A 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.

提出了一种波长锁定的光致热弹性光谱（WL-LITES）气体传感器系统，用于使用光纤耦合传感探头进行远距离原位甲烷（CH ₄）检测。波长锁定方案用于加快传感器响应速度，而无需扫描整个CH _4上的激光波长吸收线。采用具有宽光谱响应范围的小型压电石英音叉（QTF）来增强光热信号。基于实验和仿真对QTF的光激发参数进行了优化，以提高LITES技术的信噪比。使用Allan偏差分析来评估所提出的传感器系统的检测极限。WL-LITES气体传感器系统具有0.3 s的锁定积分时间和约100 m的光纤，显示出对CH _4的检测的最低检测限（MDL）约为体积（ppmv）的11 ppm ，并且MDL可以进一步降低到〜1 ppmv，平均时间为〜35 s。CH _4的实时原位监控 泄漏表明，所提出的传感器系统可以实现现场应用的快速响应（<12 s）。