Optical fiber Guide, Meaning , Facts, Information and Description
optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light.Fiber optics is the branch of science and engineering concerned with optical fibers.
The optical fiber can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables. Although fibers can be made out of either plastic or glass, the fibers used in long-distance telecommunications applications are always glass, because of the lower optical absorption of glass. The light transmitted through the fiber is confined due to total internal reflection within the material. This is an important property that eliminates signal crosstalk between fibers within the cable and allows the routing of the cable with twists and turns. In telecommunications applications, the light used is typically infrared light, at wavelengths near to the minimum absorption wavelength of the fiber in use.
Fibers are generally used in pairs, with one fiber of the pair carrying a signal in each direction.
Fibers, like waveguides, can have various transmission modes. The fibers used for long-distance communication are known as single mode fibers, as they have only one strong propagation mode. This results in superior performance compared to other, multi-mode fibers, where light transmitted in the different modes arrives at different times, resulting in dispersion of the transmitted signal. Typical single mode fibre optic cables can sustain transmission distances of 80 to 140km between regenerations of the signal, whereas most multi-mode fibre have a maximum transmission distance of 300 to 500 metres. Single-mode fibres most commonly have a diameter of 9um, while multi-mode fibres are available with 50um or 62.5um diameters.
Because of the remarkably low loss and excellent linearity and dispersion behavior of single-mode optical fiber, data rates of up to 40 Gbit/s are possible in real-world use on a single wavelength. Wavelength division multiplexing can then be used to allow many wavelengths to be used at once on a single fiber, allowing a single fiber to bear an aggregate bandwidth measured in terabits per second.
Modern fiber cables can contain up to a thousand fibers in a single cable, so the performance of optical networks easily accommodate even today's demands for bandwidth on a point-to-point basis. However, unused point-to-point potential bandwidth does not translate to operating profits, and it is estimated that no more than 1% of the optical fiber buried in recent years is actually 'lit'.
Modern cables come in a wide variety of sheathings and armor, designed for applications such as direct burial in trenches, installation in conduit, lashing to aerial telephone poles, submarine installation, or insertion in paved streets. In recent years the cost of small fibre-count pole mounted cables has greatly decreased due to the high Japanese and South Korean demand for Fiber to the Home (FTTH) installations.
Recent advances in fiber technology have reduced losses so far that no amplification of the optical signal is needed over distances of hundreds of kilometers. This has greatly reduced the cost of optical networking, particularly over undersea spans where the cost reliability of amplifiers is one of the key factors determining the performance of the whole cable system. In the past few years several manufacturers of submarine cable line terminal equipment have introduced upgrades that promise to quadruple the capacity of older submarine systems installed in the early to mid 1990s.
Longer-range systems still have to use optical amplifiers.
| Table of contents |
|
2 Advantages of optical fibers over wires 3 Disadvantages of optical fibers compared to wires 4 History |
In an optical fiber, a refracted ray is one that is refracted from the core into the cladding. Specifically a ray having direction such that where r is the radial distance from the fiber axis, φ(r ) is the azimuthal angle of projection of the ray at r on the transverse plane, θ(r ) is the angle the ray makes with the fiber axis, n (r ) is the refractive index at r , n (a ) is the refractive index at the core radius, a . Refracted rays correspond to radiation modes in the terminology of mode descriptors.
For the fiber to guide the optical signal, the refractive index of the core must be slightly higher than that of the cladding. In different types of fibers, the core and core-cladding boundary function slightly differently in guiding the signal. Especially in single-mode fibers, a significant fraction of the energy in the bound mode travels in the cladding.
Source: from Federal Standard 1037C
Refracted rays
Advantages of optical fibers over wires
Disadvantages of optical fibers compared to wires
class="external">[1
History
In 1966, Charles Kao, born in China, in his PhD thesis estimates that glass fibers need to have an optic signal attenuation of less than 20 dB per kilometer to be useful for long distance communication. The first useful optical fiber was invented in 1970 by researchers Maurer, Keck, Schultz, and Zimar working for American glass maker Corning Glass Works (http://www.corning.com/). They manufactured a fiber with 17 dB optic attenuation per kilometer by doping silica glass with titanium.
The first transatlantic telephone cable to use optical fiber was TAT-8, which went into operation in 1988.
Waveguides are silicon chips with extremely thin and extremely flexed optical fibers on them. Companies like JDSUniphase (http://www.JDSU.com) manufacture these waveguides for use in computers and in spliting boxes. A waveguide separates the different colors of light, and allows it to have the same signal sent in many directions to put it simply (see waveguides)
This is an Article on Optical fiber. Page Contains Information, Facts Details or Explanation Guide About Optical fiber Other uses of optical fibers
Optical fiber in waveguides
See also
External links