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Glossary

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A

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• Absorption

The loss of light energy in an optical fiber resulting from impurities in the glass.

• Acceptance Cone

A cone angled area that light must enter in order to "bounce" down the fiber or travel between the core and the cladding.

• Acrylate

Acrylic resin


• Adapter

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


• ADSL2

A high speed ADSL technology defined by ITU G.992.3/4, capable of 12 Mbps downstream.

• ADSL2+

A high speed ADSL technology defined by ITU G.992.5, capable of 24 Mbps downstream.

• All-dielectric

Non-conducting; made entirely of dielectric (insulating) materials, without any metal conductors


• American National Standards Institute (ANSI)

A member of ISO, ANSI accredits and implements standards.


• Analog

A format that uses continuous physical variables such as voltage amplitude or frequency variations to transmit information.


• Angled Polish Connector / APC

Connectors which have their end-face (mating surface) polished at an 8 degree angle to the fiber axis. Minimizes reflections; required in RF video applications.


• Aramid Yarn

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


• Architecture

Describes how network elements logically relate to each other.


• Armor

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


• Armoring

Protective element (usually of steel wires or strips) used in cables for special service conditions, as in undersea and mining applications, rodent protection etc. It is applied over
the cable sheath.

• Arrester

Passive electrical component for diverting overvoltage towards ground potential. When the nominal response voltage is reached, an arc is generated which reduces the resistance of the discharge path between the electrodes. The resulting dangerous current is discharged to ground.


• Asymmetric Digital Subscriber Line (ADSL)

A variant of DSL providing higher downstream data rate (to the customer site) than upstream (to the service provider).


• Asymmetric rate

The ability of a device to transmit at a different rate than it receives.

• Asynchronous Transfer Mode (ATM)

A high-speed, low-delay, connection-oriented switching and multiplexing technique using 53 byte – cells to transmit different types of data concurrently across a single physical link.


• Attenuation

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. Note: When specifying attenuation, it is important to note whether the value is average or nominal.


• Attenuation Test Set

Test set having a calibrated light source and meter; used to measure the power loss in an optical link or network.


• ATU ADSL Transmission Unit

ATU-C stands for ADSL Termination Unit - Central (Office).
ATU-R stands for ADSL Termination Unit - Remote.
These two devices are the ADSL modems situated on either side of the telco copper loop. In other words, the ATU-C / R are fancy words for ADSL modems. The ATU-C is packaged into the central office type equipment. The ATU-R is a self-contained box suitable for customer use, including an AC adapter for powering.

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• 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 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).


• Bandwidth

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 single-mode fibers.


• 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. 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.


• Broadband Passive Optical Network (BPON)

System described in ITU G983 standard. Uses optical splitters to create a one-to-many relation between the CO/HE and the subscribers. Capable of delivering voice and data; usually combined with a RF overlay for video. Usually no active (powered) components between CO/HE and subscriber.

• Broadband

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 modulation.


• Brownfield

Existing MDUs and/or neighborhoods already served by at least one provider.

• Buffer Tubes

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

• Buffering

(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).

• Building Homerun

MDU topology in which each subscriber’s fiber link runs all the way to a common point for the entire building (usually a terminal in the basement or mounted on an outside wall).

• Bulk Cable

Cable, such as drop, purchased in long lengths, on spools or reels and placed/cut to length and terminated on site.

• Bundle

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, such as with colored binder threads.

• Butt Coupling (butt joint, butted fibers)

Signal transmission across fibers joined together end to end.

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• Cable

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 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.

• Cable Sheath

Sheath or jacket usually of polyethylene (PE) or poly-vinylchloride (PVC) which protects the core from environmental influences.


• Category 3 (CAT. 3)

A level of unshielded twisted-pair wiring performance as defined by EIA / TIA-568. CAT. 3 is specified up to 16 MHz.

• Category 3, 5, 6 (CAT. 3, 5, 6)

Cable and optical fibre connector categories in accordance with ISO / IEC DIS 11801 and EN 50173. Each category (CAT.) requires specific values for transmission parameters such as attenuation and near-end crosstalk attenuation.

