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Encyclopedia > Optical fiber
Optical fibers
Optical fibers

An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communication, which permits transmission over longer distances and at higher data rates than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are immune to electromagnetic interference. Optical fibers are also used to form sensors, and in a variety of other applications. This is a file from the Wikimedia Commons, a repository of free content hosted by the Wikimedia Foundation. ... This is a file from the Wikimedia Commons, a repository of free content hosted by the Wikimedia Foundation. ... This article is about the material. ... For other uses, see Plastic (disambiguation). ... For other uses, see Light (disambiguation). ... For the song by 311, see Grassroots Applied science is the exact science of applying knowledge from one or more natural scientific fields to practical problems. ... Engineering is the discipline and profession of applying scientific knowledge and utilizing natural laws and physical resources in order to design and implement materials, structures, machines, devices, systems, and processes that realize a desired objective and meet specified criteria. ... Fiber-optic communication is a method of transmitting information from one place to another by sending light through an optical fiber. ... This article is about Physics. ... Electromagnetic interference (or EMI, also called radio frequency interference or RFI) is a (usually undesirable) disturbance caused in a radio receiver or other electrical circuit by electromagnetic radiation emitted from an external source. ... Not to be confused with censure, censer, or censor. ...


Light is kept in the "core" of the optical fiber by total internal reflection. This causes the fiber to act as a waveguide. Fibers which support many propagation paths or transverse modes are called multimode fibers (MMF). Fibers which support only a single mode are called singlemode fibers (SMF). Multimode fibers generally have a large-diameter core, and are used for short-distance communication links or for applications where high power must be transmitted. Singlemode fibers are used for most communication links longer than 200 meters. Critical angle redirects here. ... In electromagnetics and communications engineering, a waveguide is defined as any physical structure that guides electromagnetic waves. ... A transverse mode of a beam of electromagnetic radiation is a particular intensity pattern of radiation measured in a plane perpendicular (i. ... Multi-mode optical fiber (multimode fiber or MM fiber or fibre) is a type of optical fiber mostly used for communication over shorter distances, such as within a building or on a campus. ... In fiber-optic communication, a single-mode optical fiber (SMF) is an optical fiber designed to carry only a single ray of light (mode). ...


Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together either mechanically or by fusing them together with an electric arc. Special connectors are used to make removable connections. A mechanical splice is an optical junction of two (or more) optical fibers that are aligned and held in place by a self-contained assembly (usually the size of a large carpenters nail). ... A 3000 volt electricity arc between two nails Electricity arcs between the power rail and electrical pickup shoe on a London Underground train An electric arc can melt calcium oxide An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current... An optical fiber connector constitutes a fiber-to-fiber interconnection and aligns the fiber core of two optical fibers. ...

Contents

History

The light-guiding principle behind optical fibers was first demonstrated by Daniel Colladon and Jacques Babinet in Paris in the 1840s, with Irish inventor John Tyndall offering public displays using water-fountains ten years later.[1] 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. The principle was first used for internal medical examinations by Heinrich Lamm in the following decade. In 1952, physicist Narinder Singh Kapany conducted experiments that led to the invention of optical fiber, based on Tyndall's earlier studies; modern optical fibers, where the glass fiber is coated with a transparent cladding to offer a more suitable refractive index, appeared later in the decade.[1] Development then focused on fiber bundles for image transmission. The first fiber optic semi-flexible gastroscope was patented by Basil Hirschowitz, C. Wilbur Peters, and Lawrence E. Curtiss, researchers at the University of Michigan, in 1956. In the process of developing the gastroscope, Curtiss produced the first glass-clad fibers; previous optical fibers had relied on air or impractical oils and waxes as the low-index cladding material. A variety of other image transmission applications soon followed. The advent of ultrapure silicon for semiconductor devices made low-loss silica fiber practical. Jean-Daniel Colladon (born on 15 December 1802 in Geneva and died on 30 June 1893), was a Swiss physicist. ... Jacques Babinet (b. ... John Tyndall. ... Clarence Weston Hansell was an American research engineer who pioneered investigation into the biological effects of ionized air. ... For other persons named John Baird, see John Baird (disambiguation). ... ‹The template below has been proposed for deletion. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... Basil Hirschowitz is an academic Gastroenterologist best known in the field for having invented an improved optical glass fiber which allowed the creation of a useful flexible endoscope. ... The University of Michigan, Ann Arbor (U of M, UM, U-M or simply Michigan) is a coeducational public research university in the state of Michigan. ...


