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Sample essay topic, essay writing: Fiber Optics - 1146 words
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Fiber OpticsFiber Optic Cable Facts'A relatively new technology with vast potential importance, fiber optics is thechanneled transmission of light through hair-thin glass fibers.'[ Less expensive than copper cables[ Raw material is silica sand[ Less expensive to maintain If damaged, restoration time is faster(although more users are affected)[ Backbone to the Information SuperhighwayInformation (data and voice) is transmitted through the fiber digitally bythe use of high speed LASERs (Light Amplification through the Simulated Emissionof Radiation) or LEDs (Light Emitting Diodes). Each of these methods create ahighly focused beam of light that is cycled on and off at very high speeds.Computers at the transmitting end convert data or voice into 'bits' ofinformation. The information is then sent through the fiber by the presence, orlack, of light. Computers on the receiving end convert the light back into dataor voice, so it can be used.ORIGIN OF FIBER OPTICSInformation (data and voice) is transmitted through the fiber digitally bythe use of high speed LASERs (Light Amplification through the Simulated Emissionof Radiation) or LEDs (Light Emitting Diodes). Each of these methods create ahighly focused beam of light that is cycled on and off at very high speeds.Computers at the transmitting end convert data or voice into 'bits' ofinformation.
The information is then sent through the fiber by the presence, orlack, of light. So, all of the data is sent light pulses. Computers on thereceiving end convert the light back into data or voice, so it can be used.All of this seems to be a very 'modern' concept, and the technology we useis. The concept though, was the idea of Alexander Graham Bell in the late 1800's.He just didn't have a dependable light source.. some days the sun doesn'tshine! He thought of the idea that our voices could be transmitted by pulses oflight
The people who thought that audio, video, and other forms of data couldbe transmitted by light through cables, were present day scientists. Most ofthe things that are possible today, Alexander Grahm Bell could never even havedreamed of.Although the possibility of lightwave communications occurred to AlexanderGraham Bell (who invented the telephone), his ideas couldn't be used until theLASER or LED had been invented. Most of these advances occurred in the 1970s,and by 1977 glass-purifying and other fiber-optic manufacturing techniques hadalso reached the stage where interoffice lightwave communications were possible.With further technological development, many intercity routes were in operationby 1985, and some transoceanic routes had been completed by 1990. Now, in themid-90's, worldwide connections are possible through the Internet.The light is prevented from escaping the fiber by total internalreflection, a process that takes place when a light ray travels through a mediumwith an Index of Refraction higher than that of the medium surrounding it. Herethe fiber core has a higher refractive index than the material around the core,and light hitting that material is reflected back into the core, where itcontinues to travel down the fiber.THE PROPAGATION OF LIGHT AND LOSS OF SIGNALSThe glass fibers used in present-day fiber-optic systems are based onultrapure fused silica (sand).
Fiber made from ordinary glass is so dirty thatimpurities reduce signal intensity by a factor of one million in only about 16ft of fiber. These impurities must be removed before useful long-haul fibers canbe made. But even perfectly pure glass is not completely transparent. It weakenslight in two ways. One, occurring at shorter wavelengths, is a scattering causedby unavoidable density changes within the fiber.
In other words, when the lightchanges mediums, the change in density causes interference. The other is alonger wavelength absorption by atomic vibrations. For silica, the maximumtransparency, occurs in wavelengths in the near infrared, at about 1.5 m(micrometers).APPLICATIONSFiber-optic technology has been applied in many areas, although itsgreatest impact has come in the field of telecommunications, where optical fiberoffers the ability to transmit audio, video, and data information as coded lightpulses. Fiber optics are also used in the field of medicine, all of the wire-cameras and lights are forms of fiber optic cable. In fact, fiber optics havequickly become the preferred mode of transmitting communications of all kinds.Its advantages over older methods of transmitting data are many, and includegreatly increased carrying capacity (due to the very high frequency of light),lower transmission losses, lower cost of basic materials, much smaller cablesize, and almost complete immunity to any interference.
Other applicationsinclude the simple transmission of light for illumination in awkward places,image guiding for remote viewing, and sensing.ADVANTAGES OF FIBER OPTIC CABLEThis copper cable contains 3000 individual wires.It takes two wires to handle one two-way conversation.That means 1500 calls can be transmitted simultaneously on each cable.Each fiber optic cable contains twelve fiber wires.Two fibers will carry the same number of simultaneous conversations as one wholecopper cable.Therefore, this fiber cables replace six of the larger ones.And 90,000 calls can be transmitted simultaneously on one fiber optic cable.LONG DISTANCEFIBER-OPTIC COMMUNICATIONS SYSTEMSAT&T's Northeast Corridor Network, which runs from Virginia toMassachusetts, uses fiber cables carrying more than 50 fiber pairs. Using asemiconductor LASER or a light-emitting diode (LED) as the light source, atransmitter codes the audio or visual input into a series of light pulses,called bits. These travel along a fiber at a bit-rate of 90 million bits persecond (or 90 thousand kbps). Pulses need boosting, about every 6.2 miles, andfinally reach a receiver, containing a semiconductor photodiode detector (lightsensor), which amplifies, decodes, and regenerates the original audio or visualinformation. Silicon integrated circuits control and adjust both transmitter andreceiver operations.THE FUTURE OF FIBER OPTICSLight injected into a fiber can adopt any of several zigzag paths, or modes.When a large number of modes are present they may overlap, for each mode has adifferent velocity along the fiber.
Mode numbers decrease with decreasing fiberdiameter and with a decreasing difference in refractive index between the fibercore and the surrounding area. Individual fiber production is quite practical,and today most high-capacity systems use single fibers. The present pace oftechnological advance remains impressive, with the fiber capacity of new systemsdoubling every 18 to 24 months. The newest systems operate at more than twobillion bits per second per fiber pair. During the 1990s optical fibertechnology is expected to extend to include both residential telephone and cabletelevision service.Currently Bell South is placing fiber cables containing up to 216 fibers,and manufacturers are starting to build larger ones. Bell South has beenplacing fiber cables in the Orlando area since the early 1980s, and currentlyhas hundreds of miles in service to business and residential customers.BIBLIOGRAPHY1. 1995 Grolier Multimedia Encyclopedia, Grolier Electronic Publishing, Inc.2. 1994 Compton's Interactive Encyclopedia, Compton's NewMedia.3. Fiber Optics abd Lightwave Communications Standard Dictionary, Martin H.Weik, D.Sc., Van Nostrand Reinhold Company, New York, New York, 1981.4. Fiber Optics and Laser Handbook, 2nd Edition, Edward L.
Stafford, Jr. andJohn A. McCann, Tab Books, Inc., Blue Ridge Summit, Pennsylvania, 1988.5. Fiber Optics and Optoelectronics, Second Edition, Peter K. Cheo, PrenticeHall, Englewood Cliffs, New Jersey, 1990.
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