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Encyclopedia > Optical fiber communications

Fiber-optic communication is a method of transmitting information from one place to another by sending light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information. First developed in the 1970s, fiber-optic communication systems have revolutionized the telecommunications industry and played a major role in the advent of the Information Age. Because of its advantages over electrical transmission, the use of optical fiber has largely replaced copper wire communications. It has been suggested that this article or section be merged with Electromagnetic radiation. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length by confining as much light as possible in a propagating form. ... It has been suggested that this article or section be merged with light. ... This article or section does not adequately cite its references or sources. ... In telecommunications, modulation is the process of varying a periodic waveform, i. ... Telecommunication involves the transmission of signals over a distance for the purpose of communication. ... It has been suggested that Digital Age be merged into this article or section. ... Fiber-optic communication is a method of transmitting information from one place to another by sending light through an optical fiber. ...


The process of communicating using fiber-optics involves the following basic steps:

  • Creating the optical signal using a transmitter
  • Relaying the signal along the fiber, ensuring that the signal does not become too distorted or weak
  • Receiving the optical signal and converting it into an electrical signal

Contents

Fiber-optic communication is a method of transmitting information from one place to another by sending light through an optical fiber. ... Fiber-optic communication is a method of transmitting information from one place to another by sending light through an optical fiber. ... Fiber-optic communication is a method of transmitting information from one place to another by sending light through an optical fiber. ...

Applications

Fiber-optic cable is used by many telecommunications companies to transmit telephone signals, internet communication, and cable television signals, sometimes all on the same optical fiber. Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length by confining as much light as possible in a propagating form. ...


Due to much lower attenuation and interference, optical fiber has large advantages over existing copper wire in long-distance and high-demand applications. However, infrastructure development within cities was relatively difficult and time-consuming, and fiber-optic systems were complex and expensive to install and operate. Due to these difficulties, fiber-optic communication systems have primarily been installed in long-distance applications, where they can be used to their full transmission capacity, offsetting the increased cost. Since the year 2000, the prices for fiber-optic communications have dropped considerably. The price for rolling out fiber to the home has currently become more cost-effective than that of rolling out a copper based network. Prices have dropped to $850 per subscriber in the US and lower in countries like The Netherlands, where digging costs are low. Attenuation is the reduction in amplitude and intensity of a signal with respect to distance traveled through a medium. ... Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ...


Since 1990, when optical-amplification systems became commercially available, the telecommunications industry has laid a vast network of intercity and transoceanic fiber communication lines. By 2002, an intercontinental network of 250,000 km of submarine communications cable with a capacity of 2.56 Tb/s was completed, and although specific network capacities are privileged information, telecommunications investment reports indicate that network capacity has increased dramatically since 2002. An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. ... The multitude of layers in a submarine communications cable is revealed by its Cross section. ... A terabit 1 terabit = 1012 bits = 1,000,000,000,000 bits (one trillion, long scale: one billion) The terabit is closely related to the tebibit, which is equal to 240 bits. ...


History

The need for reliable long-distance communication systems has existed since antiquity. Over time, the sophistication of these systems has gradually improved, from smoke signals to telegraphs and finally to the first coaxial cable, put into service in 1940. As these communication systems improved, certain fundamental limitations presented themselves. Electrical systems were limited by their small repeater spacing (the distance a signal can propagate before attenuation requires the signal to be amplified), and the bit rate of microwave systems was limited by their carrier frequency. In the second half of the twentieth century, it was realized that an optical carrier of information would have a significant advantage over the existing electrical and microwave carrier signals. A smoke signal is a form of visual communication used over a long distance, developed both in the Americas and in China. ... The electrical telegraph is a telegraph that uses electric signals. ... Coaxial Cable Coaxial cable is an electrical cable consisting of a round conducting wire, surrounded by an insulating spacer, surrounded by a cylindrical conducting sheath, usually surrounded by a final insulating layer (Jacket). ... 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. ... Attenuation is the reduction in amplitude and intensity of a signal with respect to distance traveled through a medium. ... Microwaves are electromagnetic waves with wavelengths longer than those of terahertz (THz) frequencies, but relatively short for radio waves. ... Carrier frequency is the fundamental frequency used in both amplitude modulation and frequency modulation i. ...