In 1965, Charles K. Kao and George A. Hockham of the British company Standard Telephones and Cables were the first to suggest that attenuation of contemporary fibers was caused by impurities, which could be removed, rather than fundamental physical effects such as scattering. They speculated that optical fiber could be a practical medium for communication, if the attenuation could be reduced below 20 dB per kilometer.[2] This attenuation level was first achieved in 1970, by researchers Robert D. Maurer, Donald Keck, Peter C. Schultz, and Frank Zimar working for American glass maker Corning Glass Works, now Corning Inc. They demonstrated a fiber with 17 dB optic attenuation per kilometer by doping silica glass with titanium. A few years later they produced a fiber with only 4 dB/km using germanium oxide as the core dopant. Such low attenuations ushered in optical fiber telecommunications and enabled the Internet. Nowadays, attenuations in optical cables are far less than those in electrical copper cables, leading to long-haul fiber connections with repeater distances of 500–800 km. Charles Kuen Kao, Ph. ... Standard Telephones and Cables Ltd (later STC plc) was a British telephone, telegraph, radio, telecommunications and related equipment R&D manufacturer. ... Attenuation is the decrease in intensity of electromagnetic radiation due to absorption or scattering of photons. ... For other uses, see Decibel (disambiguation). ... Peter C. Schultz, Ph. ... Corning Glass Works (NYSE: GLW) is a U.S. manufacturer of glass, ceramics and related materials, primarily for technical and scientific applications. ... In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ... silica glass is used to make the cores of fibre optic cables. ... General Name, symbol, number titanium, Ti, 22 Chemical series transition metals Group, period, block 4, 4, d Appearance silvery metallic Standard atomic weight 47. ... Germanium dioxide, also called germanium oxide and germania, is an inorganic compound, an oxide of germanium. ...


The erbium-doped fiber amplifier, which reduced the cost of long-distance fiber systems by reducing or even in many cases eliminating the need for optical-electrical-optical repeaters, was co-developed by teams led by David Payne of the University of Southampton, and Emmanuel Desurvire at Bell Laboratories in 1986. The more robust optical fiber commonly used today utilizes glass for both core and sheath and is therefore less prone to aging processes. It was invented by Gerhard Bernsee in 1973 by Schott Glass in Germany.[1] In telecommunication, an optical amplifier is a device that amplifies an optical signal directly, without the need to convert it to an electrical signal, or amplify it electrically, and reconvert it to an optical signal. ... This article does not cite any references or sources. ... The University of Southampton is a university situated in the city of Southampton, on the south coast of Great Britain. ... Bell Telephone Laboratories or Bell Labs was originally the research and development arm of the United States Bell System, and was the premier corporate facility of its type, developing a range of revolutionary technologies from telephone switches to specialized coverings for telephone cables, to the transistor. ... Schott Glass AG is a manufacturer of high-quality industrial glass products, such as fiber-optics and components used in flat panel displays. ...


In 1991, the emerging field of photonic crystals led to the development of photonic crystal fiber (Science (2003), vol 299, page 358), which guides light by means of diffraction from a periodic structure, rather than total internal reflection. The first photonic crystal fibers became commercially available in 1996.[2] Photonic crystal fibers can be designed to carry higher power than conventional fiber, and their wavelength dependent properties can be manipulated to improve their performance in certain applications. The opal in this bracelet contains a natural periodic microstructure responsible for its iridescent color. ... Photonic-crystal fiber (PCF), also spelled fibre, is a new class of optical fiber based on the properties of photonic crystals. ...


Applications

Optical fiber communication

Main article: Fiber-optic communication

Optical fiber can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables. It is especially advantageous for long-distance communications, because light propagates through the fiber with little attenuation compared to electrical cables. This allows long distances to be spanned with few repeaters. Additionally, the light signals propagating in the fiber can be modulated at rates as high as 40 Gb/s [3], and each fiber can carry many independent channels, each by a different wavelength of light (wavelength-division multiplexing). Over short distances, such as networking within a building, fiber saves space in cable ducts because a single fiber can carry much more data than a single electrical cable. Fiber is also immune to electrical interference, which prevents cross-talk between signals in different cables and pickup of environmental noise. Also, wiretapping is more difficult compared to electrical connections, and there are concentric dual core fibers that are said to be tap-proof. Because they are non-electrical, fiber cables can bridge very high electrical potential differences and can be used in environments where explosive fumes are present, without danger of ignition. Fiber-optic communication is a method of transmitting information from one place to another by sending light through an optical fiber. ... A computer network is an interconnection of a group of computers. ... A repeater used in a fiber optic communications system regenerates an optical signal by converting it to an electrical signal, processing that electrical signal and then retransmitting an optical signal. ... A gigabit is a unit of information or computer storage, abbreviated Gbit or sometimes Gb. ... In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes multiple optical carrier signals on a single optical fiber by using different wavelengths (colours) of laser light to carry different signals. ... Telephone tapping or Wire tapping/ Wiretapping (in US) describes the monitoring of telephone conversations by a third party, often by covert means. ...


Although fibers can be made out of transparent plastic, glass, or a combination of the two, the fibers used in long-distance telecommunications applications are always glass, because of the lower optical attenuation. Both multi-mode and single-mode fibers are used in communications, with multi-mode fiber used mostly for short distances (up to 500 m), and single-mode fiber used for longer distance links. Because of the tighter tolerances required to couple light into and between single-mode fibers (core diameter about 10 micrometers), single-mode transmitters, receivers, amplifiers and other components are generally more expensive than multi-mode components. Plastic optical fiber (POF) is an optical fiber which is made out of plastic. ... All-silica fiber, also called all-glass fiber or silica-silica fiber, is an optical fiber composed of silica-glass core and cladding. ... In telecommunication, a plastic-clad silica fiber (PCS) is an optical fiber that has a silica-based core and a plastic cladding. ... This article is about Physics. ...


