Fig. 1. Interference spectra at different FP microcavity lengths

Fig. 2. Glass tube end surface covered with GO film

Fig. 3. Measuring principle of interference spectrum

Fig. 4. Interference spectra of optical fiber acoustic vibration sensor in different environments. (a) Air; (b) water

Fig. 5. Simulation result of interference spectra of FP cavity

Fig. 6. Test and experiment system of acoustic vibration signal

Fig. 7. Spectra diagram of single frequency acoustic vibration signal in air. (a) 500‒900 Hz; (b) 1‒10 kHz; (c) 11‒19 kHz

Fig. 8. Spectra diagram of single frequency acoustic vibration signal under water. (a) 1‒10 kHz; (b) 11‒20 kHz

Fig. 9. Results of dual-frequency acoustic vibration in different environments. (a) Air; (b) water

Fig. 10. Results of three-frequency acoustic vibration in different environments. (a) Air; (b) water