However, no coherent light source or suitable transmission medium was available. Then, after the development of lasers in the 1960s solved the first problem, development of high-quality optical fiber was proposed as a solution to the second. Optical fiber was finally developed in 1970 by Corning Glass Works with attenuation low enough for communication purposes (about 20dB/km), and at the same time GaAs semiconductor lasers were developed that were compact and therefore suitable for fiber-optic communication systems. Experiment with a laser (likely an argon type) (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: light amplification by stimulated emission of radiation. ... Corning Glass Works (NYSE: GLW) is a U.S. manufacturer of glass, ceramics and related materials, primarily for technical and scientific applications. ... The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power) relative to a specified or implied reference level. ... km redirects here. ... A packaged laser diode with penny for scale. ...


After a period of intensive research from 1975 to 1980, the first commercial fiber-optic communication system was developed, which operated at a wavelength around 0.8 µm and used GaAs semiconductor lasers. This “first generation” system operated at a bit rate of 45 Mb/s with repeater spacing of up to 10 km. To help compare different orders of magnitude this page lists lengths between 10-6 and 10-5 m (1 µm and 10 µm). ...


The “second generation” of fiber-optic communication was developed for commercial use in the early 1980s, operated at 1.3 µm, and used InGaAsP semiconductor lasers. Although these systems were initially limited by dispersion, in 1981 the single-mode fiber was revealed to greatly improve system performance. By 1987, these systems were operating at bit rates of up to 1.7 Gb/s with repeater spacing up to 50 km. 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. ... A gigabit is a unit of information or computer storage, abbreviated Gbit or sometimes Gb. ...


Third-generation fiber-optic systems operated at 1.55 µm and had loss of about 0.2 dB/km. They achieved this despite earlier difficulties with pulse-spreading at that wavelength using conventional InGaAsP semiconductor lasers. Scientists overcame this difficulty by using dispersion-shifted fibers designed to have minimal dispersion at 1.55 µm or by limiting the laser spectrum to a single longitudinal mode. These developments eventually allowed 3rd generation systems to operate commercially at 2.5 Gb/s with repeater spacing in excess of 100 km. Dispersion of a light beam in a prism. ... Dispersion shifted fiber, specified in ITU-T G.653 and also called DSF, is a type of single-mode optical fiber with an core-clad index profile tailored to shift the zero-dispersion wavelength from the natural 1300 nm in silica-glass fibers to the minimum-loss window at 1550... The first six longitudinal modes of a plane-parallel cavity. ...


The fourth generation of fiber-optic communication systems used optical amplification to reduce the need for repeaters and wavelength-division multiplexing to increase fiber capacity. These two improvements caused a revolution that resulted in the doubling of system capacity every 6 months starting in 1992 until a bit rate of 10 Tb/s was reached by 2001. Recently, bit-rates of up to 14 Tb/s have been reached over a single 160 km line using optical amplifiers. An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. ... This article or section does not cite its references or sources. ... Channel capacity, is the amount of discrete information that can be reliably transmitted over a channel. ... A terabit 1 terabit = 1012 bits = 1,000,000,000,000 bits (one trillion, long scale: one billion) The terabit is closely related to the tebibit, which is equal to 240 bits. ...