Fiber optic sensors

Optical fibers can be used as sensors to measure strain, temperature, pressure and other parameters. The small size and the fact that no electrical power is needed at the remote location gives the fiber optic sensor an advantage over a conventional electrical sensor in certain applications.


Optical fibers are used as hydrophones for seismic or SONAR applications. Hydrophone systems with more than 100 sensors per fiber cable have been developed. Hydrophone sensor systems are used by the oil industry as well as a few countries' navies. Both bottom mounted hydrophone arrays and towed streamer systems are in use. The German company Sennheiser developed a microphone working with a laser and optical fibers[4]. A hydrophone is a sound-to-electricity transducer for use in water or other liquids, analogous to a microphone for air. ... This article is about underwater sound propagation. ... Sennheiser electronic GmbH & Co. ... This article or section does not cite its references or sources. ... For other uses, see Laser (disambiguation). ...


Optical fiber sensors for temperature and pressure have been developed for downhole measurement in oil wells. The fiber optic sensor is well suited for this environment as it is functioning at temperatures too high for semiconductor sensors (Distributed Temperature Sensing). Distributed temperature sensing systems (DTS) are optoelectronic devices which measure temperatures by means of optical fibres functioning as linear sensors. ...


Another use of the optical fiber as a sensor is the optical gyroscope which is in use in the Boeing 767 and in some car models (for navigation purposes) and the use in Hydrogen microsensors. A fibre optic gyroscope (FOG) contains a coil with a long (up to 5 km) wound optical fiber (3). ... American Airlines Boeing 767-300 at Gatwick Airport, England. ... A hydrogen microsensor is a small-scale device that detects the presence of hydrogen. ...


Fiber-optic sensors have been developed to measure co-located temperature and strain simultaneously with very high accuracy[5]. This is particularly useful when acquiring information from small complex structures.


Other uses of optical fibers

A frisbee illuminated by fiber optics
A frisbee illuminated by fiber optics

Fibers are widely used in illumination 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 are used to route sunlight from the roof to other parts of the building (see non-imaging optics). Optical fiber illumination is also used for decorative applications, including signs, art, and artificial Christmas trees. Swarovski boutiques use optical fibers to illuminate their crystal showcases from many different angles while only employing one light source. Optical fiber is an intrinsic part of the light-transmitting concrete building product, LiTraCon. Image File history File links Flashflight_red. ... Image File history File links Flashflight_red. ... A Wham-O Professional Frisbee For the amusement ride, see Frisbee (ride). ... Light tubes or light pipes are used for transporting or distributing natural or artificial light. ... Non-imaging optics is the branch of optics concerned with the optimal transfer of light between a source and a target. ... Look up Decoration in Wiktionary, the free dictionary. ... Multiple logos on the Virgin Megastore in San Francisco, California . Los Angeles famous Hollywood sign, now a symbol the entertainment industry, originally said Hollywoodland, and advertised a real estate development. ... This article is about the philosophical concept of Art. ... For other uses, see Christmas tree (disambiguation). ... Swarovski crystal beads Swarovski Wattens Der Firmengründer Daniel Swarovski (1862 † 1956) Swarovskistraße Wattens September 2007 Swarovski is the luxury brand name for the range of precision-cut lead crystal glass products produced by companies owned by Swarovski AG of Feldmeilen, near Zürich, Switzerland. ... LiTraCon (light transmitting concrete) is a translucent concrete product. ...

A fiber-optic Christmas Tree
A fiber-optic Christmas Tree

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 (endoscopy). Industrial endoscopes (see fiberscope or borescope) are used for inspecting anything hard to reach, such as jet engine interiors. Image File history File links F-O-Xmastree. ... Image File history File links F-O-Xmastree. ... Endoscopic images of a duodenal ulcer A flexible endoscope. ... A low quality fiberscope observing the inside of an antique clock mechanism. ... A borescope is a rigid tube with an eyepiece on one end, an objective lens on the other linked together by a relay optical system in between. ...


