Fig. 1. Absorbance lines of H₂S， CH₄ and H₂O in infrared band

Fig. 2. Mid-infrared open-circuit H₂S and CH₄ multi-component gas concentration measurement experimental system based on 8.309 μm QCL quantum cascade laser

Fig. 3. Optimal analysis of modulation depth

Fig. 4. Comparison between the original 2f signal and the filtered 2f signal

Fig. 5. Comparison of 2f signals before and after water vapor filling

Fig. 6. Calibration and fitting of gas

Fig. 7. Long-term concentration monitoring of gas mixtures

Fig. 8. Allan deviation analysis for each gas

Fig. 9. Outfield sensing experiment diagram

Fig. 10. Comparison of 2f signals at different sensing distances

Fig. 11. Signal-to-noise ratio of 100 ×10^-6 m H₂S 2f signal

Fig. 12. System response time

Fig. 13. [in Chinese]