Direct air–water communication by using an optical-acoustic method

The Air-Water Cross-Medium Communication (AWCMC) is significant for ocean exploration. This work presents an approach to direct AWCMC based on the optoacoustic conversion technique, which utilizes a pulsed laser and a distributed feedback fiber laser (DFB-FL) hydrophone. On-off keying (OOK) is used to modulate the pulsed laser, and ASCII is selected as the signal coding format. The light signal after modulation is transmitted to the air–water interface, where it is converted into underwater sound signals by the optoacoustic effect. Next, the underwater acoustic signal containing the encoded information is detected and demodulated by the DFB-FL hydrophone, which proves the feasibility of the proposed method used for the AWCMC. The experimental results indicate that the ASCII-encoded OOK signals with varying repetition frequencies can be generated by modulating the laser. Then, the performance of laser-generated sound (LGS) communication is evaluated by measuring the data rate and bit error rate (BER) with the repetition frequency in the range of 1–500 Hz. It is found that both the data rate and BER exhibit a positive correlation with the repetition frequency of the pulsed laser. Therefore, when optoacoustic technology is applied to the AWCMC, optimization design is required for the indicators of data rate and BER.