Radio waves travel poorly through water, making it very difficult for divers or submarines to wirelessly transmit information to the surface.
Scientists are trying to change this, however, by developing Aqua-Fi, an underwater version of Wi-Fi.
Two years ago, in 2018, researchers from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia used laser to transmit HD video through the water. Their new experimental system, known as Aqua-Fi, is based on that technology.
Wireless and underwater
Let's imagine a usage scenario of Aqua-Fi. A user (for example a diver) sends data (measurements, photos or videos) using one smartphone placed in a watertight container.
This data is initially transmitted in the form of radio waves, going within a few meters of a small device mounted on the diver's air tanks.
A microcomputer in that device then converts the data into a series of ultra rapid light pulses. Each pulse represents a 1 or a 0 in binary code.
Laser or LED?
These impulses are then sent to the surface, using an integrated 520 nanometer laser or a series of green LEDs. LEDs can send data at relatively short distances using little energy, while the laser can send it further but consumes more energy.
Upon reaching the surface, the light pulses are received by a photodetector placed under the keel of a ship, finally converted back into the original photos or videos from a connected computer. From there, the files can be uploaded to the Internet via satellite.
Sounds very complicated, right? In reality, the operation takes place very quickly.
Until now, the Aqua-Fi system has been used to upload and download multimedia files between two computers located a few meters apart in still water. Before it can enter real-world use it will need to be adapted to address challenges such as the light-scattering effect of rapidly moving water. To do this, a spherical receiver capable of detecting light pulses from all directions may be useful.
"We have created a relatively inexpensive and flexible way to connect underwater environments to the Internet," he says Basem Shihada, researcher at the head of the project.
"Hopefully one day Aqua-Fi will be as widely used underwater as Wi-Fi is on the surface."
The research is described in an article published in IEEE Communications Magazine, and could greatly improve rescue operations or oceanographic missions and in general all underwater activities.
