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Energy and data transmitted to underwater IoT devices on a beam of light

Image credit: Dreamstime

A system for powering and transmitting data to underwater IoT devices has been developed by researchers at the King Abdullah University of Science and Technology (KAUST).

Such devices placed in the ocean could help scientists more easily monitor remote underwater areas without worrying about volatile batteries losing their capacity or malfunctioning altogether.

It could ultimately lead to the deployment of self-powered underwater sensors for tracking climate change effects on coral reefs, detecting seismic activity and monitoring oil pipelines.

It could also enable the development of small autonomous robots for more accurate and extensive underwater search and rescue operations.

“Underwater acoustic and radio wave communications are already in use, but both have huge drawbacks,” said researcher and master’s student Jose Filho.

underwater iot device

Image credit: KAUST

“Acoustic communication can be used over large distances but lacks stealth (making it detectable by a third party) and can only access a small bandwidth.

“Furthermore, radio waves lose their energy in seawater, which limits their use in shallow depths. They also require bulky equipment and lots of energy to run.”

In its initial attempts the team was able to charge and transmit instructions across a 1.5m-long water tank to a solar panel on a submerged temperature sensor.

The sensor recorded temperature data and saved it on a memory card, later transmitting it to a receiver when information in the light beam instructed it to do so.

In another experiment, the battery of a camera submerged at the bottom of a tank supplied with Red Sea water was charged via its solar panel within an hour and a half by a partially submerged, externally powered laser source.

The fully charged camera was able to stream one-minute-long videos back to the laser transmitter.

“Underwater optical communication provides an enormous bandwidth and is useful for reliably transmitting information over several metres,” said co-first-author on the study Abderrahmen Trichili.

laser_beam_propagating_in_the_tank

Image credit: kaust

“KAUST has conducted some of the first tests of high-bit-rate underwater communication, setting records on the distance and capacity of underwater transmission in 2015.”

The use of simultaneous light wave information and power transfer configurations is known as SLIPT.

“SLIPT can help charge devices in inaccessible locations where continuous powering is costly or not possible,” Filho said.

Researcher Khaled Salama said: “These demonstrations were the first stand-alone devices to harvest energy, decode information and perform a particular function – in this case temperature sensing and video streaming.”

The team is now trying to find ways to overcome the effects of turbulence on underwater reception and looking into the use of ultraviolet light for transmissions that face underwater obstructions.

They are also developing smart underwater optical positioning algorithms that could help locate relay devices set up to extend the communication ranges of the devices.

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