We report on the hard-target reflection spectroscopy of carbon monoxide (CO) gas based on the technique of infrared tunable diode laser absorption spectroscopy aiming at developing a low-cost yet sensitive sensor for the early detection of spontaneous coal combustion. A narrow-band distributed feedback laser emitting around 2333.7 nm is used to monitor CO gas molecules contained in a 5 cm gas cell. The light diffusely backscattered from the surface of a lump of coal placed at the end of a 50 cm light path is detected with a photodiode in the coaxial transmitter/receiver setup. From the variation of the detected signal profile with the CO partial pressure in the cell, the detection limit of the current system is estimated to be about 30 parts per million per meter (ppm·m), which meets the sensitivity required for monitoring the self-heating of coal in mines, silos, or stockpiles.

中文翻译：

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用于早期检测煤自燃的一氧化碳气体浓度的硬靶反射激光光谱

我们报告了基于红外可调谐二极管激光吸收光谱技术的一氧化碳（CO）气体的硬目标反射光谱，旨在开发一种低成本且灵敏的传感器，用于早期检测煤炭自燃。使用发射约 2333.7 nm 的窄带分布式反馈激光来监测 5 cm 气室中包含的 CO 气体分子。使用同轴发射器/接收器装置中的光电二极管检测从放置在 50 cm 光路末端的煤块表面漫反射的光。从检测到的信号曲线随细胞内CO分压的变化来看，当前系统的检测限估计约为百万分之30每米(ppm·m)，满足监测自体检测所需的灵敏度。 - 矿井、筒仓或库存中的煤炭加热。