中文摘要：

根据可调谐二极管激光吸收光谱及谐波探测的原理，建立以分布反馈式半导体激光器为可调谐光源，利用多次反射池进行点式采样的实验装置。基于甲烷分子1653．7nm附近的吸收线，实验研究二次谐波信号对甲烷浓度的响应线性，并实现空气中甲烷本底含量的测量。研究结果表明可调谐二极管激光气体检测技术可为城市燃气管道泄漏探测提供了一种灵敏度高、抗干扰能力强的有效手段。

英文摘要：

The principle of tunable diode laser absorption spectroscopy and harmonic detection technique was introduced. An experimental device was developed by point sampling through small multi-reflection gas cell. A specific line near 1 653. 7 nm was targeted for methane measurement using a distributed feedback diode laser as tunable light source. The linearity between the intensity of second harmonic signal and the concentration of methane was determined. The background content of methane in air was measured. The results show that gas sensors using tunable diode lasers provide a high sensitivity and high selectivity method for city gas pipeline leak detection.