Bending Induced PMD in Spun Erbium Doped Fiber

With a growing number of systems running at 10 Gbit/s and large interest in 40 Gbit/s systems, there is increased focus on Polarization Mode Dispersion (PMD). Even though EDF amplifiers only consist of tens of meters of EDF, the PMD tolerance on the fiber is tight. But measuring the correct PMD in an EDF is not trivial [1]. Characterizing the intrinsic birefringence originating from geometric deformities in the fiber will not necessarily reveal the performance of the fiber in a coiled configuration, due to the interference between the externally induced birefringence from bending and the intrinsic birefringence, mitigated from spinning the fiber during draw [2], [3]. In this paper we demonstrate that coiling a fiber to diameters less than 10 cm can lead to significant bending induced PMD. Furthermore, we show that coiling high PMD spun fiber leads to highly unpredictable results