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.
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 taxes 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 USS 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 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 option.
An FSO system for local loop access comprises several laser terminals, each one residing at a network node to create a single, point-to-point link; an optical mesh architecture; or a star topology, which is usually point-to-multipoint. These laser terminals, or nodes, are installed on top of customers' rooftops or inside a window to complete the last-mile connection. Signals are beamed to and from hubs or central nodes throughout a city or urban area. Each node requires a Line-Of-Sight (LOS) view of the hub.
Free space optics (FSO) is a line- of- site technology that uses lasers to provide optical bandwidth connections.
Is capable of 2.5 Gbps of data,voice and video communications.
The use of lasers is a simple concept similar to optical transmissions using fiber-optic cables;the only difference is the medium.
FSO Technology
Is based on connectitvity between FSO units, each consisting of an optical transceiver with a laser transmitter and a receiver to provide full duplex(bi-directional) capability.
Requires no spectrum licensing.
Is easily upgradeable, which helps service providers protect their investment in embedded telecommunications infrastructures.
How it works
FSO involves the optical transmission of voice, video, and data using air as the medium of transmission as opposed to fiber optic cable.
Involves two systems each consisting of an optical trasnsceiver which consist of a laser transmitter and a receiver to provide full duplex (bi -directional) capability.
Wireless or optical
FSO is clearly an optical technology and not a wireless technology for two primary reasons.
It enables optical transmission at speeds of up to 2.5 Gbps and in the future 10 Gbps u using WDM.
Also it obviates the need to buy expensive spectrum, which distinguishes it clearly from fixed wireless technologies.
Challenges
FSO is also a line-of-site technology and interconnecting points must br free from physical obstruction and able "see" each other.
Rain and snow have little effect on FSO:
The major challenge to FSO communication is fog.
The primary way to counter fog when deploying FSO is through a network design that shortens FSO link distances and adds network redundancies.
Safety
With FSO, safety is often a concern because the technology uses lasers for transmission.
Human exposure to laser beams (which present much more danger to the eyes than any other part of the human body).
0 comments:
Post a Comment