The focus of development for the fifth generation of fiber-optic communications is on extending the wavelength range over which a WDM system can operate. The conventional wavelength window, known as the C band, covers the wavelength range 1.53–1.57 µm, and the new “dry fiber” has a low-loss window promising an extension of that range to 1.30 to 1.65 µm. Other developments include the concept of “optical solitons,” pulses that preserve their shape by counteracting the effects of dispersion with the nonlinear effects of the fiber by using pulses of a specific shape. In optics, the term soliton is used to refer any optical field that does not change during propagation because of a delicate balance between nonlinear and linear effects in the medium. ... Nonlinear optics is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization P responds nonlinearly to the electric field E of the light. ...


In the late 1990s through 2000, the fiber optic communication industry became associated with the dot-com bubble. Industry promoters, and research companies such as KMI and RHK predicted vast increases in demand for communications bandwidth due to increased use of the Internet, and commercialization of various bandwidth-intensive consumer services, such as video on demand. Internet protocol data traffic was said to be increasing exponentially, and at a faster rate than integrated circuit complexity had increased under Moore's Law. From the bust of the dot-com bubble through 2006, however, the main trend in the industry has been consolidation of firms and offshoring of manufacturing to reduce costs. The dot-com bubble was a speculative bubble covering roughly 1995–2001 during which stock markets in Western nations saw their value increase rapidly from growth in the new Internet sector and related fields. ... Video on demand (VOD) systems allow users to select and watch video content over a network as part of an interactive television system. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... Growth of transistor counts for Intel processors (dots) and Moores Law (upper line=18 months; lower line=24 months) Moores Law is the empirical observation made in 1965 that the number of transistors on an integrated circuit for minimum component cost doubles every 24 months. ... Consolidation is the act of merging many things into one. ... Offshoring describes the relocation of business processes from one country to another. ...


Technology

Modern fiber-optic communication systems generally include an optical transmitter to convert an electrical signal into an optical signal to send into the optical fiber, a fiber-optic cable routed through underground conduits and buildings, multiple kinds of amplifiers, and an optical receiver to recover the signal as an electrical signal. The information transmitted is typically digital information generated by computers, telephone systems, and cable television companies. Digital communication, as opposed to analogue communication refers to all emerging communications and technologies via a digital platform usually combining text, graphics, sound, and video, utilising computer or mobile technology. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Coaxial cable is often used to transmit cable television into the house. ...


Transmitters

The most commonly used optical transmitters are semiconductor devices such as light-emitting diodes (LEDs) and laser diodes. The difference between LEDs and laser diodes is that LEDs produce incoherent light, while laser diodes produce coherent light. For use in optical communications, semiconductor optical transmitters must be designed to be compact, efficient, and reliable, while operating in an optimal wavelength range, and directly modulated at high frequencies. Led is also the past tense of the verb to lead Blue, green and red LEDs. ... A packaged laser diode with penny for scale. ... Coherence is the property of wave-like states that enables them to exhibit interference. ... Coherence is the property of wave-like states that enables them to exhibit interference. ...


In its simplest form, an LED is a forward-biased p-n junction, emitting light through spontaneous emission, a phenomenon referred to as electroluminescence. The emitted light is incoherent with a relatively wide spectral width of 30-60 nm. LED light transmission is also inefficient, with only about 1% of input power, or about 100 microwatts, eventually converted into “launched power” which has been coupled into the optical fiber. However, due to their relatively simple design, LEDs are very useful for low-cost applications. A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ... Spontaneous emission is the process by which a molecule in an excited state drops to the ground state, resulting in the creation of a photon. ... Animation of LCD, both unlit and with electroluminiscent backlight switched on Electroluminescence (EL) is an optical phenomenon and electrical phenomenon where a material emits light in response to an electric current passed through it, or to a strong electric field. ...