An optical fiber doped with certain rare-earth elements such as erbium can be used as the gain medium of a laser or optical amplifier. 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. 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. A dopant, also called doping agent and dope, is an impurity element added to a semiconductor lattice in low concentrations in order to alter the optical/electrical properties of the semiconductor. ... Rare earth ore Rare earth elements and rare earth metals are trivial names sometimes applied to a collection of sixteen chemical elements in the periodic table, namely scandium, yttrium, and fourteen of the fifteen lanthanides (excluding promethium), which naturally occur on the Earth. ... General Name, Symbol, Number erbium, Er, 68 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Standard atomic weight 167. ... A laser system generally consists of three important parts: An energy source (usually referred to as the pump or pump source); A gain medium or laser medium; A mirror, or system of mirrors, forming an optical resonator. ... A fiber laser or fibre laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium or ytterbium. ... An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. ... Generally, amplification is a basic process sometimes seen in nature, and often used in processes which involve a signal which must be made stronger. ... Optical pumping is a process in which light is used to raise (or pump) electrons from a lower energy level in an atom or molecule to a higher one. ... In optics, stimulated emission is the process by which, when perturbed by a photon, matter may lose energy resulting in the creation of another photon. ...


Optical fibers doped with a wavelength shifter are used to collect scintillation light in physics experiments. A wavelength shifter is a photofluorescent material that absorbs higher frequency photons and emits lower frequency photons. ... A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ...


Optical fiber can be used to supply a low level of power (around one watt) to electronics situated in a difficult electrical environment. Examples of this are electronics in high-powered antenna elements and measurement devices used in high voltage transmission equipment.


Optical fibers are also used in fiber optic gyroscopes, and other interferometry instruments. A ring laser gyroscope uses interference of laser light within a bulk optic ring to detect changes in orientation and spin. ... It has been suggested that Optical interferometry be merged into this article or section. ...


Principle of operation

An optical fiber is a cylindrical dielectric waveguide that transmits light along its axis, by the process of total internal reflection. The fiber consists of a core surrounded by a cladding layer. To confine the optical signal in the core, the refractive index of the core must be greater than that of the cladding. The boundary between the core and cladding may either be abrupt, in step-index fiber, or gradual, in graded-index fiber. A dielectric is a nonconducting substance, i. ... In electromagnetics and communications engineering, a waveguide is defined as any physical structure that guides electromagnetic waves. ... Critical angle redirects here. ... The term cladding can have a number of meanings: Regarding optical fiber in telecommunication, cladding is one or more layers of material of lower refractive index, in intimate contact with a core material of higher refractive index. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... For an optical fiber, a step-index profile is refractive index profile characterized by a uniform refractive index within the core and a sharp decrease in refractive index at the core-cladding interface. ... In telecommunication, a graded-index fiber is an optical fiber with a core having a refractive index that decreases with increasing radial distance from the fiber axis. ...


Multimode fiber

The propagation of light through a multi-mode optical fiber.
The propagation of light through a multi-mode optical fiber.

Fiber with large (greater than 10 μm) core diameter may be analyzed by geometric optics. Such fiber is called multimode fiber, from the electromagnetic analysis (see below). In a step-index multimode fiber, rays of light are guided along the fiber core by total internal reflection. Rays that meet the core-cladding boundary at a high angle (measured relative to a line normal to the boundary), greater than the critical angle for this boundary, are completely reflected. The critical angle (minimum angle for total internal reflection) is determined by the difference in index of refraction between the core and cladding materials. Rays that meet the boundary at a low angle are refracted from the core into the cladding, and do not convey light and hence information along the fiber. The critical angle determines the acceptance angle of the fiber, often reported as a numerical aperture. A high numerical aperture allows light to propagate down the fiber in rays both close to the axis and at various angles, allowing efficient coupling of light into the fiber. However, this high numerical aperture increases the amount of dispersion as rays at different angles have different path lengths and therefore take different times to traverse the fiber. A low numerical aperture may therefore be desirable. Image File history File links Diagram showing how light is guided through an optical fibre Incident rays which fall within the acceptance cone of the fiber are transmitted, whereas those which fall outside of the acceptance cone are lost in the cladding. ... Image File history File links Diagram showing how light is guided through an optical fibre Incident rays which fall within the acceptance cone of the fiber are transmitted, whereas those which fall outside of the acceptance cone are lost in the cladding. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ... See also list of optical topics. ... See Single-mode optical fiber ... In optics, a ray is an idealized narrow beam of light. ... A surface normal, or just normal to a flat surface is a three-dimensional vector which is perpendicular to that surface. ... In geometric optics, at a refractive boundary, the critical angle is the angle of incidence above which total internal reflection occurs. ... CORE may refer to: The Congress of Racial Equality in the USA. The Coordinated Online Register of Electors in the United Kingdom. ... In optical fibers the acceptance angle θ is the half-angle of the cone within which incident light is totally internally reflected by the fiber core. ... Numerical aperture is a technical term of multiple uses: Numerical aperture of optical telecommunication fiber Numerical aperture in microscopy This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Dispersion of a light beam in a prism. ... In optics and telecommunication, the term optical path length has the following meanings: In a medium of constant refractive index, n , the product of the geometric distance and the refractive index. ...

Optical fiber types.
Optical fiber types.

