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LiFi enables underwater data transmission 6000 meters below sea level


Hydromea, a spin-off from the Swiss Federal Institute of Technology in Lausanne (EPFL), has developed a miniature optical modem that can operate up to 6,000 meters below the ocean surface. It is sensitive enough to collect data at very high speed from sources more than 50 meters away.

Radio waves can hardly work underwater because they are easily absorbed by water. Wireless internet connection underwater is therefore almost impossible. But it would be a different story if the connection was based on light.

Hydromea uses light to transmit data below the surface of the ocean or lake. They have developed an underwater modem called LUMA that communicates via a rapidly blinking blue light. The modem converts data into pulses of light that it sends out, or vice versa, converts the light pulses it receives into data, all in the blink of an eye. “Our optical modem gives you a fast wireless underwater connection,” says Alexander Bahr, COO of Hydromea.

(Photo: EPFL)

“We chose blue light because although the water is generally opaque to electromagnetic waves, there is a small band of transparency for blue and green light. This is what enables our system to send and receive data over long distances, ”explains Felix Schill, CTO of the company. While water easily absorbs most waves, and infrared in particular, only blue and green lights can pass through it. The red and yellow light waves of the sun are absorbed in just a few meters.

The hardest part of LUMA’s development was making sure it could send data over long enough distances and perform reliably in all kinds of conditions. “Because light usually diffuses so quickly underwater, it was difficult to find a way to send communications over distances of 50 or 100 meters,” says Schill. “It took us a long time to develop a receiver sensitive enough to capture tiny pulses of light, even from afar. “

(Photo: EPFL)

LUMA is designed to operate at depths of up to 6000 meters. It is a unit fully contained in a plastic casing, which is completely enclosed in clear plastic so that it does not collapse under extreme water pressures. The system has already been tested in the Pacific Ocean, 4,280 meters below sea level, by scientists at the Alfred Wegener Institute for Polar and Marine Research in Germany. It is the first research institute with which Bahr and Schill started to work. “We were then contacted by companies operating at sea who were interested in our technology for laying submarine pipelines or building foundations for offshore wind farms,” Bahr explains.


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