Hydromea's LUMA "Optical Modem" Offers Light-Based Wi-Fi-Like Connectivity Under the Waves

Hydromea, a startup spun out from the École polytechnique fédérale de Lausanne, has unveiled an "optical modem" designed to bring Wi-Fi-like high-speed communications capabilities to underwater sensors and drones operating at a distance of over 160 feet and depths of up to 20,000 feet.

Traditional radio systems don't work well for underwater, as the energy from the radio waves is absorbed by the water — and signals drop out after as little as three feet. Wired tethers work much more reliably, but limit where sensors and drones can be deployed or require that they're physically retrieved before data can be gathered. Acoustic communications, using vibrations within the water, are another option, but offer limited bandwidth and poor reliability.

Hydromea's alternative: An "optical modem" dubbed LUMA which can send and receive data using pulses of blue light. “We chose blue light because even though water is generally opaque for electromagnetic waves," Hydromea chief technology officer Felix Schill explains, "there is a small transparency band for blue and green light. That’s what lets our system send and receive data over long distances.

"Because light generally diffuses so rapidly underwater, finding a way to send communications over distances of 50 or 100 meters was difficult. It took us a long time to develop a receiver sensitive enough to capture tiny light pulses even from far away."

The finished LUMA system is fully sealed and can operate at depths of nearly 20,000 feet. Sensors can be placed by robotic drone, which can then pass over each sensor in turn in order to quickly retrieve data without physically interacting with them. The concept is already proven: LUMA has been deployed in the Pacific ocean for active research purposes, and the company is already discussing using the technology for pipeline work and offshore wind farm development.

More information is available on the EPFL website.