Free-space optical communication

An eight-beam free-space–optics laser link, rated for 1 Gbit/s. The receptor is the large lens in the middle, the transmitters the smaller ones. At the top right corner is a monocular for assisting the alignment of the two heads.

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 over long distances. "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.