Portable underwater audio communication system based on blue LEDs

With the expansion of human activities underwater, such as environmental monitoring, underwater exploration, and scientific data collection, there is an urgent need for a secure, reliable, and high-speed underwater wireless communication technology. Visible light communication technology, as a necessary path for future 6G high-speed wireless communication, has the advantages of high bandwidth, high confidentiality, lightweight equipment size, as well as meets the concept of carbon neutrality. With the rapid development of LED industry, LED-based visible light communication technology has also been widely used and developed, only that most of the researches are established under short distance and high-speed laboratory conditions. In view of the integration requirements of lighting and communication, as well as the serious attenuation of radio frequency communication in water that causes the limited transmission distance, and the low bandwidth of underwater acoustic communication, this paper demonstrates underwater audio transmission over 10 m distance, exploiting four blue (454 nm) LEDs at the transmitter and a photodiode at the receiver. The system uses STC15W4K60S4 microcontroller as the main control chip. The transmitter conducts low-pass filtering and signal amplification through MAX9813L and AD828, and drives LEDs to realize the conversion and transmission of electro-optic signals. The receiver uses photodiode to convert the received optical signal into an electrical signal, and generates the output signal of the audio playback device through transimpedance amplification and filter circuits. Underwater test results prove that the proposed communication system can achieve high audio transmission quality.