Improving reliability of laser-generated sound across-media communication by FSK method

Laser-generated ultrasound (LGU) presents a viable solution to the challenge of direct air-sea cross-media communication. This paper describes a method to enhance the anti-interference capabilities of LGU communication technology by employing frequency shift keying (FSK). An LGU-air-water cross-medium communication (AWCMC) system was established using a pulsed laser and a distributed feedback fiber laser (DFB-FL) sensing system. The FSK-encoded information is modulated onto the pulsed laser via an external trigger, then converted into ultrasound signals at the air-water interface through the photoacoustic conversion effect. These signals are detected by the DFB-FL sensing system, and the information is subsequently decoded using the convolution method on a computer. Experimental results demonstrate that FSK modulation significantly improves the anti-interference performance of AWCMC at a 250 Hz repetition rate, achieving up to 16FSK modulation and a maximum communication rate of 53 bps. The preliminary findings suggest the potential application of this system based on pulsed laser and DFB-FL sensors in AWCMC.