• Category 5 (CAT. 5)

A level of unshielded twisted-pair wiring performance as defined by EIA / TIA-568. CAT. 5 is specified up to 100 MHz.

• CATV (Cable TV)

CATV networks are distribution networks in which the various television programs are transmitted over tree-configured coaxial cables and large amplifier cascades to the subscriber.

• Central Member

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

• Central Office (CO)

The telephone company’s central location containing active (powered) equipment, from which services are provided. May contain telephone switching equipment and/or optical line terminals and RF video for BPON and GPON systems.

• Centralized Cabling

A cabling topology used with centralized electronics connecting the optical horizontal cabling with intrabuilding backbone cabling passively in the telecommunications closet.

• Circuit Interrupter

faults to ground and immediately shuts off the flow of electricity.
Required for most outdoor, basement and garage, kitchen and bathroom outlets.

• Cladding

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.

• Coating

A material applied to a fiber during the draw process to protect it from the environment and handling.

• Coaxial

Asymmetric copper cable with a characteristic impedance of 75 Ω.

• Composite Buffered Fiber

Combination of single-fiber loose buffer and tight buffered fiber. The slight gap between fiber and buffer tube is filled with a gliding layer.

• Composite Cable

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

• Conduit

Pipe or tubing through which cables can be pulled or housed.


• Connecting Hardware

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

• Connector

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.

• Connector Panel

A panel insert designed for use with patch panel housings. Connector panels often contain either 6, 8, or 12 adapters pre-installed for use when field-connectorizing fibers.


• Connector Panel Module

A connector panel module designed for use with patch panels. It contains either 6 or 12 connectorized fibers that are spliced to backbone cable fibers.


• Consolidation

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.

• Core

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


• Core Glass

Core of an optical fiber with a refractive index higher than that of the cladding glass.


• Coupler

Passive component for transmitting / branching light to one or more fibers. The incoming optical power is divided up or, viewed in the opposite direction, merged together.

• Coupling

See Adapter.


• Cross-connection cabinet

Copper cable distribution cabinet with IDC modules, terminating the high pair count cable coming from the CO and distributing low pair count cables going to the subscribers. The cabinet is located close to the subscribers.

• Cross-jumpering

Horizontal jumpering in the main distribution frame, e.g. between the horizontal levels of a distribution frame.

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• Decibel (dB)

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.

• Deutsches Institut für Normung (DIN)

German Institute for Standardization.


• Dielectric

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

• Digital

A data format that uses two physical levels to transmit information corresponding to 0s and 1s. A discrete or discontinuous signal.


• Digital Subscriber Line (DSL)

A family of digital telecommunications protocols designed to allow high speed data communication over the existing copper telephone lines between end-users and telephone companies.

• Digital Subscriber Line Access Multiplexer (DSLAM)

A platform for DSL modems that provides high-speed data transmission over traditional twisted-pair wiring.


• Dispersion

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.


• Distribution (Cable)

That part of the fiber-to-the-home network between the optical splitter and the start of the drop cable.


• Draw

The third and final step in the OVD process; draws the glass blank into a continuous strand of glass fiber.


• Drop (Cable)

The last link in the fiber-to-the-home network, this cable typically serves just one subscriber.


• Dropwire

Outside wire pair(s) from the central office to a house or building for termination and optional connection to a protector.


• Duplex Connector

Two fiber optic connectors held together by a clip or by design usually to provide go and return paths.


• Duplex Operation (two-path transmission)

Information transmission in both directions on one fiber.

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• Electronic Industries Association (EIA)

This organization provides standards for the data communications industry to ensure uniformity of interface between DTEs and DCEs.

• Electronic Industries Association / Telecommunications Industry association (EIA / TIA)

This organization provides standards for the data communications industry to ensure uniformity of the interface between DTEs (Data Terminal Equipment) and DCEs (Data Communications Equipment).

• EN

European Norm

• Entrance Facility

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.

• Equipment Room

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.

• ETSI European Telecommunications Standards Institute

An organization that defines technical standards in the area of telecommunications.


