Marine Electronics
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Traditionally, underwater wireless communications have been limited by speed. The water greatly reduces the maximum speed at which electronic signals can travel. However, new research at the Woods Hole Oceanographic Institution (WHOI), indicates that it is possible to transmit data without wires, underwater, at rates that are comparable to over-the-air wireless. Their new acoustic-optical underwater communication system, which will be deployed in July off the Juan de Fuca Ridge, will operate at data rates up to 20 megabits per second over a range of 100 meters.
At Juan de Fuca Ridge, researchers and technicians of WHOI will hop on board Alvin, a human occupied vehicle (HOV) for the send off of the wireless optical system and sub sea data concentrator. That system, once operational, will enable the researchers to gather real-time geophysical data from the wellheads that are located on the undersea ridge below.
Norman E. Farr, WHOI Senior Engineer, explained how the new technology would allow for economical high-speed underwater video transmission, “this combination of capabilities will make it possible to operate self-powered ROVs [remotely operate vehicles] from surface vessels without requiring a physical connection to the ROV.” Farr underscored that the optical/acoustic system, because it does not require cumbersome and bulky underwater cables to communicate, would allow for “much smaller, less-expensive ships and fewer personnel to perform undersea missions.
The new system, with inexpensive transmitters and receivers, has also been designed to work with much slower underwater acoustic systems and sensors. In this regard, the high-speed optical system and the low-speed acoustic system work together, such that the acoustic system will provide backup communications when the high-speed optical system is out of range.
Because the new optical system offers faster data rates, the new optical underwater communications system is now speed-compatible with and responsive to high-speed underwater data sensors. Effectively, scientists now have the ability to transmit ocean data as fast as the sensors can collect it. Because of this, scientists will now have not only the ability to monitor the vast amount of real-time data that occurs in the underwater world but also build new applications that can react to it.
Commenting was WHOI co-investigator Maurice Tivey “While acoustic communications has been the method of choice in the past it is limited by bandwidth and the bulkiness of transducers. Today, sensors sample at higher rates and can store lots of data and so we need to be able to download that data more efficiently. Optical communications allows us to transfer large data sets, like seismic data or tides or hydrothermal vent variations, in a time-efficient manner.”
Tivey also added that ‘underwater optical communications is akin to the cell phone revolution…wireless communications. 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.
When all is said and done, researchers envision a day when scientists will be able to control autonomous underwater vehicles (AUVs) easily from the office. In such a system, AUVs would collect underwater sonar images at close range and transmit that information over an optical modem to a mooring equipped with a satellite terminal. Scientists, back at the office, in response could order the AUV to perform specific tasks based on what comes into view on the PC screen.
Most important though, is the new real-time scientific universe that the technology will allow researchers to expand into. According to Farr, the system will “allow us to have vehicles [at specific undersea locations] waiting to respond to an event. It’s a game-changer.”
