A fiber-optic methane gas sensor system with improved accuracy using absorption-spectrum matched comb filter

A fiber-optic methane gas sensor system is proposed and demonstrated with accurate gas concentration measurement with a sensitivity of ~410ppm. We employ the polarization-maintaining photonic crystal fiber (PM-PCF) based Sagnac loop filter to slice the spectrum of broadband light source so as to precisely match multiple absorption lines of the methane gas. Meanwhile, a compact gas cell with multiple reflections is designed to enhance the interaction between methane gas and the light beam. The proposed gas sensor is verified as low cost, temperature-insensitive, and high sensitivity.