• Extrinsic

External; outside the fiber.

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• Fan-Out

Corning Cable Systems tight-buffered breakout style multifiber cable designed for ease of connectorization and rugged applications for intra- or interbuilding requirements.

• Ferrule

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


• Fibre Distributed Data Interface (FDDI)

A standard for a 100 Mbit/s fibre optic local area network.


• Fibre

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.


• Fibre Amplifier

special fiber containing, as an additive, the element erbium. Laser light pumped into this special section of fiber excites the valence electrons in the erbium. When the transmitted signal passes through the fiber, the excited electrons give up their extra energy in sync with the transmitted signal, adding to its strength. The output is identical to the input, but now has a much higher power level. EDFAs amplify the optical signal without the need to convert it to an electrical signal and back to optical.


• Fibre Bend Radius

Radius a fiber can bend before the risk of breakage or increase in attenuation.

• Fibre Multiplexing

Transmission method in which each transmission channel is assigned a fibre.


• Fiber Optics

Light transmission through optical fibres for communication or signaling.


• Fibre to the x / FTTx

Refers to a host of acronyms based on taking fibre to the home (FTTH), node (FTTN), curb (FTTC), etc.


• FOTP

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


• Frequency

The number of pulses or cycles per second; measured in units of Hertz (Hz) where 1 hertz equals 1 pulse/cycle per second.


• 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.


• FRNC

Flame Retardant Non Corrosive LSZH Material.


• Functional element

The functional elements are part of distribution blocks and contain the IDC contacts along with contact springs for the protection magazine contacts.


• Fusing

The actual operation of joining fibers together by fusion or by melting.


• Fusion Splicing

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.

• Future-Proofing

Design decision process in which elements that may not be required today, but which are very likely to be needed in the future, are either built into the design up front or are planned as simple upgrades.

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• Gigabit Passive Optical Network / GPON

Similar to BPON, but based on higher gigabit speeds. Like BPON, these systems may use an RF overlay for video, but because of their increased bandwidth per subscriber, are also being used for IPTV deployment, in which all services (voice, video and data) are placed on the GPON and the RF video overlay is not required.


• Gigahertz (GHz)

A unit of frequency that is equal to one billion cycles per second, 109 Hertz.


• Graded-Index

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 transmission.


• Graded-Index Fiber

The graded-index fiber is an optical waveguide with a graded-index profile.


• Graded-Index Profile

Refractive index of a fiber that decreases in a parabolic curve with increasing distance from the center of the fiber core cross section.


• Greenfield

New construction of MDUs and neighborhoods. In this case, no service provider and no network exists. Fiber can be planned and placed efficiently while walls, ceilings basements and attics are openly accessible to create pathways.


• GRP Element

Support and tensile strength member made from glass filaments (GRP glass fiber reinforced plastic).

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• Head End

HE Cable TV term analogous to the telephone company’s central office.


• Hertz (Hz)

The frequency in pulses/cycles per second where 1 hertz equals 1 pulse/cycle per second.


• Home Phone Network Alliance

HPNA HPNAv3 – technology that can use existing copper phone lines or coax lines to deliver broadband services.


• Homerun

Installation in which cables are pulled from each outlet or device back to a one common location, such as the ONT in a living unit or from each living unit to a common location for the MDU building.


• Horizontal Cabling

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.


• Hybrid Cable

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


• Hz Hertz

A unit of frequency that equals one cycle per second.

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• IEC

International Electrical Standards

• IEEE

Institute of Electrical and Electronics Engineers.

• Index of Refraction (IOR)

The ratio of light velocity in a vacuum to its velocity in a given transmission medium.

• Index-Matching Fluid

A fluid with an index of refraction close to that of glass that reduces reflections caused by refractive-index differences.


• Indoor Cable

Cables for applications inside buildings. They are not generally suitable for installation outdoors.


• Insertion Loss

The transmission quality of a connector is judged by reference to its insertion loss, i.e. by determining the extent to which the attenuation of an optical transmission path increases when a connector is inserted in this path.