Communications LEDs are most commonly made from gallium arsenide phosphide (GaAsP) or gallium arsenide (GaAs). Because GaAsP LEDs operate at a longer wavelength than GaAs LEDs (1.3 micrometers vs. 0.81-0.87 micrometers), their output spectrum is wider by a factor of about 1.7. The large spectrum width of LEDs causes higher fiber dispersion, considerably limiting their bit rate-distance product (a common measure of usefulness). LEDs are suitable primarily for local-area-network applications with bit rates of 10-100 Mb/s and transmission distances of a few kilometers. LEDs have also been developed that use several quantum wells to emit light at different wavelengths over a broad spectrum, and are currently in use for local-area WDM networks. Gallium arsenide phosphide (GaAsP) is a semiconductor material, an alloy of gallium arsenide and gallium phosphide. ... This article is about the chemical compound. ... Local area network scheme A local area network is a computer network covering a small geographic area, like a home, office, or group of buildings. ... A quantum well is a potential well that confines particles in one dimension, forcing them to occupy a planar region. ... This article or section does not cite its references or sources. ...


A semiconductor laser emits light through stimulated emission rather than spontaneous emission, which results in high output power (~100 mW) as well as other benefits related to the nature of coherent light. The output of a laser is relatively directional, allowing high coupling efficiency (~50%) into single-mode fiber. The narrow spectral width also allows for high bit rates since it reduces the effect of chromatic dispersion. Furthermore, semiconductor lasers can be modulated directly at high frequencies because of short recombination time. 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. ... Dispersion of a light beam in a prism. ... In the solid state physics of semiconductors, carrier generation and recombination are processes by which mobile electrons and electron holes are created and eliminated. ...


Laser diodes are often directly modulated, that is the light output is controlled by a current applied directly to the device. For very high data rates or very long distance links, a laser source may be operated continuous wave, and the light modulated by an external device such as an electroabsorption modulator or Mach-Zehnder interferometer. External modulation increases the achievable link distance by eliminating laser chirp, which broadens the linewidth of directly-modulated lasers, increasing the chromatic dispersion in the fiber. In telecommunications, modulation is the process of varying a periodic waveform, i. ... A continuous wave (CW) is an electromagnetic wave of constant amplitude and frequency. ... The Mach-Zehnder interferometer is used to determine the phase shift caused by a small sample which is to be placed into one of the two beams D and U, respectively, from a coherent light source. ... This article or section does not cite its references or sources. ... The Q factor or quality factor is a measure of the quality of a resonant system. ...


Fiber

Main article: Optical fiber. Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length by confining as much light as possible in a propagating form. ...


Optical fiber consists of a core, cladding, and a protective outer coating, which guide light along the core by total internal reflection. The core, and the higher-refractive-index cladding, are typically made of high-quality silica glass, though they can both be made of plastic as well. An optical fiber can break if bent too sharply. Due to the microscopic precision required to align the fiber cores, connecting two optical fibers, whether done by fusion splicing or mechanical splicing, requires special skills and interconnection technology.[1]. The larger the angle to the normal, the smaller is the fraction of light transmitted, until the angle when total internal reflection occurs. ... 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. ... R-phrases R42 R43 R49 S-phrases S22 S36 S37 S45 S53 Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ...


Two main categories of optical fiber used in fiber optic communications are multi-mode optical fiber and single-mode optical fiber. Multimode fiber has a larger core (≥ 50 microns), allowing less precise, cheaper transmitters and receivers to connect to it as well as cheaper connectors. However, multi-mode fiber introduces multimode distortion which often limits the bandwidth and length of the link. Furthermore, because of its higher dopant content, multimode fiber is usually more expensive and exhibits higher attenuation. Single-mode fiber's smaller core (<10 microns) necessitates more expensive components and interconnection methods, but allows much longer, higher-performance links. Multi-mode optical fiber (multimode fiber or MM fiber) is a type of optical fiber mostly used for communication over shorter distances, e. ... 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. ... 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. ... Multimode distortion is a distortion mechanism occurring in multimode fibers and other waveguides, in which the signal is spread in time because the propagation velocity of the optical signal is not the same for all modes. ... 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. ...


