Fig. 1. Schematic diagram of optical cavity ring-down spectroscopy

Fig. 2. Schematic diagram of the measurement system

Fig. 3. Simulation of CO₂ absorption feature and interference absorption of H₂O vapor and CH₄

Fig. 4. Framework of the optical resonant cavity

Fig. 5. Error signal measurement values

Fig. 6. Allan analysis of variance and ring-down times

Fig. 7. Linear analysis of absorption coefficient and nominal values

Fig. 8. Results of system and picarro comparison test