(Free Space Optics) Transmitting optical signals through the air using infrared lasers. Also known as "wireless optics," FSO provides point-to-point and point-to-multipoint transmission at very high speeds without requiring a government license for use of the spectrum. FSO requires line of sight.

Because weather conditions such as fog can reflect light signals, redundant paths can be created by sending multiple signals to reflectors on different buildings. Transmitters with multiple beams are also used to provide greater reliability.

While FSO is being deployed for last mile connectivity, in time, it is expected to be used for short distances within high-speed buses in computers and switches, perhaps even within the chip itself.