In order to package fiber into a commercially-viable product, it is protectively-coated, typically by using ultraviolet (UV) light-cured acrylate polymers, and assembled into a fiber-optic cable. It can then be laid in the ground, run through a building or deployed aerially in a manner similar to copper cable. Once deployed, such cables require substantially less maintenance than copper cable. [1] The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... 6 or 15cm outside diameter, oil-cooled cables, traversing the Grand Coulee Dam throughout. ...


Amplifiers

Main article: Optical amplifier. An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. ...


The transmission distance of a fiber-optic communication system has traditionally been limited primarily by fiber attenuation and second by fiber distortion. The solution to this has been to use opto-electronic repeaters. These repeaters first convert the signal to an electrical signal then use a transmitter to send the signal again at a higher intensity. Because of their high complexity, especially with modern wavelength-division multiplexed signals, and the fact that they had to be installed about once every 20 km, the cost for these repeaters was very high.


An alternative approach is to use an optical amplifier, which amplifies the optical signal directly without having to convert the signal into the electrical domain. Made by doping a length of fiber with the rare-earth mineral erbium, and pumping it with light from a laser with a shorter wavelength than the communications signal (typically 980 nm), amplifiers have largely replaced repeaters in new installations. In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ... General Name, Symbol, Number erbium, Er, 68 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Atomic mass 167. ... Laser pumping is the act of energy transfer from an external source into the laser gain medium. ... Experiment with a laser (likely an argon type) (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: light amplification by stimulated emission of radiation. ... A nanometre (American spelling: nanometer) is 1. ...


Receivers

The main component of an optical receiver is a photodetector that converts light into electricity through the photoelectric effect. The photodetector is typically a semiconductor-based photodiode, such as a p-n photodiode, a p-i-n photodiode, or an avalanche photodiode. Metal-semiconductor-metal (MSM) photodetectors are also used due to their suitability for circuit integration in regenerators and wavelength-division multiplexers. Photosensors or photodetectors appear in several varieties: Photoresistors or Light Dependant Resistors (LDR) which change resistance when illuminated Photovoltaic cells or solar cells which produce a voltage and supply an electric current when illuminated Photodiodes which can operate in photovoltaic mode or photoconductive mode Phototubes containing a photocathode which emits... A diagram illustrating the emission of photoelectrons from a metal plate, requiring energy gained from an incoming photon to be more than the work function of the material. ... A photodiode Photodiode closeup A photodiode is a semiconductor diode that functions as a photodetector. ... Integrated circuit showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window showing the integrated circuit inside. ...


The optical-electrical converters is typically coupled with a transimpedance amplifier and limiting amplifier to produce a digital signal in the electrical domain from the incoming optical signal, which may be attenuated and distorted by passing through the channel. Further signal processing such as clock recovery from data (CDR) by a phase-locked loop may also be applied before the data is passed on. A transimpedance amplifier is a circuit that performs current to voltage transfomation and is sometimes known simply as a current-to-voltage converter. ... In electronics, a phase-locked loop (PLL) is a closed-loop feedback control system that generates and outputs a signal in relation to the frequency and phase of an input (reference) signal. ...


Wavelength-division multiplexing

Main article: Wavelength-division multiplexing. This article or section does not cite its references or sources. ...


Wavelength-division multiplexing (WDM) is the practice of dividing the wavelength capacity of an optical fiber into multiple channels in order to send more than one signal over the same fiber. This requires a wavelength division multiplexer in the transmitting equipment and a wavelength division demultiplexer (essentially a spectrometer) in the receiving equipment. Arrayed waveguide gratings are commonly used for multiplexing and demultiplexing in WDM. Using WDM technology now commercially available, the bandwidth of a fiber can be divided into as many as 80 channels to support a combined bit rate into the range of terabits per second. Schematic of a 2-to-1 Multiplexer. ... A spectrometer is an optical instrument used to measure properties of light over a specific portion of the electromagnetic spectrum. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... A terabit 1 terabit = 1012 bits = 1,000,000,000,000 bits (one trillion, long scale: one billion) The terabit is closely related to the tebibit, which is equal to 240 bits. ...


