A special periodic spectral fluctuation is observed during the study of a fibered high sensitivity optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS) for the measurement of trace gas. This spectral fluctuation is different from some phenomenon observed in former OF-CEAS which contain a resonant cavity with V-shaped configuration, such as the etalon effect and the spectral ripple effect. To reveal why this phenomenon happens and how it works, a series of hypothesis are proposed and tested, and the results show that the multi-beam interference of resonance light at the input mirror of the resonant cavity is the main reason for this phenomenon. Based on the multi-beam interference theory, a mathematical modeling of this phenomenon is built, and the theoretical analyses agree well with the experimental results. Some methods to eliminate this phenomenon are proposed and implemented, and the 1σ noise equivalent absorption coefficient of 7.6 × 10− 10 cm− 1 Hz-1/2 is attained with this robust and compact OF-CEAS system.

中文翻译：

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研究光纤反馈腔增强吸收光谱（OF-CEAS）中存在的周期性光谱波动

在纤维高灵敏度光反馈腔增强吸收光谱法（OF-CEAS）的研究中，观察到特殊的周期性光谱波动，用于测量痕量气体。这种频谱波动与以前的OF-CEAS中观察到的某些现象不同，前者在OF-CEAS中包含具有V形配置的谐振腔，例如标准具效应和频谱波纹效应。为了揭示这种现象发生的原因以及其工作原理，提出了一系列假设并进行了测试，结果表明，共振光在共振腔输入镜处的多光束干涉是造成这种现象的主要原因。基于多光束干涉理论，建立了该现象的数学模型，理论分析与实验结果吻合良好。