Free Space Optics

The first know use of Free Space optics was when the ancient Greeks used polished shields during battle to send signals to troops on the battle field using the light from the sun, Semaphores in more recent time allowed more complex messages to be sent and then in 1880 Alexander Graham Bell created the Photophone which allowed for the transmission of sound on a beam of light.

On June the 3rd 1880 he conducted the first wireless telephone call in history using this method. The invention of lasers in the 1960's revolutionised free space optics and led us to the modern products.

FSO Links today

Modern laser links allows the transmission of data through the air by modulating the wavelength of the laser light, these methods allow for high bandwidths to be achieved, typically 100Mbps or 1Gbps although there have been 10Gbps products on the market in the past - and rumours of another 10Gbps product in development at the moment. The most common use of FSO links is to link 2 building together as a bridge between 2 LAN segments – although I know of a deployment in a fleet of police cars in the USA for fast data download from the cars internal cameras to the station when the cars park in designated bays. FSO links are also used as a backup to traditional Fibre networks.

Modern laser links can provide 1Gbps throughput at distances of up to 5000M when deployed in the correct environment.

Pro and Cons.

As with any technology there are pros and cons to it. Laser links are an excellent product and when deployed correctly give high reliability and excellent value for money:-

Advantages

• Excellent bandwidth to cost ratio – FSO links are a very cost effective way to provide high bandwidth links over short distances
• License free operation – many radio links require licenses.
• High Bandwidth
• Low error rates
• Full Duplex communications
• Are not effected by interference
• Inherently secure
• No Fresnel zone clearance required – only direct line of sight

Disadvantages

• Mounting – lasers require a very firm mounting location making them unsuitable for tower and mast mounting.
• Can be effected by atmospheric conditions – rain, fog etc – although this is becoming less of an issue with modern links. Snow can build up on incorrectly installed units.
• Limited life – the laser diodes using in FSO links have a limited life before they fail, typically about 7-8 years in comparison radio links can last much longer.

Summary

Laser links are a cost effective way of providing high-bandwidth solutions, over relatively short distances, and when installed correctly give secure, reliable, full duplex links. If you need help in determining if FSO technology is right for your business then please speak to us. As one of the largest and most experienced companies in the UK for Laser deployments we can advise on the whole process or offer or comprehensive design, install support service.