Class 1 Eye-Safe Formally Invisible Underwater Optical Wireless Communication System

When using underwater optical wireless communication in areas close to human habitats— such as shallow sea areas—specifications for highly-secure, large-capacity optical transceivers are required. Real-time transmission of 850 nm, direct-current optical orthogonal frequency division multiplexing signals for full-duplex underwater invisible light communication has been achieved. We experimentally confirmed that subcarrier adaptive modulation could transmit at maximum capacity depending on the transmission distance, while changing the transmission distance in shallow seawater channels. We confirmed that there was no disturbing influence due to sunlight by using a honeycomb structure for sunlight shielding. Moreover, we found that the effect of disruption caused by the sea surface vibrating due to the 3 m/s wind speed did not affect the signal quality. 4K video streaming is also done on a 1.2 m underwater channel transmission. To the best of our knowledge, this is the first report of full-duplex transmission of invisible-band underwater optical wireless communication for shallow waters.