FIBRE OPTIC COMMUNICATION PDF
PDF | A comprehensive study of the state-of-the-art fiber-optic communication systems is presented which can be used as both a textbook and. Fiber optic data transmission systems send information over fiber by turning electronic signals into light. ❑ Light refers to more than the portion of the. Fiber-Optic. Communication Systems. Third Edition. GOVIND E? AGRAWAL. The Institute of Optics. University of Rochester. Rochester: NY.
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Identify the basic components of a fiber optic communication system. • Discuss light propagation in an optical fiber. • Identify the various types of optical fibers. Main Characteristics of Fiber Optics Communication System. - Light propagation in of Plastic Fibers. (Source: resourceone.info). Fiber-Optic Communication Systems Third Edition GOVIND E?AGRAWAL The Institute of Optics University of Rochester Rochester:NY WILEY-.
Kao, a young engineer born in Shanghai and trained in Britain, inherited the optical waveguide project. He had already been analyzing what would happen if the optical waveguide was clad with a layer of transparent material with lower refractive index.
That cladding would confine the light within the fibermthe same conclusion O'Brien had reached a decade earlier. But Kao also found that if the difference between the refractive indexes of the core and the cladding was small, the core diameter could be increased to several micrometers and still transmit only a single mode.
That larger core would collect light much more easily, and confine light much better, than a tiny bare fiber. Bringing the guided light inside the fiber created a problem because the light had to go through the glass rather than air, which conventional wisdom held was inevitably more transparent. But Kao did not give up easily. Instead of asking how clear the best available glass was, he asked what 7Hecht, City of Light, Chapter 9.
Lasers Revive Optical Communications 9 was the fundamental lower limit on glass attenuation. Harold Rawson, a professor at the Sheffield Institute of Glass Technology in England, encouraged Kao with the information that impurities absorbed most of the light lost in standard glasses.
With a younger colleague, George Hockham, Kao wrote a paper outlining their case for a single-mode fiber-optic communication system, which he presented at a January 27, meeting of the Institution of Electrical Engineers in London and later published in Proceedings of the Institution of Electrical Engineers. The big problem was making a glass fiber as clear as they needed. Initial reactions were highly skeptical, and Bell Labs showed no interest.
But Kao attracted the interest of two British government agencies--the defense ministry and the Post Office's telecommunications division. Military contracts were a big part of STL's business, and the prospects for thin, flexible optical waveguides for use on the battlefield or inside military vehicles intrigued Don Williams of the Royal Signals Research and Development Establishment in Christchurch.
Optical transmission promised a big advantage in the emerging world of electronic warfare. Electronic systems were vulnerable to jamming by enemy equipment and could be disabled by powerful bursts of electromagnetic energy from nuclear explosions.
Optical transmission might present a way around those problems. It already was studying ideas for home phone customer access to remote computerized databases, a very early version of the Web.
Critically, its research budget had just received a big boost.
Fiber-Optic Communication Systems
The Post Office also found Kao another important connection--the Corning Glass Works, a long-time leader in glass research. The success of Kao's plan depended on removing impurities from glass, and that was a tough problem because ordinary glasses are made from inherently impure materials. However, Corning had earlier developed a technology for producing fused silica, which is essentially pure silicon dioxide.
Corning physicist Robert Maurer saw two key drawbacks to using fused silica. Its extremely high melting point made fiber fabrication hard, and its refractive index was lower than 8K.
Kao and G. Hockham, Dielectric-fiber surface waveguide for optical frequencies, Proceedings lEE , pp. But Maurer's gamble paid off. The same year also saw another crucial development. Researchers at the Ioffe Physics Institute in Russia and Bell Labs in the United States demonstrated the first semiconductor diode lasers the could operate continuously at room temperature within weeks of each other. Their lasers lasted only minutes, but that marked tremendous progress on tiny lasers that were a perfect match for the tiny cores of optical fibers.
Progress was also being made on LEDs, another potential light source. In , Richard Epworth, a young engineer just hired to work for Kao, used a laser to transmit black-and-white television signals through a meter m bundle of high-loss fibers crossing a large voltage differential. In mid, a top engineering manager, Stew Miller, described a future in which fibers would be used for in9F. Keck, and R. Maurer, Radiation losses in glass opticalwaveguides,Applied Physics Letters 17, pp.
Kessler, Fiber optics sharpens focus on laser communications, Electronics, pp. Lasers Revive Optical Communications 11 teroffice trunks less than about 10 km, and confocal waveguides would span tens of kilometers without repeaters.
