Abstract
Wavelength modulation spectroscopy (WMS) with second harmonic detection is an extremely effective technique to detect gases in site applications. However, the significant levels of nonlinear effects in a system give rise to high background signals that either limit detection sensitivity or distort the harmonic signals. This paper outlines the theory of WMS-involved background signals and focuses on the elimination of undesirable effects in the background. A real-time, long-distance methane sensor using a tunable diode laser near 1653.7 nm is developed to continuously monitor methane by using a variable optical attenuator to suppress the background. Trace methane detection experiments verify that the minimum detection limit of the system can be increased by 47.5 times compared to the traditional WMS method.
© 2020 Optical Society of America
Full Article | PDF ArticleMore Like This
Hongze Lin, Fei Gao, Yujian Ding, Chunsheng Yan, and Sailing He
Appl. Opt. 55(28) 8030-8034 (2016)
Tie Zhang, LiHui Wang, Yan Huang, Haijie He, Sailing He, and GaoXuan Wang
Appl. Opt. 62(24) 6464-6471 (2023)
Haibin Cui, Fei Wang, Qunxing Huang, Jianhua Yan, and Kefa Cen
Appl. Opt. 59(30) 9491-9498 (2020)