A new methane sensor based on compound film-coated photonic crystal fiber and Sagnac interferometer with higher sensitivity

Abstract

A modified D-shaped photonic crystal fiber (PCF) based on Sagnac interferometer is proposed for methane concentration sensing. Two ultra-large air holes with methane-sensitive film are distributed horizontally in the PCF to shorten response time. Besides, a defect hole is introduced into the fiber core and theoretical analysis is carried out to enhance the sensing sensitivity. The dependence of gas sensitivity on the operable wavelength λ is obtained by analyzing the phase birefringence B(λ,C) and group birefringence Bg(λ,C). The average gas sensitivity is as high as 36.64 nm% in the sensing range of 0–3.5%. The modified D-Shaped and highly sensitive PCF sensor exhibits immunity to cross-sensitivity, and provides a new design idea for methane gas monitoring. Keywords: Photonic crystal fiber sensors, Methane sensing, Sagnac interferometer