Meanwhile, the first primitive fiber-optic links started coming into use. The technology was neither cheap nor easy, the links were short, and the applications were in difficult environments where interference or voltage differentials made electronic transmission impossible. Mostly they transmitted data from measurement instruments.
Arrays of 12 optical fibers were used to illuminate the holes in punched cards during the s. Computer uses at some major research universities and laboratories could access mainframes through remote terminals, but punched card input remained common into the early s.
Monopoly telephone carriers, led by the Bell System in the United States, defined the leading edge in telecommunications technology in the early s. The public impression of industry innovation was dominated by Bell's Picturephone video-telephone system, which proved a dismal failure.
But the crucial innovations reshaping the telephone system were deep inside the network. Starting in the s, carriers had begun converting internal transmission from the traditional analog format to digital signals, using the pulse-code modulation system Reeves had invented. The goal was to eventually convert all signals on the telephone network to digital form before multiplexing them for regional and long-distance transmission.
Bell carefully planned the details, setting the standard for four levels of digital multiplexing. Copper wires could carry the two lowest speeds, the 1. However, Bell made a few changes to match its requirements. Worried about the problems of coupling light into a core only a few micrometers across, Bell shifted to multimode fibers with cores of 50 or Miller, Optical communications research progress, Science , pp.
That gave up the advantage of single-mode transmission, but Bell thought it would be good enough for to km links. For a laser source, Bell picked nanometer nm gallium arsenide diode lasers, which were the most mature technology available. All in all, it was an entirely reasonable design, which Bell put through exhaustive testing and field trials. The problem was that Bell management expected to phase the new fiber-optic equipment in over many years, as the telephone monopoly planned with the millimeter waveguide, which it had started developing in Yet fiber technology did not stand still, making two key advances in short order.
And Masaharu Horiguchi at Nippon Telegraph and Telephone in Japan opened two new transmission windows in glass fibers, at 1. The new fibers also promised much higher bandwidth at 1. The new technology was a lifeline for the submarine cable group at Bell Labs, because their old coaxial cable technology could not keep up with satellite transmission. By they had begun developing the special-purpose technology needed for submarine fiber-optic cables, although the first transatlantic fiber cable was not laid until the end of But Bell management was not ready to give up on multimode fiber on land.
The critical push came from one of the upstart companies that had begun competing to carry long-distance traffic. Bell and other long-distance carriers followed, and soon single-mode fiber-optic networks spread across the country. Within a few years, data rates on the long-distance cables reached the gigabit range.
Yet the ideas did not go far in the data communications world.
The fundamental issue was cost. Sensors that vary the intensity of light are the simplest, since only a simple source and detector are required.
A particularly useful feature of such fiber optic sensors is that they can, if required, provide distributed sensing over distances of up to one meter. In contrast, highly localized measurements can be provided by integrating miniaturized sensing elements with the tip of the fiber. Extrinsic fiber optic sensors use an optical fiber cable , normally a multi-mode one, to transmit modulated light from either a non-fiber optical sensor—or an electronic sensor connected to an optical transmitter.
A major benefit of extrinsic sensors is their ability to reach otherwise inaccessible places. An example is the measurement of temperature inside aircraft jet engines by using a fiber to transmit radiation into a radiation pyrometer outside the engine.
Extrinsic sensors can be used in the same way to measure the internal temperature of electrical transformers , where the extreme electromagnetic fields present make other measurement techniques impossible. Extrinsic sensors measure vibration, rotation, displacement, velocity, acceleration, torque, and torsion.
A solid state version of the gyroscope, using the interference of light, has been developed. The fiber optic gyroscope FOG has no moving parts, and exploits the Sagnac effect to detect mechanical rotation. Common uses for fiber optic sensors includes advanced intrusion detection security systems. The light is transmitted along a fiber optic sensor cable placed on a fence, pipeline, or communication cabling, and the returned signal is monitored and analyzed for disturbances.
This return signal is digitally processed to detect disturbances and trip an alarm if an intrusion has occurred. Optical fibers are widely used as components of optical chemical sensors and optical biosensors. A frisbee illuminated by fiber optics Light reflected from optical fiber illuminates exhibited model Optical fibers have a wide number of applications.
They are used as light guides in medical and other applications where bright light needs to be shone on a target without a clear line-of-sight path. In some buildings, optical fibers route sunlight from the roof to other parts of the building see nonimaging optics.
