FSO Overview and Key Terms
Free-Space Optics (FSO) communication, also called free-space optical communication, is an optical communication technology that uses light propagating in free space to wirelessly send a signal. For example, using a flashlight and turning it off and on to send Morse code is FSO communication. Another example is using a laser rapidly turning off and on to send digital 0’s and 1’s to a receiver. FSO does not use fiber-optic cables or wires to send information. To be FSO, light must propagate in free space such as air or a vacuum.
FSO is encompassed under the umbrella term “optical wireless communication” (OWC). FSO differs from OWC in that FSO usually refers specifically to telecommunications done in the infrared waveband. Most FSO communication is done using a laser operating at 1064nm, 1310nm, or 1550nm depending on the standard applied.
- Attenuation: the loss of a signal’s power through certain means. In FSO, attenuation is most common in adverse weather conditions like rain, snow, and especially fog.
- Downlink: sending a signal from a satellite to a ground station.
- Modulation: changing the phase, frequency, or amplitude of one signal with another signal.
- Scintillation: an optical effect that causes a point source to appear to flicker and jitter due to differences in air temperature.
- Uplink: sending a signal from a ground station to a satellite.