Optical Fibre

description of optical fiber
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  Optical fiber   From Wikipedia, the free encyclopedia A bundle of optical fibers Fiber crew installing a 432-count fiber cable underneath the streets of Midtown Manhattan, New York City A TOSLINK  fiber optic audio cable with red light being shone in one end transmits the light to the other end   A wall-mount cabinet containing optical fiber interconnects. The yellow cables are single mode fibers; the orange and aqua cables are multi-mode fibers: 50/125 µm OM2 and 50/125 µm OM3 fibers respectively. An optical fiber  or optical fibre  is a flexible, transparent fiber made by drawing glass (silica) or  plastic to a diameter slightly thicker than that of a human hair . [1]  Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher  bandwidths (data rates) than wire cables. Fibers are used instead of  metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a  problem from which metal wires suffer excessively. [2]  Fibers are also used for  illumination and imaging, and are often wrapped in bundles so that they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. [3]  Specially designed fibers are also used for a variety of other applications, some of them being fiber optic sensors and fiber lasers. [4]  Optical fibers typically include a core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of  total internal reflection which causes the fiber to act as a waveguide. [5]  Fibers that support many propagation paths or transverse modes are called multi-mode fibers, while those that support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a wider core diameter  [6]  and are used for short-distance communication links and for applications where high power must be transmitted. [ citation needed  ]  Single-mode fibers are used for most communication links longer than 1,000 meters (3,300 ft). [ citation needed  ]  Being able to join optical fibers with low loss is important in fiber optic communication. [7]  This is more complex than joining electrical wire or cable and involves careful cleaving of the fibers,  precise alignment of the fiber cores, and the coupling of these aligned cores. For applications that demand a permanent connection a fusion splice is common. In this technique, an electric arc is used to melt the ends of the fibers together. Another common technique is a mechanical splice,  where the ends of the fibers are held in contact by mechanical force. Temporary or semi- permanent connections are made by means of specialized optical fiber connectors. [8]    The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics . The term was coined by Indian physicist  Narinder Singh Kapany, who is widely acknowledged as the father of fiber optics. [9]   Contents    1 History  o   1.1 Record speeds     2 Uses  o   2.1 Communication  o   2.2 Sensors  o   2.3 Power transmission  o   2.4 Other uses     3 Principle of operation  o   3.1 Index of refraction  o   3.2 Total internal reflection  o   3.3 Multi-mode fiber   o   3.4 Single-mode fiber   o   3.5 Special-purpose fiber      4 Mechanisms of attenuation  o   4.1 Light scattering  o   4.2 UV-Vis-IR absorption  o   4.3 Loss budget     5 Manufacturing  o   5.1 Materials  o   5.2 Process  o   5.3 Coatings     6 Practical issues  o   6.1 Cable construction  o   6.2 Termination and splicing  o   6.3 Free-space coupling  o   6.4 Fiber fuse  o   6.5 Chromatic dispersion     7 See also     8 References     9 Further reading     10 External links  History   Daniel Colladon first described this light fountain or light pipe in an 1842 article titled On the reflections of a ray of light inside a parabolic liquid stream . This particular illustration comes from a later article by Colladon, in 1884. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon and Jacques Babinet in Paris in the early 1840s. John Tyndall  included a demonstration of it in his public lectures in London, 12 years later . [10]  Tyndall also wrote about the property of  total internal reflection in an introductory book about the nature of light in 1870: When the light passes from air into water, the refracted ray is bent towards  the  perpendicular ... When the ray passes from water to air it is bent  from  the perpendicular... If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the ray will not quit the water at all: it will be totally reflected   at the surface.... The angle which marks the limit where total reflection begins is called the limiting angle of the medium. For water this angle is 48°27′, for flint glass it is 38°41′, while for diamond it is 23°42′. [11][12]  In the late 19th and early 20th centuries, light was guided through bent glass rods to illuminate  body cavities. [13]  Practical applications such as close internal illumination during dentistry appeared early in the twentieth century. Image transmission through tubes was demonstrated independently by the radio experimenter  Clarence Hansell and the television pioneer  John Logie Baird in the 1920s. In the 1930s, Heinrich Lamm showed that one could transmit images through a bundle of unclad optical fibers and used it for internal medical examinations, but his work was largely forgotten. [10][14]  In 1953, Dutch scientist Bram van Heel first demonstrated image transmission through bundles of optical fibers with a transparent cladding. [14]  That same year, Harold Hopkins and  Narinder
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