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 CH₄ 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 CH₄ detection systems, our proposed method improves the detection limit further. In contrast to traditional fringe suppressing methods, our method has more advantages in CH₄ detection in open-path environments.

光学条纹易于在基于波长调制光谱（WMS）的气体检测中引起困难。在本文中，我们介绍了一种方便的条纹抑制方法。通过调制深度优化和两频调制技术，我们大大提高了CH _4的检测限。我们的实验采用 在开放路径环境中以λ = 1.654μm操作的分布式反馈激光器。传感器测量值的波动大大减少了约10–20倍。在50分钟的时间内，开放路径环境的最小检测极限提高到130 ppb m。与先前报道的其他近红外CH _4相比检测系统，我们提出的方法进一步提高了检测限。与传统的条纹抑制方法相比，我们的方法在开放路径环境中的CH ₄检测中具有更多优势。