• Inside Wiring (IW)

The communications wiring inside a home or living unit. Includes phone, data and CATV (coax) wiring.


• Insulation Displacement Connection (IDC)

The IDC contact allows copper cables to be connected without soldering, screwing or stripping the wire pairs.

• Integrated Services Digital Network (ISDN)

Telecommunication service that uses digital transmission and switching technology to provide voice and digital data communications on a bearer channel (B-channel) while sending signalling on the data channel (D-channel).

• Interbuilding Backbone

The portion of the backbone cabling between buildings. See Backbone Cabling.


• 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.


• Intermediate Terminals

Topology in which multi-fiber cables are run (usually in a riser) to serve terminals (MDU terminals) placed on multiple floors. This approach is used in larger MDUs to consolidate individual drops into larger cables that can be easily connected in a central point in the building.


• International Protection (IP)

International Protection is a worldwide standard described in the norm IEC 529 which defines degrees of protection against water, dust and solid objects.

• International Standardisation Organisation (ISO)

Worldwide federation of national standards bodies concerned with consistent rules or guidelines of technical specifications.


• International Telecommunications Union (ITU)

The telecommunications agency of the United Nations, established to provide standardized communications procedures and practices. Before March 1993 it was called CCITT.

• Internet Protocol Television (IPTV)

Use of Internet protocol to handle transmission of television signals over a data network (instead of doing so over a radio frequency (RF) network such as cable TV). Allows the television signals to be sent over the same “pipe” as data and voice.

• Internet Service Provider (ISP)

A company that provides access to the internet.


• Intrabuilding Backbone

The portion of the backbone cabling within a building. See Backbone Cabling.


• Intrinsic

Inherent; within; inside the fiber.

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• Jumper

Optical fiber cable that has connectors installed on both ends. See Cable Assembly.

• Jumper comb

Metal / plastic strip with open or closed jumpering loops, fixed at the rear of the distribution blocks. It is used for organizing the wire bundle. The jumpering loops are closed on the jumper side and open on the cable side.


• Jumpering

The subscriber lines are connected with the system lines via a jumper wire pair (line between the subscriber and system connection).

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• Kevlar®

See Aramid Yarn.

• Kilohertz (kHz)

A unit of frequency equal to 1,000 cycles per second.

• Kilometer (km)

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.

• kpsi

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.

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• LASER Diode

Light Amplification by Stimulated Emission of Radiation. A laser diode is 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.


• Launch Angle

Angle between the direction of propagation of the incident light and the optical axis of an optical fiber. For the incident light to be launched, this angle must be between zero and a maximum value which is dependent on the point of incidence at the fiber endface and on the difference in refractive index at that point and at the cladding.


• Laydown

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 width.


• Light Waves

Electromagnetic waves in the region of optical frequencies. The term light originally referred merely to the radiation visible to the human eye with a wavelength between 400 and 800 nm. It is however usual to call radiation in the bordering spectral ranges (e.g. infrared) light also.

• Line card

Computer card of the switching system. 8, 16, 32 or more subscribers are supported by a single line card.

• Link

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.


• Local Convergence Point

LCP That point in the network, usually a cabinet or closure, that marks the breakout from the feeder cable (from the CO/HE) to the distribution cables that go through a neighborhood or MDU. The LCP usually contains optical splitters.

• Loose-Tube Cable

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

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• Macrobend

A large cable bend that can be seen with the unaided eye; often reversible.

• 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.

• Main Distribution Frame (MDF)

The main distribution frame is the interface between the subscriber cables and the switching system. Subscriber and system cables are connected to the main distribution frame and are jumpered, tested and protected against overvoltage and overcurrent.


• MDPE

Abbreviation used to denote medium density polyethylene; a type of plastic material used to make cable jacketing.


• MDU Terminal

The MDU terminal serves as an interconnection between a distribution cable (with many fibers) and individual drops going to subscriber living units. This is usually a small cabinet or enclosure; in some cases, it may contain splitters. It can be located inside or on the exterior of an MDU.

• 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.


• Meter

3.28 feet.

