腔衰荡光谱技术一直是高灵敏度传感领域的关键技术之一，光纤腔衰荡传感方法能测量物理、化学和生物等多领域的关键参量，是腔衰荡光谱技术的重要发展趋势和当前研究热点。而光纤腔衰荡技术因空腔损耗大等原因，其灵敏度一直难以提高，尤其是气体测量的灵敏度远远不及传统腔衰荡光谱技术，迫切需要研发新的方法。光的干涉是灵敏度最高的技术之一，光纤频移干涉技术还具有许多独特优点，本项目据此提出将光纤频移干涉和腔衰荡两项高灵敏技术融合，使对腔衰荡信号的处理从时间域变到空间域，降低了系统对光源和信号采集等的过高要求，提高了系统稳定性。需要开展基于频移干涉的连续波空间域光纤腔衰荡传感理论和特性、光纤腔衰荡传感用低损耗关键器件（如传感器及其复用）的研究，并通过多参量传感实验进行验证，着重突破CO痕量气体检测应用的关键技术，对于探索实现一种具备监测多种跨学科参量的高灵敏光纤传感新技术，具有十分重要的科学意义和实用价值。

Cavity ring-down spectroscopy（CRDS） technique is one of the vital technology in the field of high sensitivity sensing. Fiber cavity ring-down sensing method can be applied to measure key parameters in the physical, chemical and biomedical field, which is an important trend of development of CRDS technique and is becoming the research focus nowadays. Due to the big loss of the cavity, the sensitivity of fiber cavity ring-down technology was difficultly impoved in the past several years, especially the sensitivity of gas measurement is far less than that by the traditional CRDS technique. Thus, there is an urgent need to develop new methods. Optical interference is one of the highest sensitive technology, and there are many unique advantages for the technique of fiber frequency-shifted interferometry(FSI). So the project proposes to combine fiber FSI and cavity ring-down(CRD), and to transform the signal processing of the CRD from time domain to spatial domain, which can reduce the performance requirements of the sensing system to light source and data acquisition, and can improve the stability of the system. The proposal needs to carry out the theory and characteristics of continuous-wave spatial-domain fiber cavity ring-down sensing, and to research the low-loss key components used by the fiber cavity ring-down sensing (such as various sensors and its multiplexing), to verify the novel method through many experiments of sensing multi-parameter. Besides, we will focuse on breakthroughs of key technology in the application of CO trace gas detection. There are very important scientific significance and practical values to explore a novel technology of optical fiber sensing with high sensitivity to monitor a variety of interdisciplinary parameters.