Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to wirelessly transmit data for telecommunications or computer networking. “Free space” means air, outer space, vacuum, or something similar. This contrasts with using solids such as optical fiber cable. The technology is useful where the physical connections are impractical due to high costs or other considerations.
Free space optical communication on satellites
Optical communications are increasingly finding application in a variety of space missions, not only in experiments and/or demonstrations, but also for multi-year commercial purposes. This is the case for the optical inter-satellite links of the European data relay system (EDRS) involving two geostationary satellites flying and counting tens of thousands of optical links. The European Space Agency is also preparing an innovative project called High Throughput Optical Network (HydRON) to integrate an all-optical space transport network into the terrestrial fiber-based network. Reacting to this reality, the Consultative Committee for Space Data Systems (CCSDS) has been defining new specifications for different optical link scenarios through its optical working group (OPT). The first recommended standard in this area deals with high photon efficiency links, such as the ones encountered in deep space missions. The next target for the CCSDS OPT standardization effort is the design of a waveform for optical low Earth orbit direct-to-Earth links.