• Metropolitan Area Network (MAN)

Data network system permitting data and voice transmission. Links LANs in cities to provide better performance than is possible with WANs.

• Microbend

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.

• Microduct

Small (usually less than half an inch (<13 mm) duct installed in MDUs to protect single-fiber drop cables. It also makes it possible to easily remove/replace drops in the event of damage.

• Micrometer (µm)

One millionth of a meter; 10-6 meter; typically used to express the geometric dimension of fibers, e.g., 62.5 µm.

• Migration

The process of moving from one cabling system or technology to another, such as migrating from a copper to optical network.


• Minimum Bend Radius

The amount of bend a fiber (or cable) can withstand before experiencing problems in performance.


• Mode

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.


• Modulation

Coding of information onto the carrier frequency. This includes amplitude, frequency, or phase modulation techniques.


• Mounting chassis

Metal chassis of a distribution block containing the functional elements and wire guides.

• Multidwelling Unit (MDU)

A building structure that has two or more residential dwelling units occupied by separate entities. The living units may be owned individually or the entire building may be owned as one property with units rented to tenants.


• Multifiber Cable

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 sizes (measured in micrometers) are 62.5/125.


• Multiplex

Combining two or more signals into a single bit stream that can be individually recovered.


• Multi-User Outlet

A telecommunications outlet used to serve more than one work area, typically in open-systems furniture applications.

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• 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.


• National Electrical Code® (NEC)®

An advisory document published by the NFPA and which includes building flammability requirements for indoor cables.
Note: Local codes take precedence but may refer to or require compliance to the NEC.

• Network Interface Device (NID)

A device that connects the local loop to the customer premises and includes the demarcation point.


• NEXT Near End cross (x) Talk

Crosstalk in which the interfering signal is travelling in the opposite direction as the desired signal.


• Numerical Aperture (NA)

The number that expresses the light gathering ability of a fiber; related to acceptance angle or the difference in index of refraction between the core and the cladding.

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• Open Systems Interconnection (OSI)

The seven-layer architecture of data communication protocols developed by ISO and ITU.

• Optical Fiber

See Fiber.

• Optical Line Terminal (OLT)

For BPON and GPON systems, this is the electronics that reside in the CO/HE and which control the ONTs served at each subscriber’s location. Typically, OLTs service 16, 32 or 64 ONTs.


• Optical Network Terminal (ONT)

For BPON and GPON systems, this is the electronics located at the subscriber’s premises. The ONT converts the optical signal to copper and coax-based signals for connection to phones, computers and televisions in the residence.


• Optical Return Loss (ORL)

For an optical network, as a system, ORL is a measure of the total reflected signal relative to the signal being transmitted into the network (the incident signal). ORL includes all components, end to end, such as fiber, connectors, splices, etc. in the link. ORL is expressed as a positive value, and the larger the value, the better
the performance. For example, 60 dB means the total signal reflected back is 60 dB below the incident being transmitted into the network.

• Optical Time Domain Reflectometer (OTDR)

A test set that sends out light and senses light scattered and reflected back to the set. It is capable of showing the distance to faults and other “events” in an optical cable, as well as the attenuation (power loss) associated with each event.

• Optical Waveguide

Transparent dielectric waveguide for the transmission of electromagnetic waves in the region of visible light.


• Outdoor Cable

Cables which are designed to meet all the requirements encountered in buried and ducted cable systems.

• Outside Plant (OSP)

Cabling outside of buildings, including aerial and buried installations.

• Outside Vapor Deposition (OVD)

An optical fiber manufacturing method developed, patented, and used by Corning; manufacturing method using three steps-laydown, consolidation, and draw.

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• Passive Optical Network (PON)

A passive network for FITL with passive components such as couplers,  splitters and connectors.


• Pathway

The path planned and used for cable placement. It includes ducts, raceway, aerial strand, etc.

• PE

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


• Pigtail

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.

• Plain Old Telephone Service (POTS)

Standard telephone service over the PSTN, with an analogue bandwidth of less than 4 kHz.

