An analysis of high birefringence fibers

A fiber is birefringent if it has a non-circular core and/or cladding, or is subjected to anisotropic stress. As a result of anisotropic stress, the fibers become biaxial. In this work, a theoretical study on the fields and dispersion of polarization modes in biaxial fibers is presented. The analysis is based on a perturbation method. In particular, the inclusion or exclusion of a term is determined by the differential equations, the boundary conditions and the symmetry of the problem, and does not rely on the prior knowledge of the fields in the fibers. The dependence of the fiber birefringence on the index difference and index anisotropy are determined. With the fields known, the excitation of high birefringent fibers can be analyzed. Methods for studying these excitation problems are indicated and some of the results are presented.