Free-space optical communication

The optical links usually use laser light, althogh low-data-rate communication over short distances is possible using LEDs. IrDA is a very simple form of free-space optical communications.

For longer distances, a pair of telescopes is used at each end, with a laser and photosensors mounted in each telescope.

Free-space optical communications has a number of uses:

• as a last mile[?] telecommunications link
• as a LAN link between buildings
• for communications between spacecraft, including elements of a satellite constellation
• for interstellar communication

For terrestrial applications, the limiting factors are the attenuation of the beam by:

• beam dispersion[?]
• atmospheric absorption
• rain (severe rain may have up to 100 dB/km attenuation)
• fog
• snow
• scintillation

For space applications, none of these defects applies, and free-space optical communications is potentially usable at interstellar distances.

See also: optical window, radio window[?], Free-space loss, Rayleigh scattering, Mie scattering

References

• Kontogeorgakis, Christos; Millimeter Through Visible Frequency Waves Through Aerosols-Particle Modeling, Reflectivity and Attenuation

External links

• http://www.irda.org/