• Plain Old Telephone Service Splitter (POTS splitter)

A device that filters out the DSL signal and allows POTS frequencies to pass through.

• Plenum

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


• Point-to-Point

A connection established between two specific locations as between two buildings.


• Port

An access point for data entry or exit.

• Positive Temperature Coefficient (PTC)

Passive semiconductor to limit overcurrent. When the nominal response current is reached, the PTC heats up to reach high resistance, thus limiting the current.


• Preconnectorized

Cables having optical connectors pre-installed and tested at a factory before being shipped to the field for installation as an assembly.

• Prefusing

A low current electric arc used to clean the fiber end prior to fusion splicing.


• Pre-Stubbed

Hardware (such as an LCP cabinet) that has a factory-connectorized or factory-prepared cable (stub) built into it. In the field, the hardware is placed and the stub cable is spliced into the system. The work of connectorizing each fiber or preparing the cable inside the cabinet is already complete, saving field time and labor.

• Private Branch Exchange (PBX)

Telephone switching equipment spent for one customer. A PBX connects private telephones to each other and to the public dial network.


• Public Switched Telephone Network (PSTN)

A network shared among many users who can use telephones to establish connections between two points. Also known as dial network.


• PVC

Abbreviation used to denote polyvinyl-chloride; a type of plastic material used for cable jacketing; typically used in flame-retardant cables.


• PVDF

Abbreviation used to denote polyvinyl-difluoride; a type of material used for cable jacketing; often used in plenum-rated cables.

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• QAM - Quadrature Amplitude Modulation

A line code using phase and amplitude changes to send digital data over an analogue carrier.

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• Raceway – Decorative

Usually a surface-mounted pathway, such as a crown molding, that is used to hide and protect a cable.

• Rate Adaptive Digital Subscriber Line (RADSL)

A method to use an existing twisted-pair line that permits simultaneous POTS and high-speed data communication at adaptive symmetric and asymmetric rates.


• Receiver

An electronic package that converts optical signals to electrical signals.

• Reflectance

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.


• Refractive Index

The factor by which the velocity of light in an optical medium (e.g. glass) is less than it is in vacuum.

• Remote Digital Line Unit (RDLU)

Remote unit containing switching and copper wire technology. It is basically a small central office located close to the subscriber.


• Remote Termination Unit (RTU)

A DSL device installed at the customer premises.

• Repeater

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


• Return Loss

See Reflectance.

• RF Video Overlay

Use of an RF video signal, usually at a separate wavelength from the data/voice transmission to provide television/video services.
The transmission technique is similar to that used for CATV.

• RH

Relative Humidity.

• Ribbon Fiber

The fibres are arranged parallel to each other and joined together equally spaced in a flat plane (e.g. bonded directly or between two adhesive films); several ribbons can be grouped into stacks inside a cable.


• Riser

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


• RJ11

A 4 pin connector used for voice and/or data transmission over standard copper telephone cable.

• RJ45

Registered Jack-45, an eight-wire connector used to connect computers onto a local-area networks (LAN), especially Ethernets. RJ-45 connectors look similar to the RJ-11 connectors used for connecting telephone equipment, but they are a bit wider.


• Rough-in

Phase of construction when walls and ceilings are framed, but not yet covered with finishing materials. At this point, the hiddenelements of electrical and communications, plumbing, HVAC and other systems can be installed. Once wall and ceiling finishing materials are installed, these systems also receive their finishing work in the form of outlet plates, fixtures, grates and so on. It is during rough-in that microduct, cabling and wiring boxes can be installed to make service connections easy to complete after the building is finished.

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• Scattering

The loss of signal power (light) from the fiber core caused by impurities or changes in the index of refraction of the fiber.


• Self-Contained Distribution

An MDU topology element in which splitters are placed in the same building as the subscribers they serve. Therefore the entire distribution portion of the network is contained within the building.

• Shared Distribution

An MDU topology element in which splitters are external to the building and the subscribers they serve. Usually, two or more buildings share a common splitter location (LCP).

• Shielded Twisted Pair (STP)

A cable consisting of one or more pairs of wires twisted together and wrapped with shielding foil.

