Mention optical communication and most people think of fiber optics. But
light travels through air for a lot less money. So it is hardly a surprise that
clever entrepreneurs and technologists are borrowing many of the devices and techniques
developed for fiber-optic systems and applying them to what some call fiber-free
optical communication. Although it only recently, and rather suddenly, sprang
into public awareness, free-space optics is not a new idea. It has roots that
go back over 30 years--to the era before fiber-optic cable became the preferred
transport medium for high-speed communication. In those days, the notion that
FSO systems could provide high-speed connectivity over short distances seemed
futuristic, to say the least. But research done at that time has made possible
today's free-space optical systems, which can carry full-duplex (simultaneous
bidirectional) data at gigabit-per-second rates over metropolitan distances of
a few city blocks to a few kilometers.
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 taxes with carrier class availability. Metropolitan, access and LAN networks
are reaping the benefits.
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
obataining government licenses for new fiber installation etc. are further problems
that has turned FSO into the option of choice for short reach applications.
FSO uses lasers, or light pulses, to send packetized data in the terahertz (THz)
spectrum range. Air, ot fiber, is the transport medium. This means that urban
businesses needing fast data and Internet access have a significantly lower-cost
FSO technology is implemented using a laser device .These laser devices or terminals
can be mounted on rooftops ,Corners of buidings or even inside offices behind
windows. FSOdevices look like security video cameras.
beams, which do not harm the eyes, are the means by which free-space optics technology
transmits data through the air between transceivers, or link heads, mounted on
rooftops or behind windows. It works over distances of several hundred meters
to a few kilometers, depending upon atmospheric conditions.
free-space optics equipment provides data rates much higher than digital subscriber
lines or coaxial cables can ever hope to offer. And systems even faster than the
present range of 10 Mb/s to 1.25 Gb/s have been announced, though not yet delivered.
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