Shining Some Light on Free Space Optics
Free Space Optics: What is it?
Free Space Optical communication technology, Free Space Optics, or FSO for short, was first used by Alexander Graham Bell in 1880 in device he called the Photophone. This device turned sound waves into light, then transmitted these waves wirelessly through the air. Unfortunately Bell never got the photophone working over a distance of more than a few hundred meters. The Photophone is credited with being the mother of both fiber optics and Free Space Optics and was considered by Bell to be his most important invention (1).
Free Space Optics is the wireless transmission of data through free space using lasers. Free space includes air, outer space, vacuums etc. and employs the same concept as fiber optics, just without the cables. It is a much faster method of communication due to light being able to traverse air faster than it can fiber optic cables. (Light travels at 299,792,458 m/s through air and only 200,000,000 m/s through glass). Free Space Optics cause no interference with regular radio frequencies as the broadcasted transmission medium is infrared light. Free Space Optical systems are also much cheaper to install than fiber optics or microwave systems, and provide an extremely secure data connection. The laser beam being transmitted cannot be detected using an RF meter or a spectrum analyser. To intercept the signal you would need to be directly in the line of sight between the receiver and transmitter, which of course would cause the receiver to put out an alert due to it not receiving anything. Artolink has a commercially available FSO transmitter with a range of 2500m and a bandwidth capacity of 10 GB/s (2).
Free Space Optics could have been the front-runner for many communication systems, but it has lost out to fiber optics for a couple reasons. The number one reason is that FSO needs a direct line of sight between the receiver and transmitter in order for data communication. Mountains, trees and walls are obviously impenetrable, but fog causes a greater line of sight issue as it is unpredictable and opaque. FSO can penetrate through rain or snow with little issue, but dense fog can refract, reflect, scatter or complete block FSO laser beams. Even indoors without atmospheric interference the best commercial high bandwidth FSO systems only can travel a theoretical 2.5 kilometer maximum, though lower bandwidth increases range.
Free Space Optics in Space
Facebook is planning to use Free Space Optics on their internet drones (3).This
will come with many challenges, as they have to deal with problems concerning distance, atmospheric interference and accuracy (hitting an FSO receiver from a drone in the stratosphere is like hitting a dime from 16 kilometers away). Facebook has hired a team of experts to research and develop FSO technology, and if they succeed it will be a major improvement for the entire industry.
Free Space Optics have huge potential in space, as FSO beams can travel incredibly long distances with minimal interference. Free Space Optics are currently used for communications between spacecrafts. In January 2013, NASA used FSO lasers to send an image of the Mona Lisa to the Lunar Reconnaissance Orbiter roughly 386 000 km away. With technological advancements, free space optics could even bridge interplanetary distances. Though the technology has a long way to go before widespread adaptation, current developments and applications are certainly inspiring. The future looks brighter already!