Optical Wireless Communications (OWC)
Optical wireless communications (OWC) is an umbrella term describing any optical communication technology that does not require a hard-wired link between the transmitter and receiver, such as in fiber-optics. This includes line-of-sight systems such as traditional FSO and non-line-of-sight systems such as UV-based atmospheric scattering (see Related Links). It also includes ultra-short point-to-point systems (such as photonic chips and photonic chip packages), LAN systems, light-based broadcast Wi-Fi, and underwater communications.
OWC vs FSO
OWC is a broad term that encompasses any optical communication technology that uses freely propagating light to send a signal from one point to another. To qualify as OWC, the signal cannot be contained or guided in any way; fibers and waveguides disqualify a system from being classified as OWC. However, mirrors and other beam-steering devices do not disqualify a system from being classified as OWC.
FSO is a term specifically used when referring to optical communications performed for telecommunications purposes at 1064nm, 1310nm, or 1550nm depending on the industry standard. While FSO is based around satcom, telecommunications, and data structures, OWC can include all of those plus those listed in the Overview paragraph. FSO is thus a specific class of OWC, much like a Thunderbird is a specific class of Ford car.