Wireless optical ethernet modem for underwater vehicles

In order to achieve high speed data transfer in underwater which is low optical transparency, we developed an underwater optical communication modem using high power laser diode to make a link to further vehicles. Because the beam from the modem is not a collimated but narrow enough to keep the light power, precise axis alignment of light isn't needed before the communication, keeping range long. These characteristics are necessary for using it on vehicles or drones. In addition, the communication protocol of the modem is based on Ethernet, therefore the modem can be connected to various instruments easily. The modem was tested in a water tank under 100lx ambient light. 12.5Mbps communication speed was achieved by the modem at 46m range, and stable link through rough water surface was established in the test. The ability enable direct communication between air and underwater drones.