Fig. 1. Homodyne symmetric demodulation system based on 3×3 coupler

Fig. 2. Block diagram of NPS demodulation algorithm

Fig. 3. Real-time correction NPS fiber laser hydrophone signal demodulation system

Fig. 4. Block diagram of a fiber laser hydrophone signal demodulation method for real-time correction of NPS

Fig. 5. DC component and AC component of different periods. (a) DC component coefficient; (b) AC component coefficient

Fig. 6. Interference signals before and after normalization. (a) Before normalization; (b) after real-time normalization

Fig. 7. Demodulation effect before and after real-time correction. (a) Before correction; (b) after real-time correction

Fig. 8. Demodulation effect after loading 200 Hz and 4000 Hz sinusoidal signals. (a) Loading a sinusoidal signal of 200 Hz;(b) loading the sinusoidal signal at 4000 Hz

Fig. 9. Demodulation effect of continuous operation within 15 h. (a) Time domain spectrum; (b) spectrum in the frequency domain

Fig. 10. Experimental diagram of vibrating liquid column test method

Fig. 11. Real-time corrected interference signal in the experiment and experimental demodulation effect. (a) Real-time corrected interference signal in the experiment; (b) experimental demodulation effect