optical fiber

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Related to Optic fiber: fiber optic cable, sound barrier

optical fiber

[′äp·tə·kəl ′fī·bər]
(optics)
A long, thin thread of fused silica, or other transparent substance, used to transmit light. Also known as light guide.

optical fiber

optical fiber

A thin glass strand designed for light transmission. A single hair-thin fiber is capable of transmitting trillions of bits per second. In addition to their huge transmission capacity, optical fibers offer many advantages over electricity and copper wire. Light pulses are not affected by random radiation in the environment, and their error rate is significantly lower. Fibers allow longer distances to be spanned before the signal has to be regenerated by expensive "repeaters." Fibers are more secure, because taps in the line can be detected, and lastly, fiber installation is streamlined due to its dramatically lower weight and smaller size compared to copper cables.

Starting in the 1970s
In the late 1970s and early 1980s, telephone companies began to use fibers extensively to rebuild their communications infrastructure. According to KMI Corporation, specialists in fiber optic market research, by the end of 1990 there were approximately eight million miles of fiber laid in the U.S. (this is miles of fiber, not miles of cable which can contain many fibers). By the end of 2000, there were 80 million miles in the U.S. and 225 million worldwide. Fiber is also used to replace copper cable for LAN backbones.

Pure Glass
An optical fiber is constructed of a transparent core made of nearly pure silicon dioxide (SiO2), through which the light travels. The core is surrounded by a cladding layer that reflects light, guiding the light along the core. A plastic coating covers the cladding to protect the glass surface. Cables also include fibers of Kevlar and/or steel wires for strength and an outer sheath of plastic or Teflon for protection.

Enormous Bandwidth
For glass fibers, there are two "optical windows" where the fiber is most transparent and efficient. The centers of these windows are 1300 nm and 1550 nm, providing approximately 18,000 GHz and 12,000 GHz respectively, for a total of 30,000 GHz. This enormous bandwidth is potentially usable in one fiber. The only limitation is the electronic circuits that modulate the light waves to represent the data. Electronic ciruits have yet to come close to the frequencies of light.

Singlemode and Multimode
There are two types of glass fiber. For intercity cabling and highest speed, singlemode fiber with a core diameter of less than 10 microns is used. Multimode fiber is very common for short distances and has a core diameter from 50 to 100 microns.

Plastic Fiber Too
For short-distance runs such as within buildings, plastic fiber is also used, and their transparent windows are typically 650 nm or within the 750-900 nm range. Plastic optical fiber (POF) is easier to install than glass but requires repeaters for distances greater than 100 meters. See laser, WDM, fiber optics glossary and cable categories.


Fiber Strands
The fibers in this picture are being prepared for splicing in a wiring closet. These few strands can collectively transmit trillions of bits per second. (Image courtesy of Corning Incorporated.)







Fiber Vs. Copper
Not only does optical fiber offer enormous bandwidth, but it takes a lot less room. Any one of these copper bundles can be replaced with one fiber strand (center). (Image courtesy of Corning Incorporated.)







Fiber-Optic Cable
This Lucent fiber-optic cable holds 288 fibers, which was a record-high fiber count in 1996. Cables with more than a thousand fibers have since been developed.








Laying Optical Fiber
Embedding thousands of miles of fiber in the ground has been a Herculean feat undertaken by many companies. In time, all copper wires are expected to give way to fiber. (Image courtesy of Metromedia Fiber Network.)
References in periodicals archive ?
Telecommunications companies are behind the delay in completion of the optic fiber because if it is executed, no one will use internet services of mobile phone companies", another resident of the city, Mohammad Ashraf, believes
The optic fiber projects are also being carried out in Sindh and Balochistan aimed at providing infrastructure for provision of basic telephony services in these provinces.
A very important role is played by optic fiber guiding mechanism on both sides of the electrodes (3, fig.
He affirmed that the company will start implementing some projects for optic fiber deployment in the wilayats of Sohar, A'Suwaiq and Al Musannah in the Governorate of North Al Batinah and other areas as well concurrently with the projects implemented by the Ministry of Regional Municipalities and Water Resources and the Public Authority for Electricity and Water (PAEW).
She said, "An Optic Fiber Cable of about 40 km has been laid and has proved to be an asset for a populace of about 101,000 people and further initiatives will be taken in future by the Ministry of IT to spread Optic Fiber across all the Union Council's of Pakistan to connect the entire nation".
The minister revealed that 20 percent work on the optic fiber project could not be completed in some provinces for security reasons.
Japan's biggest optic fiber maker, said Monday it has sealed a deal to sell part of its stake in U.
NTT) group firm will use optic fiber networks instead of phone switchboards, which are more expensive.
In the end, it sucked the life out of the Spring Street District, which remains blighted in spite of an influx of high-tech firms seeking convenient hookups to existing optic fiber lines.
The MoU aims at benefiting from the projects at the Wilayat of Salalah in Dhofar Governorate in relation to optic fiber cables deployment.
Tyagi said : "We are working on innovative initiatives and creating data-oriented infrastructure for next generation services that include 3G GSM backhaul connectivity and IP leased lines simulation from national optic fiber network.
The USF is also successfully running programmes for providing basic telephony and data services, optic fiber connectivity to the Tehsils, broadband internet to 2nd & 3rd tier cities and towns and bringing broadband to the villages through tele-centers.