Abstract
Abstract Optical fringes tend to cause difficulty in gas detection based on wavelength modulation spectroscopy (WMS). In this article, we introduce a convenient fringes suppression method. Through modulation depth optimization and two-frequency modulation technology, we substantially improve the CH 4 detection limit. Our experiment adopts a distributed feedback laser operated at λ = 1.654 μm in an open-path environment. The fluctuation of the sensor measurement is dramatically reduced by approximately 10–20 times. The minimum detection limit of the open-path environment improves to 130 ppb m for a 50-min period. Compared with other previously reported near-infrared CH 4 detection systems, our proposed method improves the detection limit further. In contrast to traditional fringe suppressing methods, our method has more advantages in CH 4 detection in open-path environments.
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