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Free Space Optics

From Biocrawler, the free encyclopedia.

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Free Space Optics (FSO) is a telecommunication technology that uses light, typically infrared laser light to transmit voice, data and video wireless up to 1..2 miles. Because of the use of lasers, Free Space Optics delivers high speed data communications at fiber speed. There are products commercially available which support up to 2.5 Gbit/s. Free Space Optics can be used in situations when high speed connections are needed and fiber optics would not be available or expensive.

Contents

1 Applications

2 History

3 Technology advantages and behavior

4 Advantages and Challenges

5 Literature

6 Weblinks

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Applications

Typically scenarios for use are:

LAN-to-LAN connections on campuses at FastEthernet or GigabitEthernet speeds
LAN-to-LAN connections in a city
To cross a road or other barriers
Speedy service delivery of high bandwdth access to fiber networks
Converged Voice-Data-Connection
Temporary network installation (for events or other purposes)
Reestablish high speed connection quickly (Disaster Recovery)
As an alternative or upgrade addon to existing wireless technologies.
As an safety addon for important fiber connections (redundancy)

The lightbeam is very narrow, which makes that kind of wireless transmission secure. FSO provides best EMI behaviour using light instead of microwaves.

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History

Beginning with laser developments in the 1960s first serious trials started to develop "Lightphones". Especially military organisations were interested and forced some developments. During the boom of optical fibers the FSO technology slept for a while in engineers' files..But in military and space laboratories the development didn't really stop. Some features of the FSO technology were important for military and become again important for civil use.

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Technology advantages and behavior

FSO is a technology, which allows transparent data transmission. Because if using light, FSO could theoretically reach nearly the same high data rates as optical fiber can transmit. As every wireless technology FSO has to deal with several influences in the atmosphere, as there are:

Scintillation
Background light
Shadowing
Weather
Pollution / smog

These impacts cause an attenuated receive signal and/or higher bit error rates. To overcome these issues, vendors found some solutions, like an multibeam or multipath architecture, which uses more than one sender and more than one receiver. Some state-of-the-art devices also have a bigger fade margins (extra power, reserved for rain, smog, fog). To keep the a healthy environment, good FSO systems have a limited laser power density and support laser classes 1 or 1M.

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Advantages and Challenges

Main Advantages are:

Quick link setup
license free operation
High transmission security
High bit rates
No fresnel zone necessary
Low snow and rain impact
Full duplex transmission
Protocol transparency
No interfrence
Great EMI behavior

Also microwave radio has some advantages which are a bigger distance and less attenuation by fog. Both technologies have the economical advantage that a cable investment wouldn't being stuck into the ground.

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