Radio waves don’t travel well through water, which means that in order to send a robot down underwater and to communicate with it, in the past this would have involved using a tether in the form of a cable. However, the downsides are obvious, like not being able to go deep enough because the cable would have a fixed length.
However, Swiss startup Hydromea has created an underwater drone called the ExRay that actually uses light to communicate with the surface, thus eliminating the need for a tether. How it works is that the binary data is being sent through the water using rapid pulses of light between two optical modems – one on the drone and the other on the surface.
As the rate of transmission is at 10 megabits per second, it will allow for HD videos to be sent back to the surface with lag that’s imperceptible. However, as cool as this sounds, the company says that there are some limitations, such as how the ExRay has a communications range of 50m in clear water and complete darkness, which means that more polluted water or ambient light could decrease that range further.
However, the company is working on increasing that range to at least 100m. For now, the ExRay is being intended for use in enclosed spaces like inspection of a ship’s ballast tanks, so there isn’t really that much need for a long range at this point in time.