Optical-fiber lamps are used for illumination in decorative applications, including signs , art , toys and artificial Christmas trees. Optical fiber is an intrinsic part of the light-transmitting concrete building product LiTraCon.
Optical fiber can also be used in structural health monitoring. This type of sensor is able to detect stresses that may have a lasting impact on structures. It is based on the principle of measuring analog attenuation.
Use of optical fiber in a decorative lamp or nightlight Optical fiber is also used in imaging optics. A coherent bundle of fibers is used, sometimes along with lenses, for a long, thin imaging device called an endoscope , which is used to view objects through a small hole.
Medical endoscopes are used for minimally invasive exploratory or surgical procedures. Industrial endoscopes see fiberscope or borescope are used for inspecting anything hard to reach, such as jet engine interiors. Many microscopes use fiber-optic light sources to provide intense illumination of samples being studied. In spectroscopy , optical fiber bundles transmit light from a spectrometer to a substance that cannot be placed inside the spectrometer itself, in order to analyze its composition.
A spectrometer analyzes substances by bouncing light off and through them. By using fibers, a spectrometer can be used to study objects remotely. Rare-earth-doped optical fibers can be used to provide signal amplification by splicing a short section of doped fiber into a regular undoped optical fiber line.
The doped fiber is optically pumped with a second laser wavelength that is coupled into the line in addition to the signal wave.
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Both wavelengths of light are transmitted through the doped fiber, which transfers energy from the second pump wavelength to the signal wave. The process that causes the amplification is stimulated emission. Optical fiber is also widely exploited as a nonlinear medium. POF is a newer plastic-based cable which promises performance similar to glass cable on very short runs, but at a lower cost.
Multimode fiber gives you high bandwidth at high speeds 10 to MBS - Gigabit to m to 2km over medium distances. Light waves are dispersed into numerous paths, or modes, as they travel through the cable's core typically or nm. Typical multimode fiber core diameters are 50, However, in long cable runs greater than feet [ Today's optical fiber attenuation ranges from 0.
Attenuation limits are based on intended application. The applications of optical fiber communications have increased at a rapid rate, since the first commercial installation of a fiber-optic system in Telephone companies began early on, replacing their old copper wire systems with optical fiber lines.
Today's telephone companies use optical fiber throughout their system as the backbone architecture and as the long-distance connection between city phone systems.
Cable television companies have also began integrating fiber-optics into their cable systems. The trunk lines that connect central offices have generally been replaced with optical fiber. Such a hybrid allows for the integration of fiber and coaxial at a neighborhood location. This location, called a node, would provide the optical receiver that converts the light impulses back to electronic signals.
The signals could then be fed to individual homes via coaxial cable. Local Area Networks LAN is a collective group of computers, or computer systems, connected to each other allowing for shared program software or data bases. Colleges, universities, office buildings, and industrial plants, just to name a few, all make use of optical fiber within their LAN systems.
Power companies are an emerging group that have begun to utilize fiber-optics in their communication systems. Most power utilities already have fiber-optic communication systems in use for monitoring their power grid systems.
Fiber by John MacChesney - Fellow at Bell Laboratories, Lucent Technologies Some 10 billion digital bits can be transmitted per second along an optical fiber link in a commercial network, enough to carry tens of thousands of telephone calls.
Hair-thin fibers consist of two concentric layers of high-purity silica glass the core and the cladding, which are enclosed by a protective sheath. Light rays modulated into digital pulses with a laser or a light-emitting diode move along the core without penetrating the cladding.
Refinements in optical fibers, along with the development of new lasers and diodes, may one day allow commercial fiber-optic networks to carry trillions of bits of data per second. Total internal refection confines light within optical fibers similar to looking down a mirror made in the shape of a long paper towel tube.
Because the cladding has a lower refractive index, light rays reflect back into the core if they encounter the cladding at a shallow angle red lines.NASA went so far as to test lasers for transmitting signals between ground and space or between two spacecraft, but the results were discouraging.
Each possible phase constant 13represents a mode. Connecting a pair of computers with fiber required not just the fiber, but also a transmitter that converted electronic input to optical output, and a receiver that converted optical input to electronic output.
Fibers also found their way into some nonmilitary applications with difficult requirements. Engineers overcame earlier difficulties with pulse-spreading at that wavelength using conventional InGaAsP semiconductor lasers.
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