Fig. 1. Schematic diagram of interference based on Fabry-Perot sensor

Fig. 2. Orthogonal working point and linear interval^[24]

Fig. 3. Static working point stabilization system^[1]

Fig. 4. Schematic diagram of EFPI sensor system based on PGC demodulation principle

Fig. 5. Schematic diagram of PMDI-PGC demodulation system^[26]

Fig. 6. Schematic diagram of PGC-AD-DSM demodulation algorithm^[27]

Fig. 7. Schematic diagram of symmetrical demodulation method based on 3×3 coupler^[1]

Fig. 8. Experimental setup for interrogating an EFPI by using a three-wavelength method^[29]

Fig. 9. Dual-wavelength passive quadrature demodulation system^[30]

Fig. 10. Schematic diagram of dual-wavelength orthogonal demodulation algorithm

Fig. 11. Schematic diagram of dual-wavelength quadrature phase compensation demodulation algorithm

Fig. 12. Schematic diagram of dual-wavelength direct current compensation laser interference demodulation algorithm

Fig. 13. Experimental results of the EFPI with a cavity length of 129.946 μm at 1 kHz^［34］

Fig. 14. Schematic diagram of three-wavelength passive demodulation laser interference system^[35]

Fig. 15. Schematic diagram of three-wavelength passive demodulation laser interference algorithm

Fig. 16. Schematic diagram of experimental results of three-wavelength passive demodulation laser interference^［35］

Fig. 17. Schematic diagram of phase shift demodulation algorithm

Fig. 18. Schematic diagram of the experimental results of phase-shift demodulation^［37］

Fig. 19. Schematic diagram of three-wavelength symmetric demodulation algorithm

Fig. 20. Demodulation results. (a) Output signal when the cavity length is changed from 301.252 μm to 264.427 μm; (b)‒(d) enlarged images of areas indicated by the solid boxes in Fig. 20(a)^［38］