Two-pass gas signal detection system based on fiber loop ring-down cavity

To solve the problem of poor expansion of the traditional respiratory detection system, a detection system suitable for two-pass gas detection is proposed in this paper. A gas chamber is inserted into a fiber loop ring-down cavity. The key structural parameters, such as cavity length, optical attenuation factor, insertion loss, coupling rate, etc. Are studied. When testing two-pass gas signals simultaneously, the obtained theoretical time interval is 0.935 s. The proposed system can be potentially expanded to more signals.