In graded-index fiber, the index of refraction in the core decreases continuously between the axis and the cladding. This causes light rays to bend smoothly as they approach the cladding, rather than reflecting abruptly from the core-cladding boundary. The resulting curved paths reduce multi-path dispersion because high angle rays pass more through the lower-index periphery of the core, rather than the high-index center. The index profile is chosen to minimize the difference in axial propagation speeds of the various rays in the fiber. This ideal index profile is very close to a parabolic relationship between the index and the distance from the axis. Image File history File links Optical_fiber_types. ... Image File history File links Optical_fiber_types. ... A parabola A graph showing the reflective property, the directrix (light blue), and the lines connecting the focus and directrix to the parabola (blue) In mathematics, the parabola (from the Greek: παραβολή) (IPA pronunciation: ) is a conic section generated by the intersection of a right circular conical surface and a plane...

Singlemode fiber

A typical single-mode optical fiber, showing diameters of the component layers.
A typical single-mode optical fiber, showing diameters of the component layers.

Fiber with a core diameter less than about ten times the wavelength of the propagating light cannot be modeled using geometric optics. Instead, it must be analyzed as an electromagnetic structure, by solution of Maxwell's equations as reduced to the electromagnetic wave equation. The electromagnetic analysis may also be required to understand behaviors such as speckle that occur when coherent light propagates in multi-mode fiber. As an optical waveguide, the fiber supports one or more confined transverse modes by which light can propagate along the fiber. Fiber supporting only one mode is called single-mode or mono-mode fiber. The behavior of larger-core multimode fiber can also be modeled using the wave equation, which shows that such fiber supports more than one mode of propagation (hence the name). The results of such modeling of multi-mode fiber approximately agree with the predictions of geometric optics, if the fiber core is large enough to support more than a few modes. Image File history File links Singlemode_fibre_structure. ... Image File history File links Singlemode_fibre_structure. ... For other uses, see Wavelength (disambiguation). ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... For thermodynamic relations, see Maxwell relations. ... Lasers used for visual effects during a musical performance. ... Laser speckle on a digital camera image from a green laser pointer. ... Coherence is the property of wave-like states that enables them to exhibit interference. ... A transverse mode of a beam of electromagnetic radiation is a particular intensity pattern of radiation measured in a plane perpendicular (i. ... In fiber optics, a single-mode optical fiber is an optical fiber in which only the lowest order bound mode can propagate at the wavelength of interest. ...


The waveguide analysis shows that the light energy in the fiber is not completely confined in the core. Instead, especially in single-mode fibers, a significant fraction of the energy in the bound mode travels in the cladding as an evanescent wave. An evanescent wave is an electromagnetic wave that decays exponentially with distance. ...


The most common type of single-mode fiber has a core diameter of 8 to 10 μm and is designed for use in the near infrared. The mode structure depends on the wavelength of the light used, so that this fiber actually supports a small number of additional modes at visible wavelengths. Multi-mode fiber, by comparison, is manufactured with core diameters as small as 50 micrometres and as large as hundreds of micrometres. Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ...


Special-purpose fiber

Some special-purpose optical fiber is constructed with a non-cylindrical core and/or cladding layer, usually with an elliptical or rectangular cross-section. These include polarization-maintaining fiber and fiber designed to suppress whispering gallery mode propagation. In telecommunication, a polarization-maintaining optical fiber (PM) is an optical fiber in which the polarization planes of lightwaves launched into the fiber are maintained during propagation with little or no cross-coupling of optical power between the polarization modes. ...


Photonic crystal fiber is made with a regular pattern of index variation (often in the form of cylindrical holes that run along the length of the fiber). Such fiber uses diffraction effects instead of or in addition to total internal reflection, to confine light to the fiber's core. The properties of the fiber can be tailored to a wide variety of applications. Photonic-crystal fiber (PCF), also spelled fibre, is a new class of optical fiber based on the properties of photonic crystals. ... The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ...


Manufacturing

Materials

Glass optical fibers are almost always made from silica, but some other materials, such as fluorozirconate, fluoroaluminate, and chalcogenide glasses, are used for longer-wavelength infrared applications. Like other glasses, these glasses have a refractive index of about 1.5. Typically the difference between core and cladding is less than one percent. The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... A Chalcogenide glass is a glass containing a chalcogenide element (sulphur, selenium or tellurium) as a substantial constituent. ...


Plastic optical fibers (POF) are commonly step-index multimode fibers with a core diameter of 0.5 mm or larger. POF typically have higher attenuation co-efficients than glass fibers, 1 dB/m or higher, and this high attenuation limits the range of POF-based systems. Plastic optical fiber (POF) is an optical fiber which is made out of plastic. ...


Process

Standard optical fibers are made by first constructing a large-diameter preform, with a carefully controlled refractive index profile, and then pulling the preform to form the long, thin optical fiber. The preform is commonly made by three chemical vapor deposition methods: inside vapor deposition, outside vapor deposition, and vapor axial deposition.[6] DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ...


