of erbium fibers assuming that they are uniform and behave as a distributed retarder with linear and circular birefringence. Taking advantage of the geometric properties of the Poincare sphere it is possible to separate the linear birefringence contribution from that of the circular birefringence and to determine their signs and relative values.