Near-Infrared Dual-Gas Sensor System for Methane and Ethane Detection Using a Compact Multipass Cell

In this invited paper, a compact dense-pattern multipass cell-based near-infrared sensor system was demonstrated for detection of parts-per-billion in volume (ppbv)-level methane (CH 4 ) and ethane (C 2 H 6 ). The dimension size of the fabricated gas cell is 18.5 × 8 × 9 cm 3 with an absorption path length of 9.39 m. CH 4 measurement was realized within a spectral range of 6,046–6,048 cm −1 and an absorption line of 6,046.95 cm −1 . The spectral range for C 2 H 6 detection is 5,951–5,953 cm −1 with an absorption line of 5,951.73 cm −1 . Allan deviation analysis was used for evaluating the dual-gas sensing performance, and a detection limit of 78 ppbv for CH 4 and 190 ppbv for C 2 H 6 were achieved, respectively, with an averaging time of 0.8 s. Furthermore, CH 4 measurement in the indoor and outdoor atmosphere was both performed to verify the field sensing capability of the sensor system. Compared with two separate sensor systems for CH 4 /C 2 H 6 sensing, the proposed dual-gas sensor system using two near-infrared lasers and one multipass cell has the advantages of low-cost, compact-size without decreasing the selectivity and sensitivity.