Bandwidth-distance product

Because the effect of dispersion increases with the length of the fiber, a fiber transmission system is often characterized by its bandwidth-distance product, often expressed in units of MHz×km. This value is a product of bandwidth and distance because there is a trade off between the bandwidth of the signal and the distance it can be carried. For example, a common multimode fiber with bandwidth-distance product of 500 MHz×km could carry a 500 MHz signal for 1 km or a 1000 MHz signal for 0.5 km. The hertz (symbol: Hz) is the SI unit of frequency. ...


Limitations

Through a combination of advances in dispersion management, wavelength-division multiplexing, and optical amplifiers, modern-day optical fibers can carry information at around 14 Terabits per second over 160 kilometers of fiber [2]. Engineers are always looking at current limitations in order to improve fiber-optic communication, and several of these restrictions are currently being researched: This article or section does not cite its references or sources. ...


Dispersion

For modern glass optical fiber, the maximum transmission distance is limited not by attenuation but by dispersion, or spreading of optical pulses as they travel along the fiber. Dispersion in optical fibers is caused by a variety of factors. Intermodal dispersion, caused by the different axial speeds of different transverse modes, limits the performance of multi-mode fiber. Because single-mode fiber supports only one transverse mode, intermodal dispersion is eliminated. Attenuation is the reduction in amplitude and intensity of a signal with respect to distance traveled through a medium. ... Dispersion of a light beam in a prism. ... Multi-mode optical fiber (multimode fiber or MM fiber) is a type of optical fiber mostly used for communication over shorter distances, e. ...


In single-mode fiber performance is primarily limited by chromatic dispersion (also called group velocity dispersion), which occurs because the index of the glass varies slightly depending on the wavelength of the light, and light from real optical transmitters has nonzero spectral width. Polarization mode dispersion, another source of limitation, occurs because although the single-mode fiber can sustain only one transverse mode, it can carry this mode with two different polarizations, and slight imperfections or distortions in a fiber can alter the propagation velocities for the two polarizations. This phenomenon is called fiber birefringence and can be counteracted by polarization-maintaining optical fiber. Dispersion limits the bandwidth of the fiber because the spreading optical pulse limits the rate that pulses can follow one another on the fiber and still be distinguishable at the receiver. The chromatic dispersion of an optical medium is basically the frequency dependence of the phase velocity and group velocity of light propagating in a medium. ... Dispersion of a light beam in a prism. ... Polarization mode dispersion (PMD) is a form of modal dispersion where two different polarizations of light in a waveguide, which normally travel at the same speed, travel at different speeds due to random imperfections and asymmetries, causing random spreading of optical pulses. ... A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... 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. ...


Attenuation

Fiber attenuation, which necessitates the use of amplification systems, is caused by a combination of material absorption, Rayleigh scattering, Mie scattering, and connection losses. Although material absorption for pure silica is only around 0.03db/km (modern fiber has attenuation around 0.3 db/km), impurities in the original optical fibers caused attenuation of about 1000 db/km. The root causes of the other forms of attenuation are physical stresses to the fiber, microscopic fluctuations in density, and imperfect splicing techniques. Attenuation is the decrease in intensity of electromagnetic radiation due to absorption or scattering of photons. ... In physics, absorption is the process by which the energy of a photon is taken up by another entity, for example, by an atom whose valence electrons make a transition between two electronic energy levels. ... Rayleigh scattering causing a reddened sky at sunset Rayleigh scattering (named after Lord Rayleigh (RAY-lee)) is the scattering of light, or other electromagnetic radiation, by particles much smaller than the wavelength of the light. ... Mie theory, also called Lorenz-Mie theory or Lorenz-Mie-Debye theory, is a complete analytical solution of Maxwells equations for the scattering of electromagnetic radiation by spherical particles (also called Mie scattering). ...


