Temperature Insensitive All-Fiber Compact Polarization-Maintaining Photonic Crystal Fiber Based Interferometer and Its Applications in Fiber Sensors

A novel temperature insensitive all-fiber compact polarization-maintaining photonic crystal fiber (PMPCF) based interferometer was presented. The coupling between the PMPCF and single mode fiber (SMF) was investigated experimentally and analytically. With an all-fiber compact SMF-PMPCF-SMF structure, the cladding modes propagating in the PMPCF can be effectively excited by finely core-offsetting one splice between the PMPCF and SMF. With the increase of the core-offset, the interference depth of the interference pattern enlarges accordingly. Under a suitable core-offset, the PMPCF based interferometer with high interference depth can be obtained. Moreover, it is temperature insensitive due to its ultra-low thermal characteristics. We also demonstrated its applications in strain and refractive index measurement. The sensors have the advantages of small size, simple and compact all fiber structure, high sensitivity, and temperature insensitiveness.