# Single-mode optical fiber

﻿
Single-mode optical fiber

In fiber-optic communication, a single-mode optical fiber (SMF) is an optical fiber designed to carry only a single ray of light (mode). This ray of light often contains a variety of different wavelengths. Although the ray travels parallel to the length of the fiber, it is often called the transverse mode since its electromagnetic vibrations occur perpendicular (transverse) to the length of the fiber. Single-mode optical fibers are also called monomode optical fibers, single-mode optical waveguides, or unimode fibers.

Unlike multi-mode optical fibers, single mode fibers do not exhibit modal dispersion resulting from multiple spatial modes. Single mode fibers are therefore better at retaining the fidelity of each light pulse over long distances than are multi-mode fibers. For these reasons, single-mode fibers can have a higher bandwidth than multi-mode fibers. Equipment for single mode fiber is more expensive than equipment for multi-mode optical fiber, but the single mode fiber itself is usually cheaper in bulk.

A typical single mode optical fiber has a core diameter between 8 and 10 µmcite web | title = Fiber Optic Cable Tutorial | url = http://www.arcelect.com/fibercable.htm | author = ARC Electronics | date=2007-10-01 ] and a cladding diameter of 125 µm. There are a number of special types of single-mode optical fiber which have been chemically or physically altered to give special properties, such as dispersion-shifted fiber and nonzero dispersion-shifted fiber. Data rates are limited by polarization mode dispersion and chromatic dispersion. In 2005, data rates of up to 10 gigabits per second were possible at distances of over 60 km with commercially available transceivers (Xenpak). By using optical amplifiers and dispersion-compensating devices, state-of-the-art DWDM optical systems can span thousands of kilometers at 10 Gb/s, and several hundred kilometers at 40 Gb/s.

The lowest-order bound mode is ascertained for the wavelength of interest by solving Maxwell's equations for the boundary conditions imposed by the fiber, which are determined by the core diameter and the refractive indices of the core and cladding. The solution of Maxwell's equations for the lowest order bound mode will permit a pair of orthogonally polarized fields in the fiber, and this is the usual case in a communication fiber.

In step-index guides, single-mode operation occurs when the normalized frequency, "V", is less than 2.405. For power-law profiles, single-mode operation occurs for a normalized frequency, "V", less than approximately $2.405 sqrt\left\{frac\left\{g + 2\right\}\left\{g$, where "g" is the profile parameter.

In practice, the orthogonal polarizations may not be associated with degenerate modes.

ee also

* Optical waveguide
* Multi-mode optical fiber

Notes

References

* Federal Standard 1037C
*

* [http://www.arcelect.com/fibercable.htm The Basics of Fiber Optic Cable]

Wikimedia Foundation. 2010.

### Look at other dictionaries:

• Multi-mode optical fiber — A 1.25 Gbit/s multi mode fiber Multi mode optical fiber (multimode fiber or MM fiber or fibre) is a type of optical fiber mostly used for communication over short distances, such as within a building or on a campus. Typical multimode links… …   Wikipedia

• Optical fiber composite overhead ground wire — (OPGW) is a type of cable that is used in the construction of electric power transmission and distribution lines. Such cable combines the functions of grounding and communications. An OPGW cable contains a tubular structure with one or more… …   Wikipedia

• Optical fiber — A bundle of optical fibers A TOSLINK fiber optic audio c …   Wikipedia

• Optical fiber cable — A TOSLINK optical fiber cable with a clear jacket. These plastic fiber cables are used mainly for digital audio connections between devices. An optical fiber cable is a cable containing one or more optical fibers. The optical fiber elements are… …   Wikipedia

• Optical fiber connector — An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing. The connectors mechanically couple and align the cores of fibers so that light can pass. Better connectors lose… …   Wikipedia

• single-mode fiber —    Optical wave guide that carries only the single wavelength chosen for transmission …   IT glossary of terms, acronyms and abbreviations

• Core (optical fiber) — The structure of a typical single mode fiber. 1. Core 8 µm diameter 2. Cladding 125 µm dia. 3. Buffer 250 µm dia. 4. Jacket 400 µm dia …   Wikipedia

• Fiber to the x — (FTTX) is a generic term for any network architecture that uses optical fiber to replace all or part of the usual copper local loop used for telecommunications. The four technologies, in order of an increasingly longer fiber loop are:* Fiber to… …   Wikipedia

• Fiber-optic communication — An optical fiber junction box. The yellow cables are single mode fibers; the orange and blue cables are multi mode fibers: 50/125 µm OM2 and 50/125 µm OM3 fibers respectively. Fiber optic communication is a method of transmitting information from …   Wikipedia

• Fiber optic sensor — A fiber optic sensor is a sensor that uses optical fiber either as the sensing element ( intrinsic sensors ), or as a means of relaying signals from a remote sensor to the electronics that process the signals ( extrinsic sensors ). Fibers have… …   Wikipedia