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Columbine believes that part of its job is to
educate as well as provide service. To that end, we have provided our Internet
guests with a comprehensive glossary of common cabling/telecommunications industry terms.
The loss of light energy in an optical fiber resulting from impurities in
A cone angled area that light must enter in order to "bounce" down
the fiber, or travel between the core and the cladding.
A mechanical media termination device designed to align and join
fiber optic connectors. Often referred to as a coupling, bulkhead, or
Non-conducting; made entirely of dielectric (insulating) materials,
without any metal conductors.
A format that uses continuous physical variables such as voltage
amplitude or frequency variations to transmit information.
Strength elements that provide tensile strength and provides 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.
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
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); singlemode wavelengths are 1310 and 1550 nm.
Note: When specifying attenuation, it is important to note whether
the value is average or nominal.
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 intermediate
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. See Dispersion for
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. The relationship is not linear,
however. A 500 MHz·km fiber does not translate to 250 MHz for
a 2 kilometer length or 1000 MHz for a 0.5 kilometer length. It is
important, therefore, when comparing media, to ensure that the
same units of distance are being used.
Typically referring to copper, it denotes transmission facilities
capable of handling a wide range of frequencies simultaneously, thus
permitting multiple channels in data systems, rather than direct
(1) A protective material extruded directly on the fiber coating to
protect it from the environment (tight-buffered); (2) extruding a tube
around the coated fiber to allow isolation of the fiber from stresses
in the cable (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.
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 patch cord.
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.
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.
A cabling topology used with centralized electronics connecting the
optical horizontal cabling with intrabuilding backbone cabling
passively in the telecommunications closet.
The material surrounding the core of an optical waveguide. The
cladding must have a lower index of refraction to keep the light in
A material put on a fiber during the draw process to protect it from
the environment and handling.
A cable containing both fiber and copper media per article 770 of
the National Electrical Code (NEC).
Pipe or tubing through which cables can be pulled or housed.
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
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). Commonly used
connectors include the 568SC (Duplex SC), ST® compatible,
FDDI, ESCON, SMA 905/906, Biconic, FC, or D4.
A panel designed for use with patch panels; it contains either 6, 8,
or 12 adapters pre-installed for use when field-connectorizing
Connector Panel Module
A module designed for use with patch panels; it contains either 6 or
12 connectorized fibers that are spliced to backbone cable fibers.
The second manufacturing step in the OVD process; manufacturing
step which removes water vapor from the preform, and sinters it
into a solid, dense, transparent glass blank.
The central region of an optical fiber through which light is
Unit for measuring the relative strength of light signals. Normally
expressed in dB, it is equal to one-tenth the common logarithm of
the ratio of the 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
A data format that uses two physical levels to transmit information
corresponding to 0s and 1s. A discrete or discontinuous signal.
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.
The third and final step in the OVD process; draws the glass blank
into a continuous strand of glass fiber.
An entrance to a building for both public and private network
service cables including the entrance point at the building wall and
continuing to the entrance room or space.
A centralized space for telecommunications equipment that serves
the occupants of a building. An equipment room is considered
distinct from a telecommunications closet because of the nature or
complexity of the equipment.
External; outside the fiber.
Fiber Optic Test Procedures. Defined in TIA/EIA Publication
Siecor multifiber cable constructed in the tight-buffered design.
Designed for ease of connectorization and rugged applications for
intra- or interbuilding requirements.
A mechanical fixture, generally a rigid tube, used to protect and
align a fiber in a connector. Generally associated with fiber optic
Thin filament of glass. An optical waveguide consisting of a core
and a cladding that is capable of carrying information in the form of
Fiber Bend Radius
Radius a fiber can bend before the risk of breakage or increase in
Fiber Distributed Data Interface (FDDI)
A standard for a 100 Mbit/s fiber optic local area network.
Light transmission through optical fibers for communication or
Fresnel Reflection Losses
Reflection losses that are incurred at the input and output of optical
fibers due to the differences in refraction index between the core
glass and immersion medium.
The number of pulses or cycles per second; measured in units of
Hertz (Hz) where 1 hertz equals 1 pulse/cycle per second.
The actual operation of joining fibers together by fusion or by
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.
