11-09-2013, 12:41 PM
Fibre Optics
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What are Optical Fibres?
Optical Fibres are fibres of glass, usually about 120 micrometers in diameter, which are used to carry signals in the form of pulses of light over distances up to 50 km without the need for repeaters. These signals may be coded voice communications or computer data.
History
Interest in the use of light as a carrier for information grew in the 1960's with the advent of the laser as a source of coherent light. Initially the transmission distances were very short, but as manufacturing techniques for very pure
glass arrived in 1970, it became feasible to use optical fibres as a practical transmission medium. At the same time developments in semi-conductor light sources and detectors meant that by 1980 worldwide installation of fibre optic communication systems had been achieved.
Advantages:
Capacity
Optical fibres carry signals with much less energy loss than copper cable and with a much higher bandwidth . This means that fibres can carry more channels of information over longer distances and with fewer repeaters required.
Attenuation:
No attenuation or power loss during transmission through the cables.
Size and Weight
Optical fibre cables are much lighter and thinner than copper cables with the same bandwidth. This means that much less space is required in underground cabling ducts. Also they are easier for installation engineers to handle.
Security
Optical fibres are much more difficult to tap information from undetected; a great advantage for banks and security installations. They are immune to Electromagnetic interference(EMI) from radio signals, lightning etc. They can be routed safely through explosive or flammable atmospheres, for example, in the petrochemical industries or munitions sites, without any risk of ignition.
Optical Fibre Sensors
Many advances have been made in recent years in the use of Optical Fibres as sensors. Gas concentration, chemical concentration, pressure, temperature, and rate of rotation can all be sensed using optical fibre.
How to prepare the Fibre Optics
Optical fibes are made up of glass or transparent plastic, quartz, nylone or polystyrene. Optical fibres are thin hair like solid strength that carries light along their length by process of multiple total internal reflections.
In this process beam of light entering at one end transmitted along the fibre without loss of intensity whether the fibre is straight or band to the curve.
The signal carrying capacity of light wave is much greater than that of radio waves along proper wire therefore a light wave traveling in fibre can carry thousand times more information compared to the radio waves.