With inside vapor deposition, a hollow glass tube approximately 40 cm in length known as a "preform" is placed horizontally and rotated slowly on a lathe, and gases such as silicon tetrachloride (SiCl4) or germanium tetrachloride (GeCl4) are injected with oxygen in the end of the tube. The gases are then heated by means of an external hydrogen burner, bringing the temperature of the gas up to 1900 kelvins, where the tetrachlorides react with oxygen to produce silica or germania (germanium oxide) particles. When the reaction conditions are chosen to allow this reaction to occur in the gas phase throughout the tube volume, in contrast to earlier techniques where the reaction occurred only on the glass surface, this technique is called modified chemical vapor deposition. Silicon tetrachloride (SiCl4) is a colourless volatile liquid compound of silicon and chlorine. ... Flash point None R/S statement R: ? S: ? RTECS number LY5220000 Related compounds Other anions  ? Other cations  ? Related ?  ? Related compounds  ? Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references Germanium tetrachloride is a colourless liquid primary used... This article is about the chemical element and its most stable form, or dioxygen. ... For other uses, see Kelvin (disambiguation). ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Germanium dioxide, also called germanium oxide and germania, is an inorganic compound, an oxide of germanium. ...


The oxide particles then agglomerate to form large particle chains, which subsequently deposit on the walls of the tube as soot. The deposition is due to the large difference in temperature between the gas core and the wall causing the gas to push the particles outwards (this is known as thermophoresis). The torch is then traversed up and down the length of the tube to deposit the material evenly. After the torch has reached the end of the tube, it is then brought back to the beginning of the tube and the deposited particles are then melted to form a solid layer. This process is repeated until a sufficient amount of material has been deposited. For each layer the composition can be modified by varying the gas composition, resulting in precise control of the finished fiber's optical properties. This article or section does not cite its references or sources. ...


In outside vapor deposition or vapor axial deposition, the glass is formed by flame hydrolysis, a reaction in which silicon tetrachloride and germanium tetrachloride are oxidized by reaction with water (H2O) in an oxyhydrogen flame. In outside vapor deposition the glass is deposited onto a solid rod, which is removed before further processing. In vapor axial deposition, a short seed rod is used, and a porous preform, whose length is not limited by the size of the source rod, is built up on its end. The porous preform is consolidated into a transparent, solid preform by heating to about 1800 kelvins. An oxyhydrogen flame is the flame attending the combustion of hydrogen and oxygen, and is characterized by a very high temperature. ...


The preform, however constructed, is then placed in a device known as a drawing tower, where the preform tip is heated and the optic fiber is pulled out as a string. By measuring the resultant fiber width, the tension on the fiber can be controlled to maintain the fiber thickness.


Practical issues

Optical fiber cables

Main article: Optical fiber cable

In practical fibers, the cladding is usually coated with a tough resin buffer layer, which may be further surrounded by a jacket layer, usually plastic. These layers add strength to the fiber but do not contribute to its optical wave guide properties. Rigid fiber assemblies sometimes put light-absorbing ("dark") glass between the fibers, to prevent light that leaks out of one fiber from entering another. This reduces cross-talk between the fibers, or reduces flare in fiber bundle imaging applications.[7][8] This article does not cite any references or sources. ... In a fiber optic cable, a buffer is one type of component used to encapsulate one or more optical fibers for the purpose of providing such functions as mechanical isolation, protection from physical damage and fiber identification. ... Cross-Talk is the analogue or digital interference caused by two tracks of information placed too close together for the reading mechanism to discretely discern one entirely from the other. ... Photograph of NASA lunar lander containing lens flare. ...


Modern cables come in a wide variety of sheathings and armor, designed for applications such as direct burial in trenches, dual use as power lines [3], installation in conduit, lashing to aerial telephone poles, submarine installation, or insertion in paved streets. In recent years the cost of small fiber-count pole-mounted cables has greatly decreased due to the high Japanese and South Korean demand for fiber to the home (FTTH) installations. Fiber to the Home (FTTH) is a technology that allows Telephone, Cable TV and High Speed Internet to be accessed via one fiber cable. ...


Traditional fiber's loss increases greatly if the fiber is bent with a radius smaller than around 30 mm. "Bendable fibers", targeted towards easier installation in home environments, have been standardised as ITU-T G.657. This type of fiber can be bent with a radius as low as 7.5 mm without adverse impact. Even more bendable fibers have been developed.[9] Bendable fiber may also be resistant to fiber hacking, in which the signal in a fiber is surreptitiously monitored by bending the fiber and detecting the leakage.[10]


Termination and splicing

ST fiber connector on multimode fiber
ST fiber connector on multimode fiber

Optical fibers are connected to terminal equipment by optical fiber connectors. These connectors are usually of a standard type such as FC, SC, ST, LC, or MTRJ. Image File history File linksMetadata Download high-resolution version (1942x1187, 498 KB) ST optical fiber connector. ... Image File history File linksMetadata Download high-resolution version (1942x1187, 498 KB) ST optical fiber connector. ... An optical fiber connector constitutes a fiber-to-fiber interconnection and aligns the fiber core of two optical fibers. ...


