The story of optical satellite communications is a tale of the search for more bandwidth. Physics defines the terrain of the search — communicating across vast distances of space can only be accomplished using the electromagnetic spectrum, or EMS, where the higher the frequency (and the shorter the wavelength), the more data is encodable in the waveform. From S-band through C-band, to X-band and K-band, radio frequency, or RF, satellite communications have evolved from low-frequency dial-up speeds to today’s multi-gigabit per second very high throughput satellites using wavelengths under one centimeter.
But the highest frequencies of all in the electromagnetic spectrum are in the visible light end of the spectrum, up to 10,000 times higher than even the highest frequency Ka-band RF. The technology has existed to encode data in visible light since the development of fiber optic communications in the ‘70s and ‘80s. By that time, lasers were already a mature technology, used in consumer electronic devices like laserdisc or CD players.
The use of lasers to communicate data from satellites — sometimes called free-space optical communications, or FSOC, — has been a theoretical possibility for more than 40 years. The Japan Aerospace Exploration Agency demonstrated the technology in 1995, successfully achieving 1 megabit per second data download speeds from its engineering test satellite KIKU-6 to a ground station in Tokyo.
Today, a dozen or so companies, from startups to aerospace giants and major defense contractors are developing and selling free space optical technology, either to communicate with ground stations or between satellites in orbit or other spacecraft, with speeds up to 100 gigabits a second. Several test or demonstration projects are launching this year and if they are successful, the next two to four years could finally see the start of broad-scale deployment of FSOC technology in military and commercial constellations.