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Fiber Optic Glossary

A mechanical media termination device designed to align and join fiber optic connectors. Often referred to as coupling, bulkhead, or interconnect sleeve.

Adapter Sleeve
A mechanical fixture within an adapter body that aligns and holds two terminated fiber connectors. Adapter sleeve material is typically phosphor bronze, ceramic or polymer.
An adapter is a mechanical device designed to align fiber-optic connectors. It contains the split sleeve, also known as the interconnect sleeve, that holds the two ferrules together. Adapters can help mate or connect a variety of fiber optic cables together.
Asymmetric Digital Subscriber Line. Most common form of DSL where the data rate being transmitted to the subscriber is high than the data rate transmitted from the subscriber.

The operation of a sample population of the lasers for an extended period of time under specified conditions.

A device that enlarges and strengthens a signal's output without significantly distorting its original waveshape. There are amplifiers for acoustical, optical and electronic signals.

Signals that are continually changing, as opposed to being digitally encoded.

Analog Signal
An electrical signal that varies continuously over an infinite range of voltage or current values, as opposed to a digital signal, which varies discretely between two values, usually one and zero. It is easiest to think of analog signals as sine waves or various sizes. Compare with Digital Signal.

Analog to Digital Converter
A device that converts an analog signal, that is, a signal in the form of a continuously variable voltage or current, to a digital signal, in the form of bits.

An acronym for American National Standards Institute.

Abbreviation for angled physical contact. A style of fiber optic connector with a 5°-15° angle on the connector tip for the minimum possible backreflection.

Aramid Yarn
Strength elements that provide tensile strength, support and additional protection of the fiber bundles. Kevlar is a particular brand of aramid yarn.

Additional protective element beneath outer jacket to provide protection against severe outdoor environments. Usually made of plastic-coated steel, it may be corrugated for flexibility.

Armadillo Cable Assembly
A ruggedized duplex fiber optic cable assembly featuring rigid plastic connector shell and integrated strain relief boot.

Armadillo Loopback
A ruggedized fiber optic test adapter designed to loop a signal from the Tx side of a port to the Rx side, simulating a complete connection.

Attenuation Limited Operation
The condition in a fiber optic link when operation is limited by the power of the received signal (rather than by bandwidth or distortion).

Attenuation Limited Power
In fiber optics, the limitation on performance imposed by the amplitude of a received signal rather than distortion.

Attenuation Meter
A device used to measure power loss in fiber optic connectors, cables, or systems.

A device that reduces signal power in a fiber optic link by inducing loss.

Abbreviation for American Wire Gauge. Based on a circular mil system. 1 mil equals .001 inch. Used to determine the size of conductors

A transmission network that carries high speed telecommunications between locations. This is normally the main portion of a telecommunication network, with branches going to individual buildings. In a local area network, this is usually the link between routers, switches, and bridges.

The decrease in magnitude of power of a signal in transmission between points. A term used for expressing the total loss of an optical system, normally measured in decibels (dB) at a specific wavelength.

Attenuation Coefficient
The rate of optical power loss with respect to distance along the fiber, usually measured in decibels per kilometer (dB/km) at a specific wavelength. The lower the number, the better the fiber’s attenuation. Typical multimode wavelengths are 850 and 1300 nanometers (nm); single mode wavelengths are 1310 and 1550 nm.

Backbone Cabling
The portion of premises telecommunications cabling that provides connections between telecommunications closets, equipment rooms, and entrance facilities. The backbone cabling consists of the transmission media (optical fiber cable), main and internediate cross-connects, and terminations for the horizontal cross-connect, equipment rooms, and entrance facilities. The backbone cabling can further be classified as interbuilding backbone (cabling between buildings), or intrabuilding backbone (cabling within a building).

Measure of the information-carrying capacity of an optical fiber. Note: This term is often used to specify the normalized modal bandwidth (MHz-km) of a multimode fiber.

Bandwidth Distance Product
The information-carrying capacity of a transmission medium is normally referred to in units of MHz-km. This is called the bandwidth-distance product or, more commonly, bandwidth. The amount of information that can be transmitted over any medium changes according to distance.

Bayonet Coupling
A quick coupling device for plug and receptacle connection, designed to lock a connector into an adapter or receptacle. An example is an ST® connector.

Bend Loss
1. A form of increased attenuation in a fiber that results from bending a fiber around a restrictive curvature (a macrobend) or from minute distortions in the fiber (microbends). 2. A form of increased attenuation caused by allowing high order modes to radiate from the walls of a fiber optic cable. There are 2 common types of bend losses. The first type results when the fiber optic cable is curved through a restrictive radius or curvature. The second type is generally referred to as microbends. It is caused by small distortions of the fiber optic cable imposed by externally induced perturbations as, for example, slip shod cabling techniques.

Bend Radius
The radius of curvature that an optical fiber can bend without sustaining damage.
A branched fiber optic lightguide that performs both receiving and transmitting functions.

Break Out Kit
Used to build up the outer diameter of fiber cable for connecting.

