Fig. 1. Schematic diagrams. (a) Schematic diagram of large-scale distributed fiber-optic hydrophone towing array; (b) schematic diagram of isolation cable; (c) schematic diagram of sensing array

Fig. 2. Distributed optical fiber hydrophone primitive. (a) Hydrophone primitive array physical images; (b) measured results of acoustic pressure sensitivity

Fig. 3. Schematic diagram of attitude perception system (illustration is physical photo of unit module developed)

Fig. 4. Fiber-optic hydrophone towing array preparation. (a) Physical image of fiber-optic hydrophone towing array; (b) Rayleigh scattering signal of optical fiber in 50 m sensing cable

Fig. 5. Demodulation system of distributed fiber-optic hydrophone towing array. (a) Physical image of uDAS system; (b) waterfall plot of demodulated acoustic signal response of uDAS system; (c) demodulated time-domain phase change of 100 Hz signal; (d) demodulated time-domain phase change of 400 Hz signal

Fig. 6. Lake trial test. (a) Track map of lake trial; (b) photo of towing process

Fig. 7. Towing attitude of hydrophone array. (a) Testing interface of attitude perception system; (b) hydrophone array depth data at 6 kn

Fig. 8. Hydrophone towing array noise analysis. (a) PSD of towing system at different sailing speed; (b) PSD for four frequencies varying with sailing speeds

Fig. 9. Results of signal frequency response. (a) Phase evolutions of 600 Hz signals from 12 channels; (b) PSD of 600 Hz signal; (c) PSD of 400 Hz and 500 Hz signals

Fig. 10. Signal beamforming. (a)(b) Spectrograms before and after beamforming; (c) 400 Hz power noise spectra

Fig. 11. Direction-of-arrival estimation. (a) Results of DOA; (b) relative bearing of underwater acoustic target detection