Five-channel fiber-based laser Doppler vibrometer for underwater acoustic field measurement

In this paper, a 1550 nm five-channel all-fiber homodyne laser Doppler vibrometer with high sensitivity and good signal probing probability is presented. Under the anechoic tank, standing on an airborne platform above the water surface 3 m away, the calibration experiments of the designed system are conducted. The minimum detectable sound pressure level is up to 101.73 dB re 1 µPa at 10 kHz under the hydrostatic water surface condition, and the time distribution of the final outputs are consistent with that of the underwater sound transducer. For the hydrodynamic detection capability, with the help of a 1064 nm high-pulse-energy laser whose pulse energy is 6J, pulse duration is about 8 ns, and repetition rate is 1 Hz, the system performance is tested in Qiandao Lake. And the signal probing probability of the whole sensing system is up to 59.77%.