Breakout Cable
A type of fiber optic cable containing several fibers, each with its own jacket and all of them surrounded by one common jacket. Breakout cables are designed for convenient installation of fiber optic connectors but tend to have high transmission losses due to bends in the fibers.

Indicating a capability to deal with a relatively wide spectral bandwidth; high-speed data transmission in which a single cable can carry a large amount of data at once.

Broadband LAN
LAN which uses FDM (frequency division multiplexing) to divide a single physical channel into a number of smaller independent frequency channels. The different channels created by FDM can be used to transfer different forms of information - voice, data, and video.

An electrical or optical pulse that carries information.

A protective material extruded directly on the fiber coating to protect it from the environment (tight-buffered).

Buffer Tubes
Extruded cylindrical tubes covering optical fiber(s) used for protection and isolation. See Loose Tube.

Many individual fibers contained within a single jacket or buffer tube. Also, a group of buffered fibers distinguished in some fashion from another group in the same cable core.

An assembly of optical fibers and other material providing mechanical and environmental protection.

Cable Assembly
Optical fiber cable that has connectors installed on one or both ends. General use of these cable assemblies includes the interconnection of optical fiber cable systems and opto-electronic equipment. If connectors are attached to only one end of a cable, it is known as a pigtail. If connectors are attached to both ends, it is known as a jumper or patchcord.

Cable Bend Radius
Cable bend radius during installation infers that the cable is experiencing a tensile load. Free bend infers a smaller allowable bend radius since it is at a condition of no load.

Central Member
The center component of a cable. It serves as an antibuckling element to resist temperature-induced stresses. Sometimes serves as a strength element. The central member material is either steel, fiberglass, or glass-reinforced plastic.

The material surrounding the core of an optical waveguide. The cladding must have a lower index of refraction to keep the light in the core.

A material put on a fiber during the drawing process to protect it from the environment and handling.

Composite Cable
A cable containing both fiber and copper media per article 770 of the National Electrical Code (NEC).

Connecting Hardware
A device, used to terminate an optical fiber cable with connectors and adapters, that provides an administration point for cross-connecting between cabling segments or interconnecting to electronic equipment.

A mechanical device used to align and join two fibers together to provide a means for attaching to and decoupling from a transmitter, receiver, or another fiber (patch panel).

Connector Panel
A panel designed for use with patch panels; it contains either 6, 8 or 12 adapters pre-installed for use when field-connectorizing fibers.

Connector Panel Module
A module designed for use with patch panels; it contains either 6, 8 or 12 connectorized fibers that are spliced to backbone cable fibers.

The central region of an optical fiber through which light is transmitted.

Unit for measuring the relative strength of ight signals. Normally expressed in dB, it is equal to one-tenth the common logarithm of the ratio of two levels. Expressed in dBm when a power level is compared to a milliwatt.

Non-metallic and therefore, non-conductive. Glass fibers are considered dielectric. A dielectric cable contains no metallic components.

The cause of bandwidth limitations in a fiber. Dispersion causes a broadening of input pulses along the length of the fiber. Three major types are (1) modal dispersion caused by differential optical path lengths in a multimode fiber; (2) chromatic dispersion caused by a differential delay of various wavelengths of light in a waveguide material; and (3) waveguide dispersion caused by light traveling in both the core and cladding materials in single mode fibers.

Fiber Optic Test Procedures. Defined in TIA / EIA Publication Series 455.

Multi-fiber cable constructed in the tight-buffered design. Designed for ease of connectorization and rugged applications for intra-or inter-building requirements.

A mechanical fixture, generally a ceramic tube, used to protect and align a fiber in a connector. Generally associated with fiber optic connectors.

Thin filament of glass. An optical waveguide consisting of a core and a cladding that is capable of carrying information in the form of light. Radius for a fiber can bend before the risk of breakage or increase in attenuation.

Fiber Distributed Data Interface (FDDI)
A standard for a 100 Mbit/s fiber optic local area network.

Fiber Optics
Light transmission through optical fibers for communication signaling.

Fusion Splice
A permanent joint produced by the application of localized heat sufficient to fuse or melt the ends of the optical fiber, forming a continuous single fiber.

Gigahertz (GHz)
A unit of frequency that is equal to one billion cycles per second, 10 Hertz.

Horizontal Cabling
The portion of telecommunications cabling that provides connectivity between the horizontal cross-connect and the work-area telecommunications outlet. The horizontal cabling consists of transmission media, the outlet, the terminations of the horizontal cables, and horizontal cross-connect.

Horizontal Cross-Connect (HC)
A cross-connect of horizontal cabling to other cabling, e.g., horizontal, backbone equipment.

Hybrid Cable
A fiber optic cable containing two or more different types of fiber, such as 62.5 um multimode and single mode.

Jumper (Patchcord)
Optical fiber cable that has connectors installed on both ends.

A unit of force per area expressed in thousands of pounds per square inch. Usually used as the specification for a fiber proof test, e.g., 100 kpsi.

One thousand meters, or approximately 3,281 feet. The kilometer is a standard unit of length measurement in fiber optics. Conversions is 1 ft. = 0.3048 m.

See Local Area Network.

