Fig. 1. Simulaed curves. (a) Response between amplitude and frequency; (b) relation between SNR and frequency

Fig. 2. Structure of photoacoustic probe. (a) Schematic of oil-gas separation and integrated sensor probe; (b) structure of oil-gas separation membrane

Fig. 3. Simulation of gas permeation through FEP membrane

Fig. 4. Absorption coefficients of C₂H₂ and interfering gases in the near-infrared region

Fig. 5. Diagram of detection system with gas dissolved in oil based on laser photoacoustic spectroscopy

Fig. 6. Photoacoustic signal voltage under different modulation currents

Fig. 7. Photoacoustic signal voltage versus oil-gas separation time

Fig. 8. Signals of C₂H₂ under different volume fractions. (a) Second harmonic signal; (b) peak voltage of second harmonic photoacoustic signal

Fig. 9. Result of Allan deviation analysis. Inset is continuous measurement results of C₂H₂ gas dissolved in oil with volume fraction of 10^-6

Fig. 10. Measured volume fraction of C₂H₂ gas dissolved in oil