Hu, LienZheng, ChuantaoZhang, MinghuiZheng, KaiyuanZheng, JieSong, ZhanweiLi, XiuyingZhang, YuWang, YidingTittel, Frank K.2021-02-082021-02-082021Hu, Lien, Zheng, Chuantao, Zhang, Minghui, et al.. "Long-distance in-situ methane detection using near-infrared light-induced thermo-elastic spectroscopy." <i>Photoacoustics,</i> 21, (2021) Elsevier: https://doi.org/10.1016/j.pacs.2020.100230.https://hdl.handle.net/1911/109821A wavelength-locked light-induced thermo-elastic spectroscopy (WL-LITES) gas sensor system was proposed for long-distance in-situ methane (CH4) detection using a fiber-coupled sensing probe. The wavelength-locked scheme was used to speed the sensor response without scanning the laser wavelength across the CH4 absorption line. A small-size piezoelectric quartz tuning fork (QTF) with a wide spectral response range was adopted to enhance the photo-thermal signal. The optical excitation parameters of the QTF were optimized based on experiment and simulation for improving the signal-to-noise ratio of the LITES technique. An Allan deviation analysis was employed to evaluate the limit of detection of the proposed sensor system. With a 0.3 s lock-in integration time and a ∼ 100 m optical fiber, the WL-LITES gas sensor system demonstrates a minimum detection limit (MDL) of ∼ 11 ppm in volume (ppmv) for CH4 detection, and the MDL can be further reduced to ∼ 1 ppmv with an averaging time of ∼ 35 s. A real-time in-situ monitoring of CH4 leakage reveals that the proposed sensor system can realize a fast response (< 12 s) for field application.engThis is an open access article under the CC BY-NC-ND licenseJournal articleInfrared spectroscopyAbsorption spectroscopyLight-induced thermo-elastic spectroscopy (LITES)Methane detectionmethane-detectionhttps://doi.org/10.1016/j.pacs.2020.100230