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Free space optical communication is the new way to communicate with the skies.

Lasers aren't just for destroying incoming missiles or driving your cat crazy. Laser beams can provide high-powered communications datalinks between ground stations and UAVs, aircraft, or satellites. For the last two years Airbus and the University of Oxford have collaborated on the Hyperion Project, an effort to develop an eye-safe laser data communications link between a ground station and a drone. Researchers have successfully flight-tested a proof-of-concept system with a range of about one kilometer. 

Why use lasers instead of ordinary radio? Well, the exponential rise of UAVs along with increasing numbers of satellites and aircraft is creating overwhelming demand for data communication and straining radio frequency (RF) bandwidth capacity. Higher and higher data transmission rates are eating additional bandwidth, and without alternatives, coping with the huge volume of data transmitted in the skies just won't be possible. 

Hyperion is one of many new projects seeking to use Free Space Optical (FSO) communications—systems that use directed visible or invisible light from a laser to establish a data link. FSO systems are potentially capable of data transfer rates up to a gigabyte per second and are less susceptible to jamming and interception than radio signals. NASA has used laser communications to talk to spacecraft, the technology would be key to establishing an interplanetary internet.

There are some big challenges to laser communication, however, such as developing links that have useful range and can deal with variable weather and atmospheric conditions. You've got to keep the laser directed on target, too, since it relies on line of sight. The Airbus/Oxford team focused on a method to steer a laser beam using a hologram and establishing an eye-safe datalink using low power retro-reflective technology. 

The Hyperion optical system aims a laser with a wavelength of 1550 nanometres up from the ground towards the target aircraft. The wavelength is important because 1550nm light does not focus on the human retina. That makes it eye-safe. The target aircraft is equipped with a Modulated Retro Reflector (MRR). The MRR captures the beam, modifies it with the data to be transmitted, and then sends it back to the ground where it can be decoded and "read".

Aiming a laser beam at an MRR carried by a drone or satellite requires precision pointing and tracking. Existing beam-steering systems use mirrors that are fragile and could be damaged during a UAV mission or a satellite launch. Hyperion improves on these by using a solid state device called a Spatial Light Modulator (SLM). The SLM allows precise horizontal and vertical steering of a laser beam as well as control of the beam divergence or focus. 

Such a laser system could allow drones engaged in disaster monitoring, surveying, search and rescue, or other missions to send detailed images back to the ground for analysis faster. Laser communication may also let airliners offload dense technical or performance data gathered by on-board sensors to ground crews during final approach to an airport. The advance info could speed up maintenance and cut turnaround times.

In 2015, the Hyperion scientists lab-tested an advanced MRR that achieved a data rate of 40 Mbps over a range of 5 meters. The team says that while it has demonstrated its tracking system at range of 1.2 km, that system could potentially operate with a range of 3 km (1.86 mi) or more depending on atmospheric conditions. The Hyperion system could be mature enough for commercial use by 2019. 

"Hyperion has the potential to enable extremely lightweight, low-power data terminals for UAVs," Oxford team leader Dominic O'Brien, says. That could make small UAVs or microsats laser data nodes in an increasingly networked sky.