Regeneration

When a communications link must span a larger distance than existing fiber-optic technology is capable of, the signal must be regenerated at intermediate points in the link by repeaters. Repeaters add substantial cost to a communication system, and so system designers attempt to minimize their use. 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. ...


Recent advances in fiber and optical communications technology have reduced signal degradation so far that regeneration of the optical signal is only needed over distances of hundreds of kilometers. This has greatly reduced the cost of optical networking, particularly over undersea spans where the cost and reliability of repeaters is one of the key factors determining the performance of the whole cable system. The main advances contributing to these performance improvements are dispersion management, which seeks to balance the effects of dispersion against non-linearity; and solitons, which use nonlinear effects in the fiber to enable dispersion-free propagation over long distances. In optics, the term soliton is used to refer any optical field that does not change during propagation because of a delicate balance between nonlinear and linear effects in the medium. ...


Last mile

Although fiber-optic systems excel in high-bandwidth applications, optical fiber has been slow to achieve its goal of “fiber to the premises” or to solve the “last mile” problem. However, as bandwidth demand increases, more and more progress to this goal can be observed, for example in Japan where fiber-optic systems are beginning to replace wire-based DSL as a broadband internet source. Fiber to the premises (FTTP) is a form of fiber-optic communication delivery in which an optical fiber is run directly onto the customers premises. ... The last mile is the final leg of delivering connectivity from a communications provider to a customer. ...


Comparison with electrical transmission

The choice between optical fiber and electrical (or "copper") transmission for a particular system is made based on a number of trade-offs. Optical fiber is generally chosen for systems with higher bandwidths or spanning longer distances than electrical cabling can provide. The main benefits of fiber are its exceptionally low loss, allowing long distances between amplifiers or repeaters; and its inherently high data-carrying capacity, such that thousands of electrical links would be required to replace a single high bandwidth fiber. Another benefit of fiber is that even when run alongside each other for long distances, fiber cables experience effectively no crosstalk, in contrast to some types of electrical transmission lines. This article or section does not cite its references or sources. ... In telecommunication, the term crosstalk (XT) has the following meanings: 1. ... A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electromagnetic waves or acoustic waves, as well as electric power transmission. ...


In short distance and relatively low bandwidth applications, electrical transmission is often preferred because of its

  • Lower material cost, where large quantities are not required.
  • Lower cost of transmitters and receivers.
  • Ease of splicing.
  • Capability to carry electrical power as well as signals.

Because of these benefits of electrical transmission, optical communication is not common in short box-to-box, backplane, or chip-to-chip applications; however, optical systems on those scales have been demonstrated in the laboratory. Splice has several meanings: In outdoor recreation (such as sailing or camping) rope splicing involves joining two pieces of rope or wire by weaving the strands of each into the other. ... Transmission lines in Lund, Sweden Electric power, often known as power or electricity, involves the production and delivery of electrical energy in sufficient quantities to operate domestic appliances, office equipment, industrial machinery and provide sufficient energy for both domestic and commercial lighting, heating, cooking and industrial processes. ... A backplane is a circuit board (usually a printed circuit board) that connects several connectors in parallel to each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. ...


In certain situations fiber may be used even for short distance or low bandwidth applications, due to other important features:

  • Immunity to electromagnetic interference, including nuclear electromagnetic pulses (although fiber can be damaged by alpha and beta radiation).
  • High electrical resistance, making it safe to use near high-voltage equipment or between areas with different earth potentials.
  • Lighter weight, important, for example, in aircraft.
  • No sparks, important in flammable or explosive gas environments.
  • Not electromagnetically radiating, and difficult to tap without disrupting the signal, important in high-security environments.
  • Much smaller cable size - important where pathway is limited.

