Design and development of an LED-based optical communication system for autonomous underwater robots

Mobile networking and collaboration of underwater robots is of interest in many applications such as oceanography, environmental monitoring, and underwater surveillance. In this paper, an LED-based underwater optical communication system is designed and implemented for such applications. In contrast with laser-based communication systems, the characteristics of small size and low cost of the LED-based systems are very appealing, especially for small underwater robots. The presented system has a sound balance among desired characteristics of small size (in the order of centimeters), low energy consumption (500 mW on average), and median communication distance (20-30 m, in comparison with several meters available from most similar LED-based systems). The system design is described including the realization of the transmitter and the receiver, as well as the methods for achieving robustness to noise. System performance is experimentally tested in terms of signal strength and waveform shape versus communication distance and transmitting frequency. Experiments on data transmission is conducted to check the bit error rate under different baud rates. The experimental results show that the presented system has a good balance between communication performance and robustness.