Remotely-operated vehicles (ROVs) underwater have a limiting factor that they need to be connected to a surface support ship physically by a long tether if the operators want to see what the ROVs’ cameras are seeing. That is about to change. Scientists are developing a two-way system that uses lasers to wirelessly transmit video through the water.
Ph.D. student Abdullah Al-Halafi and his supervisor Basem Shihada created the underwater wireless optical communication (UWOC) at King Abdullah University of Science and Technology (KAUST). It has only been tested in a lab setting for now and was able to successfully send and receive signals through a distance of 4.5 meters.
An underwater platform converts ultra HD digital video into a series of extremely rapid pulses, which are emitted by a 520-nanometer green laser diode. A downlink channel is formed which travels through the water and is picked up by a photodiode-equipped receiver, where it is converted back to the real-time video.
The receiver uses a 450-nm blue laser to form the uplink channel. This transmits the data back to the underwater platform. The data includes feedback on the signal quality of the received video. The underwater platform uses the feedback to change the power and modulation of the video signal.
The speed of transmission depends on the quality of the water but the quality is not compromised. “The end user will not experience any difference in video quality, as the system delivers video packets with the same definition, but at optimized power and transmission rates,” says Al-Halafi.
This system to transmit video underwater means that ROVs will no longer have to be physically connected to control ships on the surface in the future. A pretty cool development for the future of underwater exploration!