Optical fibers may be connected to each other by connectors or by splicing, that is, joining two fibers together to form a continuous optical waveguide. The generally accepted splicing method is arc fusion splicing, which melts the fiber ends together with an electric arc. For quicker fastening jobs, a "mechanical splice" is used. A 3000 volt electricity arc between two nails Electricity arcs between the power rail and electrical pickup shoe on a London Underground train An electric arc can melt calcium oxide An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current...


Fusion splicing is done with a specialized instrument that typically operates as follows: The two cable ends are fastened inside a splice enclosure that will protect the splices, and the fiber ends are stripped of their protective polymer coating (as well as the more sturdy outer jacket, if present). The ends are cleaved (cut) with a precision cleaver to make them perpendicular, and are placed into special holders in the splicer. The splice is usually inspected via a magnified viewing screen to check the cleaves before and after the splice. The splicer uses small motors to align the end faces together, and emits a small spark between electrodes at the gap to burn off dust and moisture. Then the splicer generates a larger spark that raises the temperature above the melting point of the glass, fusing the ends together permanently. The location and energy of the spark is carefully controlled so that the molten core and cladding don't mix, and this minimizes optical loss. A splice loss estimate is measured by the splicer, by directing light through the cladding on one side and measuring the light leaking from the cladding on the other side. A splice loss under 0.1 dB is typical. The complexity of this process makes fiber splicing much more difficult than splicing copper wire. The melting point of a solid is the temperature range at which it changes state from solid to liquid. ...


Mechanical fiber splices are designed to be quicker and easier to install, but there is still the need for stripping, careful cleaning and precision cleaving. The fiber ends are aligned and held together by a precision-made sleeve, often using a clear index-matching gel that enhances the transmission of light across the joint. Such joints typically have higher optical loss and are less robust than fusion splices, especially if the gel is used. All splicing techniques involve the use of an enclosure into which the splice is placed for protection afterward.


Fibers are terminated in connectors so that the fiber end is held at the end face precisely and securely. A fiber-optic connector is basically a rigid cylindrical barrel surrounded by a sleeve that holds the barrel in its mating socket. It can be push and click, turn and latch, or threaded. A typical connector is installed by preparing the fiber end and inserting it into the rear of the connector body. Quick-set adhesive is usually used so the fiber is held securely, and a strain relief is secured to the rear. Once the adhesive has set, the fiber's end is polished to a mirror finish. Various polish profiles are used, depending on the type of fiber and the application. For singlemode fiber, the fiber ends are typically polished with a slight curvature, such that when the connectors are mated the fibers touch only at their cores. This is known as a "physical contact" (PC) polish. The curved surface may be polished at an angle, to make an "angled physical contact" (APC) connection. Such connections have higher loss than PC connections, but greatly reduced back reflection, because light that reflects from the angled surface leaks out of the fiber core; the resulting loss in signal strength is known as gap loss. APC fiber ends have low back reflection even when disconnected. Gap loss in action Gap loss is a type of signal strength loss that occurs in fiber optic transmission when the signal is transferred from one section of fiber or cable to another. ...


Free-space coupling

It often becomes necessary to align an optical fiber with another optical fiber or an optical device such as a light-emitting diode, a laser diode, or an optoelectronic device such as a modulator. This can involve either carefully aligning the fiber and placing it in contact with the device to which it is to couple, or can use a lens to allow coupling over an air gap. In some cases the end of the fiber is polished into a curved form that is designed to allow it to act as a lens. “LED” redirects here. ... A packaged laser diode with penny for scale. ... For the musical use of modulation, see modulation (music). ... This article is about the optical device. ...


In a laboratory environment, the fiber end is usually aligned to the device or other fiber with a fiber launch system that uses a microscope objective lens to focus the light down to a fine point. A precision translation stage (micro-positioning table) is used to move the lens, fiber, or device to allow the coupling efficiency to be optimized. Several objective lenses on a microscope. ...


Fiber fuse

At high optical intensities, above 2 megawatts per square centimetre, when a fiber is subjected to a shock or is otherwise suddenly damaged, a fiber fuse can occur. The reflection from the damage vaporizes the fiber immediately before the break, and this new defect remains reflective so that the damage propagates back toward the transmitter at 1–3 meters per second.[11],[12],[13] The open fiber control system, which ensures laser eye safety in the event of a broken fiber, can also effectively halt propagation of the fiber fuse.[14] In situations, such as undersea cables, where high power levels might be used without the need for open fiber control, a "fiber fuse" protection device at the transmitter can break the circuit to prevent any damage. For other uses, see Watt (disambiguation). ... Open fiber control is a protocol to ensure that a both ends of a fiber optic cable are connected before laser signals are transmitted in order to protect people from eye damage. ... A typical laser warning symbol. ...


