Twin-half hollow elliptical core polarization-maintaining fiber for polarization state selective sensing

We propose and fabricate a twin-half hollow elliptical core polarization maintaining fiber. The shape of the core in the polarization maintaining fiber is designed to be elliptical for generating a geometry birefringence. In the cladding, two half-hollows are symmetrically distributed with respect to the elliptical core for producing a stress birefringence. Therefore, the birefringence in such a polarization maintaining fiber is the mixed effect of the geometry and stress birefringence. The birefringence generating mechanism is analyzed in detail and a theoretical formula depicting the birefringence is built up. The simulation results for the twin-half hollow elliptical core fiber at different structural parameters are obtained by using finite element method. Through adjusting the structural parameters of the fiber, the relationships between the birefringence and the core diameter as well as the width of the core bridge are discussed.