Polarization maintaining photonic crystal fibers

Photonic crystal fibers (PCFs) confine light by the regularly aligned cladding air-holes. PCFs can produce large birefringence of >10(-3) by asymmetrical structures. Since the polarization mode in the slow axis is hard to couple to the fast axis mode due to the large birefringence, such PCFs can be used as polarization maintaining fibers. To induce such anisotropy, some hole patterns can be considered. hi this paper, the structures of polarization maintaining PCFs, two defects type and enlarged type are described. In 100 m fiber, the extinction ratio better than -20 dB and -30 dB were obtained for former and latter type PCF, respectively. We have also examined the cross-talk degradation by the bending distortion. In the bending diameter of 10 mm, the cross-talk degradation was no larger than the measurement accuracy of 0.2 dB in such polarization maintaining photonic crystal fibers, but the 20 dB degradation was observed in the PANDA fiber, which was the conventional polarization maintaining fiber.