Free Space Optics (FSO)
Optical communications does not necessarily require fibers. Wireless optical networks, based on use of free space as transmission medium and low power lasers as light sources, have become a major commercial breakthrough. The lasers are not aggressive to the environment and nor to the people as well as they are less dangerous than a laser pen.
FSO first appeared in the 60's, for military applications. At the end of 80's, it appeared as a commercial option but technological restrictions prevented it from success. Low reach transmission, low capacity, severe alignment problems as well as vulnerability to weather interferences were the major drawbacks at that time. The optical communication without wire, however, evolved! Today, FSO systems guarantee 2.5 Gb/s rates with carrier class availability. Metropolitan, access and LAN networks are reaping the benefits. FSO success can be measured by its market numbers: forecasts predict it will reach a US$ 2.5 billion market by 2006.
The use of free space optics is particularly interesting when we perceive that the majority of customers does not possess access to fibers as well as fiber installation is expensive and demands long time. Moreover, right-of-way costs, difficulties in obtaining government licenses for new fiber installation are further problems that has turned FSO into the option of choice for short reach applications.
Main applications of free space optics are last mile broadband access, connection to metropolitan optical networks, ring closing, back-up and redundancy for optical path, river and highway crossings, linking LAN's between buildings, PCS/WLL backhaul and other urban applications.
FSO advantages
FSO advantages are many - lower costs as compared to fiber networks, easiness and speed of installation, high transmission capacity, network protocol transparency, right-of-way free, licence-free installation, licence-free frequency band, low risk investment, fast revenue generation etc. FSO costs are as low as 1/5 of fiber network costs while installation takes no longer than 2 to 3 days (fiber may demand 6 to 12 months of work).
FSO architectures
Three main FSO architectures have been used so far. Point-to-point architecture is a dedicated connection that offers higher bandwidth but is less scalable. Mesh architectures may offer redundancy and higher reliability with easy node addition but restrict distances more than the other options. Point-to-multipoint architecture offers cheaper connections and facilitates node addition but at the expense of lower bandwidth than the point-to-point option.
| Ponto-to-point architecture |
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| Mesh architecture |
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| Point-to-multipoint architecture |
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