Polarization state evolution in spun birefringent optical fibers

Abstract

The evolution of the polarization state (PS) of radiation propagating in spun or twisted birefringent optical fibers is considered for a wide range of fiber parameters, and presented in a descriptive way using the Poincaré sphere. The effects of the bandwidth and the polarization state of input radiation, of the external magnetic field, and of the fiber bending on the polarization state evolution have been described for the most practical cases. An explanation of how the helical structure of the built-in linear birefringence in spun fibers provides the existence of the helical elliptically-polarized eigenmodes has been given. In spun fibers with a relatively large spin rate, the PS evolution is shown to change its azimuthal direction.