Optical Fiber Technology

Optical Fiber is a technology that uses glass (or plastic) threads (fibers) to transmit data. The operation of an optical fibre is based on the principle of total internal reflection. Light reflects or refracts, depending on the angle at which it strikes a surface. A fiber optic system is similar to the copper wire system. The difference is that fiber-optics use light pulses to transmit information down fiber lines instead of using electronic pulses to transmit information down copper lines. Looking at the components in a fiber-optic chain will give a better understanding of how the system works in conjunction with wire based systems.

There are two basic types of fiber used today and many different types of Fiber Optic Cable. The two types of fiber are called Single-Mode fiber (SM) and Multi-Mode fiber (MM):

Multi-mode fiber: It has a large core that allows hundreds of modes of light to propagate through the fiber simultaneously. Multimode fiber is used primarily in systems with short transmission distances (under 2 km), such as premises communications, private data networks, and parallel optic applications.

Single-mode fiber: It has a much smaller core that allows only one mode of light at a time to propagate through the core. Single-mode fibers are designed to maintain spatial and spectral integrity of each optical signal over longer distances, allowing more information to be transmitted. Single-mode fiber is typically used for longer-distance and higher-bandwidth applications.

In addition to the fiber optic cables, other components are required in an optic fiber network. The major components used in a optic fiber network are:

* Fiber Optic Connector: A non-permanent device for connecting two fibers or fibers to equipment where they are expected to be disconnected occasionally for testing or rerouting. It also provides protection to both fibers.

* Ferrule: A tube which holds a fiber for alignment, usually part of a connector

* Splice: a permanent joint between two fibers

* Mechanical Splice: A splice where the fibers are aligned created by mechanical means

* Fusion Splice: A splice created by welding or fusing two fibers together

* Fusion Splicer: An instrument that splices fibers by fusing or welding them, typically by electrical arc.

Key fiber performance specifications:

* Attenuation: The reduction in optical power as it passes along a fiber, usually expressed in decibels (dB). See optical loss

* Bandwidth: The range of signal frequencies or bit rate within which a fiber optic component, link or network will operate.

* Decibels (dB): A unit of measurement of optical power which indicates relative power.

* dB: Optical power referenced an arbitrary zero level

* dBm: Optical power referenced to 1 milliwatt

* Micron (m): A unit of measure used to measure wavelength of light.

* Nanometer (nm): A unit of measure used to measure the wavelength of light (meaning one one-billilonth of a meter)

* Optical Loss: The amount of optical power lost as light is transmitted through fiber, splices, couplers, etc, expressed in dB.

* Optical Power: is measured in "dBm", or decibels referenced to one miliwatt of power.

* Scattering: The change of direction of light after striking small particles that causes loss in optical fibers and is used to make measurements by an OTDR

* Wavelength: A term for the color of light, usually expressed in nanometers (nm) or microns (m).

June 7, 2011

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