High birefringence in elliptical hollow optical fiber

We propose a novel design of highly birefringent optical fiber composed of a central elliptical air hole, a circumferential elliptical ring core, and a circular cladding. The proposed waveguide structure is predicted to produce a linear birefringence higher by an order of magnitude than the solid elliptical core fiber. The large index contrast between the central air and germanosilica elliptical ring core is mainly attributed to the high birefringence and its characteristics are theoretically analyzed in terms of its waveguide parameters.