New optical system to revolutionize undersea communications - - India News Times

Scientists and engineers have devised an undersea optical communications system that-complemented by acoustics-enables a virtual revolution in high-speed undersea data collection and transmission. Woods Hole Oceanographic Institution (WHOI) scientists and engineers have devised the new system. Compared to communication in the air, communicating underwater is severely limited because water is essentially opaque to electromagnetic radiation except in the visible band. Even then, light penetrates only a few hundred meters in the clearest waters; less in sediment-laden or highly populated waters. Consequently, acoustic techniques were developed, and are now the predominant mode of underwater communications between ships and smaller, autonomous and robotic vehicles. However, acoustic systems-though capable of long-range communication-transmit data at limited speeds and delayed delivery rates due to the relatively slow speed of sound in water. Now, Farr and his WHOI team have developed an optical communication system that complements and integrates with existing acoustic systems to enable data rates of up to 10-to-20 megabits per second over a range of 100 meters using relatively low battery power with small, inexpensive transmitters and receivers. The advance will allow near-instant data transfer and real-time video from un-tethered ROVs and autonomous underwater vehicles (AUVs) outfitted with sensors, cameras and other data-collecting devices to surface ships or laboratories, which would require only a standard UNOLS cable dangling below the surface for the relaying of data. According to WHOI Senior Engineer Norman E. Farr, who led the research team, this would represent a significant advance in undersea investigations of anything from the acidity of water to identifying marine life to observing erupting vents and seafloor slides to measuring numerous ocean properties. In addition, the optical system would enable direct maneuvering of the vehicle by a human. The ability to transfer information and data underwater without wires or plugging cables in is a tremendous capability allowing vehicles or ships to communicate with sensors on the seafloor. "Optical communications allows us to transfer large data sets, like seismic data or tides or hydrothermal vent variations, in a time-efficient manner," said co-investigator Maurice Tivey of WHOI. When the vehicle goes out of optical range, it will still be within acoustic range, according to the researchers. "Because it enables communications without the heavy tether-handling equipment required for an ROV , the optical/acoustic system promises to require smaller, less-expensive ships and fewer personnel to perform undersea missions," Farr said.