中文摘要：

基于环形光路的Sagnac效应及腔袁荡测量技术原理，本文提出了一种新型的连续波腔衰荡微量气体浓度测量系统。系统中利用环形光路的Sagnac效应，将光纤环作为一个等效反射镜，与高反射率镜形成衰荡腔，实现衰荡腔的反射率可调，从而降低系统对入射光强度的要求，对信号处理提供了条件。在此基础上，文中对环形光路Sagnac效应和腔衰荡测量技术原理进行理论分析及推导，得到反射率与光纤环转速的关系、连续波腔衰荡微量气体浓度测量公式以及光纤环转速对微量气体浓度测量系统的影响，并通过仿真实验验证所设计系统的各项性能指标。

英文摘要：

A new measurement trace gas concentration system of Continuous Wave （CW） Cavity Ring-down Spectroscopy （CRDS） based on the effects of Sagnac and the measurement principle of cavity ring-down is proposed. The fiber loop based on the Sagnac effects served as a reflector and formed a resonator with a high-reflectivity reflector. It can achieve the reflectivity of the resonator tunable, therefore, the requirement of the intensity of incident light is decreased and condition of the signal processing is provided. On this basis, the theoretical analysis and derivation of fiber loop＇s Sagnac effect and the measurement principle of cavity ring-down are proposed. Meanwhile, we can obtain： the relationship between the reflectivity and fiber loop rotational speed, the formula of measurement of the trace gas concentration based on CWCRDS, and the influence of the fiber loop rotational speed on the measurement system of trace gas concentration. Finally, the various performance indexes of the system are proved via the simulation experiments.