Example of an electromagnetic pulse, in this case caused by the electrical discharge required to fire the Z machine. ... An alpha particle is deflected by a magnetic field Alpha particles (named after the first letter in the Greek alphabet, α) are a highly ionizing form of particle radiation which have low penetration. ... Alpha radiation consists of helium nuclei and is readily stopped by a sheet of paper. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ...

Governing standards

In order for various manufacturers to be able to develop components that function compatibly in fiber optic communication systems, a number of standards have been developed. The International Telecommunications Union publishes several standards related to the characteristics and performance of fibers themselves, including The International Telecommunication Union (ITU) is an international organization established to standardize and regulate international radio and telecommunications. ...

  • ITU-T G.651, "Characteristics of a 50/125 µm multimode graded index optical fibre cable"
  • ITU-T G.652, "Characteristics of a single-mode optical fibre cable"

Other standards, produced by a variety of standards organizations, specify performance criteria for fiber, transmitters, and receivers to be used together in conforming systems. Some of these standards are the following: Standards Organizations are bodies, organizations and institutions that produce, and in some cases measure, standards. ...

TOSLINK is the most common format for digital audio cable using plastic optical fiber to connect digital sources to digital receivers. 10 gigabit Ethernet or 10GbE is the most recent (as of 2006) and fastest of the Ethernet standards. ... In computer networking, fiber-distributed data interface (FDDI) is a standard for data transmission in a local area network that can extend in range up to 200 km (124 miles). ... This article or section does not adequately cite its references or sources. ... Gigabit Ethernet (GbE) is a term describing various technologies for transmitting Ethernet packets at a rate of a gigabit per second, as defined by the IEEE 802. ... HIPPI (HIgh Performance Parallel Interface) is a computer bus for the attachment of high speed storage devices to supercomputers. ... Synchronous Optical Networking, commonly known as SONET, is a standard for communicating digital information over optical fiber. ... Synchronous Optical Networking, commonly known as SONET, is a standard for communicating digital information over optical fiber. ... TOSLINK is a standardized optical fiber connection system. ... Digital audio comprises audio signals stored in a digital format. ... Plastic optical fiber (POF) is an optical fiber which is made out of plastic. ... In radio terminology, a receiver is an electronic circuit that receives a radio signal from an antenna and decodes the signal for use as sound, pictures, navigational-position information, etc. ...


See also

Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length by confining as much light as possible in a propagating form. ... Optical communication is any form of telecommunication that uses light as the transmission medium. ... A bundle of optical fiber. ... In fibre-optic communications, dark fibre or unlit fibre (or fiber) is the name given to individual fibers that have yet to be used within cables that have been already laid. ...

References

  • Encyclopedia of Laser Physics and Technology
  • Fiber-Optic Technologies by Vivek Alwayn
  • Agrawal, Govind P. (2002). Fiber-optic communication systems. New York: John Wiley & Sons. ISBN 0-471-21571-6. 
  1. ^ Alwayn, Vivek (2004-04-23). Splicing. Fiber-Optic Technologies. Cisco Systems. Retrieved on 2006-12-31.
  2. ^ NTT (2006-09-29). 14 Tbps over a single optical fiber: successful demonstration of world's largest capacity. Press release. Retrieved on 2006-12-31.

The Wiley Building in Hoboken, New Jersey, located on the waterfront between River Street and Frank Sinatra Drive. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... April 23 is the 113th day of the year in the Gregorian calendar (114th in leap years). ... For the Manfred Mann album, see 2006 (album). ... December 31 is the 365th day of the year (366th in leap years) in the Gregorian Calendar. ... For the Manfred Mann album, see 2006 (album). ... September 29 is the 272nd day of the year (273rd in leap years) in the Gregorian calendar. ... A news release, press release or press statement is a written or recorded communication directed at members of the news media for the purpose of announcing something claimed as having news value. ... For the Manfred Mann album, see 2006 (album). ... December 31 is the 365th day of the year (366th in leap years) in the Gregorian Calendar. ...

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