Using a connected device underwater is no easy task. Radio waves don’t work well – they are easily absorbed by water, meaning they can’t go much further than a meter. Many sensors only offer a wired connection, but they are impractical because you have to remove the devices from the water to recover their data. Acoustic communication is often used, but it is very slow and unreliable. These are significant obstacles to effective communications when it comes to underwater construction, inspection, monitoring and repair activities – such as in the offshore energy sector.
The engineers from EPFL spin-off Hydromea have come up with a solution: using light to transmit data below the ocean or lake surface. They have developed an underwater modem called LUMA that communicates through a rapidly blinking blue light. The modem converts data into light pulses that it sends out, or inversely, converts light pulses that it receives into data.
Instant data collection for limnologists
Fully contained in a plastic casing, LUMA is designed to work at depths of up to 6,000 meters. The system has already been tested in the Pacific Ocean, at 4,280 meters below sea level. Hydromea is also helping develop robotics and communications systems for LéXPLORE, a research platform located just off the shores of Lake Geneva, near Pully in the canton of Vaud.
There, limnologists are using LUMA to regularly check on the data collected underwater and make sure the measurement instruments are working properly, since the sensors need to remain underwater for months at a time. One modem is installed on the data logger which collects scientific data from the submerged sensors and the other modem is installed on a subsea robot that dives down to where the sensors are located and collects the sensors’ data instantly.