• Single-Mode Fibre (SM)

An optical waveguide (or fibre) in which the signal travels in one mode. The fibre has a small core diameter, typically 8.3 µm.


• Single-pair High-speed Digital Subscriber Loop (SHDSL)

A synonym for the ITU recommendation G.991.2. SHDSL is designed as a substitute for SDSL, HDSL, and other DSL services.


• 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.

• Splicing

The permanent joining of bare fiber ends to another fiber. See Fusion Splice and Mechanical Splicing.


• Splitter

Optical component for distributing the optical power from one fiber to several other fibers.

• Splitter (Optical)

An optical device which splits the optical power of one signal into multiple outputs, each containing the same signal, but at a lower power level. For BPON and GPON systems, splits of 1x16, 1x32 and 1x64 are used.

• Star Coupler

Active or passive component providing a uniform distribution of optical power between equal numbers of incoming and outgoing fibers.

• Step-Index Profile

Fiber with the refractive index declining abruptly between core and cladding but staying constant within the core and cladding themselves.

• Subscriber lines / cables

Lines connecting the subscribers with the main distribution frame

• Switching system

The switching system connects the subscribers with one another. The subscribers are stored on the line card.

• Symmetric Digital Subscriber Line (SDSL)

A method to use an existing twisted-pair line that permits high bandwidth, bidirectional transmission.

• Synchronous Transfer Mode (STM)

Transport and switching of digital data in a regular and fixed pattern.

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• 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.

• Tensile

Pulling (strength or stress).

• Terminal distribution box

Distribution boxes, mostly containing connection strips for copper cables on the subscriber side. This is the last cable junction before the terminals.


• Termination

A connection.

• Tight Buffered Fibre

A fiber having a plastic buffer jacket applied directly over its protective coating.


• Tight-Buffered Cable

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.


• Time Division Multiplexing

Transmission method in which several digital signals arriving in parallel are transmitted as a serial data stream over the
same fibre.

• Topology

The physical layout of the network that describes how the system components are actually placed and connected to each other.
While the architecture is the logical view, the topology is a physical view of the network.

• 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.


• Transmission Bandwith

The frequency at which the magnitude of the transfer function of an optical fibre has fallen to a specified value. The transmission bandwidth of an optical fibre is approximately reciprocal to its length.


• Transmitter

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


• Triple Play Services

The offering, by carriers, of voice, video and data services over one edium (one network). Usually this reduces network complexity
and cost for the carrier and offers preferred pricing for subscribers.

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• Ultra Physical Contact Connector (UPC)

An optical connector whose end-face has been radiused and polished to minimize reflections. Unlike the APC connector, the
mating surfaces are NOT angled to the axis of the fibre. APCs provide superior reflectance performance compared to UPCs.

• Unshielded Twisted Pair (UTP)

Similar to the STP, but without the shielding metal layer. It is more prone to interference but is less bulky that the STP cables.

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• Very High Bit Rate DSL (VDSL)

A promising development for a DSL protocol running at up to 52 Mbps over short distances.


• Visible spectrum

The portion of the electromagnetic spectrum that can be seen by the unaided human eye.

• Voice Frequency (VF)

The part of the audio frequency range used to transmit voice sound (usually 300…3400 Hz). This band is used by the modem for its modulated signal.

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• Wavelength

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


• Wavelength Multiplexing

Transmission method in which several signals are transmitted simultaneously at different wavelengths over the same fibre.

• WDM-PON

Based on multiple optical wavelengths to increase the upstream and/or downstream bandwidth available to end users


• Wide Area Network (WAN)

A network which encompasses interconnectivity between devices over a wide geographic area.


• Window

A range of wavelengths within which a fiber best operates.


• Wire guide

Part of the distribution block with double wire guide channels. The wires inserted in the sides of the wire inlets are guided to the IDC contacts at the front.


• Wires pairs

wo wires (a, b) of a balanced-pair copper cable.


• 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 cords.

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• xDSL

A generic term for all varieties of DSL.

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• Zero-Dispersion Wavelength

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