A unit of frequency that is equal to one billion cycles per second,
Fiber design in which the refractive index of the core is lower
toward the outside of the fiber core and increases toward the center
of the core; thus, it bends the rays inward and allows them to travel
faster in the lower index of refraction region. This type of fiber
provides higher bandwidth capabilities for multimode fiber
The frequency in pulses/cycles per second where 1 hertz equals 1
pulse/cycle per second.
That portion of the 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.
A fiber optic cable containing two or more different types of fiber,
such as 62.5 µm multimode and single-mode.
Institute of Electrical and Electronics Engineers.
A fluid with an index of refraction close to that of glass that reduces
reflections caused by refractive-index differences.
Index of Refraction (IOR)
The ratio of light velocity in a vacuum to its velocity in a given
The portion of the backbone cabling between buildings. See
Intermediate Cross-Connect (IC)
A secondary cross-connect in the backbone cabling used to
mechanically terminate and administer backbone cabling between
the main cross-connect and horizontal cross-connect.
The portion of the backbone cabling within a building. See
Inherent; within; inside the fiber.
Optical fiber cable that has connectors installed on both ends. See
A unit of force per area expressed in thousands of pounds per
square inch. Usually used as the specification for fiber proof test,
e.g., 100 kpsi.
See Aramid Yarn.
One thousand meters, or approximately 3,281 feet, or 0.62 miles.
The kilometer is a standard unit of length measurement in fiber
optics. Conversion 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.
The first step of fiber manufacturing using the OVD process;
deposition of ultrapure vapors around a rotating target rod to form
a glass preform.
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
A telecommunications circuit between any two telecommunications
devices, not including the equipment connector.
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.
A large cable bend that can be seen with the unaided eye; often
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
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.
A unit of frequency that is equal to one million cycles per second.
A decimal unit of measure equaling 3.28 feet.
A small, microscopic bend which may be caused by the cabling
process; mechanical stress due to water in the cable during
repeated freeze and thaw cycles, packaging, or installation.
One millionth of a meter; 10-6 meter. Typically used to express the
geometric dimension of fibers, e.g., 62.5 µm.
Mini Bundle® Cable
Siecor loose tube cable in which the buffer tube contains two or
more fibers, typically 6 or 12 fibers.
Minimum Bend Radius
The amount of bend a fiber (or cable) can withstand before
experiencing problems in performance.
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.
Coding of information onto the carrier frequency. This includes
amplitude, frequency, or phase modulation techniques.
An optical fiber cable that contains two or more fibers.
Multimode Fiber (MM)
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
A telecommunications outlet used to serve more than one work
area, typically in open-systems furniture applications.
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.
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
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 backscattered light.
Outside Vapor Deposition (OVD)
An optical fiber manufacturing method developed, patented, and
used by Corning; manufacturing method using three steps: laydown,
consolidation, and draw.
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
Abbreviation used to denote polyvinyl-difluoride. 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
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.
A connection established between two specific locations as
between two buildings.
Fusing with a low current to clean the fiber end. Precedes fusion
An electronic package that converts optical signals to electrical
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 or electrical 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 (SM)
An optical waveguide (or fiber) in which the signal travels in one
mode. The fiber has a small core diameter, typically 8.3 µm.
A container used to organize and protect splice trays. Typically
used in outside plant environments.
A container used to secure, organize, and protect spliced fibers.
The permanent joining of bare fiber ends to another fiber. See
Fusion Splice and Mechanical Splicing.
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.
Pulling (strength or stress).
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
Total Internal Reflection
Reflection that occurs when a light ray traveling in one material hits
another material and reflects back into the original material without
any loss of light.
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.
Video cameras and cable television.
The portion of the electromagnetic spectrum that can be seen by the
unaided human eye.
The distance between two successive points of an electromagnetic
waveform, usually measured in nanometers (nm).
A range of wavelengths within which a fiber best operates.
Work-Area Telecommunications Outlet
A connecting device located in a work area at which the horizontal
cabling terminates and provides connectivity for work-area patch
Wavelength at which the chromatic dispersion of an optical fiber is
zero. Occurs when waveguide dispersion cancels out material
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