Transverse-Stress Compensated Methane Sensor Based on Long-Period Grating in Photonic Crystal Fiber

A high-sensitive and transverse-stress compensated methane sensor based on a photonic crystal fiber long-period grating (PCF-LPG) is proposed. The outermost layer of the PCF consists of six large side-holes, five of which are coated with methane-sensitive compound film to achieve methane measurement. Such side-hole structure is helpful for gas sensitive reaction, but not conducive to avoiding external stress interference. Therefore, the last large hole is plated with silver layer to eliminate the cross-sensitivity effect through adding a Surface Plasmon Resonance (SPR) sensing channel with the consideration of photo-elastic effect and material deformation. Results show that the methane gas sensitivity can reach up to 6.39nm/% with the transverse-stress compensation. The sensor is very simple and effective, which provides a new method of gas measurement combined with different actual conditions.