Geometrical birefringence in a class of step-index fiber

Based on a scalar wave equation including the geometrical effect, an effective-index method is developed for the calculation of geometrical birefringence, i.e., the difference in phase velocity between the two fundamental polarization modes, in a weakly guiding step-index fiber, of which the core can be of rectangular, elliptical, rhomboid or any other shape belonging to the same class, with arbitrary aspect ratio. Numerical results show that the method is very efficient and accurate in obtaining the birefringence and can also provide very useful information on the birefringenee-induced dispersion in the fiber.