Light Amplification by Stimulated Emission of Radiation. An electro-optic device that produces coherent light with a narrow range of wavelengths, typically centered around 780 nm, 1310 nm, or 1550 nm. Lasers with wavelengths centered around 780 nm are commonly referred to as CD Lasers.

Light Emitting Diode (LED)
A semiconductor device used to transmit light into a fiber in response to an electrical signal. It typically has a broad spectral width.

Local Area Network (LAN)
A geographically limited communications network intended for the local transport of voice, data, and video. Often referred to as a customer premises network.

Loose Tube Cable
Type of cable design whereby coated fibers are encased in buffer tubes offering excellent fiber protection and segregation.

Abbreviation used to denote medium density polyethylene. A type of plastic material used to make cable jacketing.
Main Cross-Connect (MC)

The centralized portion of the backbone cabling used to mechanically terminate and administer the backbone cabling, providing connectivity between equipment rooms entrance facilities, horizontal cross-connects, and intermediate cross-connects.
Mechanical Splicing

Joining two fibers together by permanent or temporary mechanical means (vs. fusion splicing or connectors) to enable a continuous signal. The CamSplice is a good example of a mechanical splice.
Megahertz (MHz)

A unit of frequency that is equal to one million cycles per second.
Micrometer (um)

One millionth of a meter; 10 -6 meter. Typically used to express the geometric dimension of fibers, e.g., 62.5 um.
Mini Bundle Cable
Siecor loose tube cable in which the buffer tube contains two or more fibers, typically 6 or 12 fibers.
A term used to describe an independent light path through a fiber, as in multimode or single mode.
Mode Field Diameter

The diameter of the one mode of light propagating in a single mode fiber. The mode field diameter replaces core diameter as the practical parameter in single mode fiber.
Multi-Fiber Cable

An optical fiber cable that contains two or more fibers.
Multimode Fiber

An optical waveguide in which light travels in multiple modes. Typical core/cladding size (measured in micrometers) is 62.5/125.

Combining two or more signals into a single bit stream that can be individually recovered.
National Electrical Code (NEC)

Defines building flammability requirements for indoor cables. Note: Local codes take precedence but may refer to or require compliance to the NEC.
Nanometer (nm)

A unit of measurement equal to one billionth of a meter; 10 -9 meters. Typically used to express the wavelength of light, e.g., 1300 nm.
Numerical Aperture (NA)

The number that expresses the light gathering ability of a fiber. Related to acceptance angle.
Optical Time Domain Reflectometer (OTDR)

An instrument that measures transmission characteristics by sending a series of short pulses of light down a fiber and providing a graphic representation of the back-scattered light.

Abbreviation used to denote polyethylene. A type of plastic material used for outside plant cable jackets.

Abbreviation used to denote polyvinyl-chloride. A type of plastic material used for cable jacketing. Typically used in flame-retardant cables.

Abbreviation used to denote polyvinyldifluoride. A type of material used for cable jacketing. Often used in plenum-rated cables.

Optical fiber cable that has a connector installed on one end. See Cable Assembly .
PIN Diode

A semiconductor device used to convert optical signals to electrical signals in a receiver.

An air-handling space such as that found above drop-ceiling tiles or in raised floors. Also, a fire-code rating for indoor cable.

An electronic package that converts optical signals to electrical signals.

Reflectance is the ratio of power reflected to the incident power at a connector junction or other component or device, usually measured in decibels or dB. Reflectance is stated as a negative value, e.g., -30 dB. A connector that has a better reflectance performance would be a -40 dB connector or a value less than -30 dB. The terms return loss, back reflection, and reflectivity are also used synonymously in the industry to describe device reflections, but stated as positive values.

A device used to regenerate an optical signal to allow an increase in the system length.

Pathways for indoor cables that pass between floors. It is normally a vertical shaft or space. Also a fire code rating for indoor cable.

A property of glass that causes light to deflect from the fiber and contributes to optical attenuation.
Single Mode Fiber

An optical waveguide (or fiber) in which the signal travels in one mode. The fiber has a small core diameter, typically 9 um.
Splice Closure

A container used to organize and protect splice trays. Typically used in outside plant environments.
Splice Tray
A container used to secure, organize, and protect spliced fibers.

The permanent joining of bare fiber ends to another fiber.
Telecommunications Closet (TC)

An enclosed space for housing telecommunications equipment, cable terminations, and cross-connects. The closet is the recognized cross-connect between the backbone and horizontal cabling. Type of cable construction whereby each glass fiber is tightly buffered by a protective thermoplastic coating to a diameter of 900 micrometers. Increased buffering provides ease of handling and connectorization.

An electronic package used to convert an electrical information-carrying signal to a corresponding optical signal for transmission by fiber. The transmitter is usually a Light Emitting Diode (LED) or Laser Diode.

Underwriters Laboratories, Inc.

The distance between two successive points of an electromagnetic waveform, usually measured in nanometers (nm).
Zero-Dispersion Wavelength

Wavelength at which the chromatic dispersion of an optical fiber is zero. Occurs when waveguide dispersion cancels out material dispersion.

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