See also

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Image File history File links Nuvola_apps_ksim. ... Gradient index optics is the branch of optics covering optical effects produced by a gradual variation of the refractive index of a material. ... Optical communication is any form of telecommunication that uses light as the transmission medium. ... An optical fiber connector constitutes a fiber-to-fiber interconnection and aligns the fiber core of two optical fibers. ... An optical fiber connector constitutes a fiber-to-fiber interconnection and aligns the fiber core of two optical fibers. ... An optical fiber connector constitutes a fiber-to-fiber interconnection and aligns the fiber core of two optical fibers. ... A fiber connector type. ... A cross-section of a submarine communications cable. ... Cable jetting is a technique to install cables in ducts[1]. It is commonly used to install cables with optical fibers in underground polyethylene ducts and is an alternative to pulling. ... A fiber Bragg grating is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. ... Leaky mode: In an optical fiber or other form of waveguide, a mode having a field that decays monotonically for a finite distance in the transverse direction but becomes oscillatory everywhere beyond that finite distance. ... Front view of SFP module (LC connector). ... The XENPAK Multisource Agreement (MSA), instigated by Agilent Technologies and Agere Systems, defines a fiber-optic transceiver module which conforms to the 10 Gigabit Ethernet (10 GbE) standard as laid down by the IEEE 802. ...

Notes

  1. ^ a b Bates, Regis J (2001). Optical Switching and Networking Handbook. New York: McGraw-Hill, p10. ISBN 007137356X. 
  2. ^ Hecht, Jeff (1999). City of Light, The Story of Fiber Optics. New York: Oxford University Press, p114. ISBN 0195108183. 
  3. ^ Ramachandran (2001), "Higher-order-mode dispersion compensation: enabler for long distance WDM at 40 Gb/sec", Proceedings of the SPIE 4532: 220-226
  4. ^ TP: Der Glasfaser-Schallwandler. Retrieved on December 4, 2005.
  5. ^ Title: Dual temperature and strain sensor using a combined fiber Bragg grating and fluorescence intensity ratio technique in Er3+-doped fiber.
  6. ^ Gowar, John (1993). Optical Communication Systems, 2d ed., Hempstead, UK: Prentice-Hall, p209. ISBN 0136387276. 
  7. ^ Light collection and propagation. National Instruments' Developer Zone. Retrieved on 2007-03-19.
  8. ^ Hecht, Jeff (2002). Understanding Fiber Optics, 4th ed., Prentice Hall. ISBN 0-13-027828-9. 
  9. ^ Corning, Inc. (2007-07-23). "Corning announces breakthrough optical fiber technology". Press release. Retrieved on 2007-12-09.
  10. ^ Olzak, Tom (2007-05-03). Protect your network against fiber hacks. Techrepublic. CNET. Retrieved on 2007-12-10.
  11. ^ The Risks Digest Volume 12: Issue 44. Retrieved on December 4, 2005.
  12. ^ Optics Letters. Retrieved on December 4, 2005.
  13. ^ Photonics Spectra. Retrieved on December 4, 2005.
  14. ^ Evaluation of High-power Endurance in Optical Fiber Links. Retrieved on December 4, 2005.

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References

  • Gambling, W. A., "The Rise and Rise of Optical Fibers", IEEE Journal on Selected Topics in Quantum Electronics, Vol. 6, No. 6, pp. 1084-1093, Nov./Dec. 2000.
  • Hecht, Jeff, Understanding Fiber Optics, 4th ed., Prentice-Hall, Upper Saddle River, NJ, USA 2002 (ISBN 0-13-027828-9).
  • Mirabito, Michael M.A; and Morgenstern, Barbara L., The New Communications Technologies: Applications, Policy, and Impact, 5th. Edition. Focal Press, 2004. (ISBN 0-24-080586-0).
  • Nagel S. R., MacChesney J. B., Walker K. L., "An Overview of the Modified Chemical Vapor Deposition (MCVD) Process and Performance", IEEE Journal of Quantum Electronics, Vol. QE-18, No. 4, p. 459, April 1982.
  • Ramaswami, R., Sivarajan, K. N., Optical Networks: A Practical Perspective, Morgan Kaufmann Publishers, San Francisco, 1998 (ISBN 1-55860-445-6).

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  Results from FactBites:
 
Optical fiber - Wikipedia, the free encyclopedia (2012 words)
By the waveguide analysis, it is seen that the light energy in the fiber is not completely confined in the core, but, especially in single-mode fibers, a significant fraction of the energy in the bound mode travels in the cladding as an evanescent wave.
Fibers are generally used in pairs, with one fiber of the pair carrying a signal in each direction, however bidirectional communications is possible over one strand by using two different wavelengths (colors) and appropriate coupling/splitting devices.
Fibers can be used as light guides in medical and other applications where bright light needs to be brought to bear on a target without a clear line-of-sight path.
Introduction to Fiber Optics Part 1 (including video transmission for a/v) (717 words)
Fiber optic cable is similar to electrical cable in its construction, but provides special protection for the optical fiber within.
Fiber optic cables are virtually unaffected by outdoor atmospheric conditions, allowing them to be lashed directly to telephone poles or existing electrical cables without concern for extraneous signal pickup.
Fiber optic cable is ideal for secure communications systems because it is very difficult to tap but very easy to monitor.
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