Proposal of high-birefringence twin-core hollow optical fiber

We propose a high-birefringence twin-core hollow optical fiber, which is composed of two rectangular Ge-doped cores, annular silica cladding, and a large central air hole. The rectangular cores are weakly coupled with the air hole and arranged in the same silica cladding. The mode birefringence in single-mode operation of 1.55 mu m reaches 2.48 x 10(-4), which is comparable with traditional panda polarization maintaining fiber. By introducing an extra stress zone, the mode birefringence can be improved further by two times. The high birefringence of the twin-core hollow fiber is induced by strong asymmetry of the waveguide structure. The characteristics of the guiding mode, birefringence, and evanescent field are analyzed numerically by full-vector finite-element method. The effect of geometric and material parameters is discussed. The proposed scheme of twin-core hollow fiber can overcome the polarization fading effect and signal cross talk occurring in traditional multicore fibers and is much desirable for improving the performance of in-fiber integrated interferometers and biochemical sensors. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)