Freespace Optical Communication Systems

Freespace Optical Communication Systems

Freespace optical communication (FSO) systems are an alternative to optical fiber systems and microwave systems for short distances

FSO systems transmit infrared optical signals through the air.
FSO systems support higher data rates than microwave systems, but over much shorter distances.

FSO systems can be an effective technology for spanning 250 meters to 4 km (2.5 miles), where direct line of sight is available between buildings

But it is very difficult to deliver 99.999% reliability
Use dual homing & meshing to improve reliability

This image shows two office buildings. On the roof of each building is an optical communication system. The pair of systems send infrared light signals through the air between the buildings.

Challenges include:

Atmospheric absorption – fog, smog, rain can knock out signal >>30 dB loss
Scintillation (heat waves / heat haze) – large dynamic range required
Vibrations – auto tracking servos
Line of sight obstructions – birds etc.

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