Abrasion Mark A flaw on an optical surface, as could be found on an improperly polished end for termination.

Absorption In an optical fibre, the loss of optical power resulting from conversion of that power into heat.

Acceptance Angle For optical fibre, the angle over which light entering the fibre core will be guided along the core rather than reflected off the surface or lost through the cladding.

ACR (Attenuation Crosstalk Ratio)  The difference between attenuation and crosstalk, measure in dB, at a given frequency.  An important characteristic in networking transmission to assure that the interference signals imposed on that same pair by crosstalk from the pairs.

ANSI (American National Standards Institute)  The coordinating body for voluntary standards groups within the US.  ANSI is a member of ISO.

Application  A system, with its associated transmission method, which is supported by telecommunications cabling.

Aramid Strength Member Yarn used in fibre optic cable to provide additional strength and support to the fibre bundle.  See Kevlar.

ATM (Asynchronous Transfer Mode)  A high speed packet switching technology used to transmit video, data, voice, etc. via a fixed packed (or cell).

Asynchronous Transmissiuon A mode of data transmission whereby each bit of information is generated separately with some stop/start code to indicate the interval between bit.

Attenuation Loss of signal power between points.  In cables, it is generally expressed in decibels (db) per unit length, usually 100 metres.  As ettenuation increases, signal power decreases.

Backbone Cabling Cable and connecting hardware that connects equipment rooms, telecommunications closets and entrance facilities. Backbone cabling can be intra- or inter-building.

Balun An impedance matching device that connects a balanced line (such as twisted pair cable) to an unablanaced line (such as coaxial cable).

Bandwidth The range of frequencies that can be used for transmitting information on a channel.  Bandwidth indicates the transmission-carrying capacity of a channel, therefore, the larger the bandwidth, the greater the amount of information that can pass through the circuit.

Baseband A method of communication in which a signal is trasmitted at its original frequency without being impressed on a carrier.  Ethernet is an example of a baseband network.

Baud Rate Measurement of data transmission speed, expressed in bits per second or bps.

Bayonet Coupling In fibre optics, a quick coupling device for plug and receptacle connection, designed to lock a connector into an adapter or receptacle, eg. ST®  Connector.

Bend Loss Signal loss that occurs due to beams of light escaping where the fibre is bent.

Bend Radius (Minimum) The smallest bend a cable can withstand before the transmission is affected.

Bit A binary digit, the smallest element of information in a binary system. A 1 or 0 of binary data.

Bit Rate  The number of bits of data transmitted over a phone line per second.

BNC A coaxial cable connector, used with Thin-wire (IOBase2) Ethernet networks.

BPS (Bits per second) A measure of speed in serial transmission.

Break Out A separation of discrete fibres from a bundle which terminates a fibre optic termination.

Bridge A devise that connectors and passes packets between two network segments.  Bridges operate at the data link layer (Layer 2) of the OSI reference mode.

Broadband A method of communication in which the signal is transmitted by being impressed on a higher-frequency carrier.

Buffer Coating In fibre optics, a layer of material applied in addition to the optical fibre coating, which provides protection from stress and handling.  There are two types of buffers, tight and loose.  In tight buffer constructions the material is extruded directly over the coated fibre.  In loose buffer constructions, the coated fibre "floats" within a buffer tube that is usually filled with a non-hygroscopic gel.

Building Entrance Facility A facility that provides all necessary mechanical and electrical services, and that complies with all relevant regulations for the entry of telecommunications cables into a building.

Bundle A group of individual fibres contained within a single jacket acting as one transmission channel.

Byte Term used to refer a series of consecutive binary digits that are operated upon as a unit, eg. a unit of 8 bits.

Cable An assembly of one or more cable units of the same type and category in an overall sheath (jacket cover). It may include an overall shield.

Cable Assembly A length of cable with connectors installed on one or both ends.

Cable Jacket The outermost protective covering applied over the internal cable elements of core, cladding, buffer and strength member.

Cabling A system of telecommunmications cables, cords, and connecting hardware that can support the connection of information technology equipment.

Campus A premises containing one or more buildings.

Campus Backbone Cable A cable that connects the campus distributor to the building distributor(s).  Campus backbone cables may also connect building distributors directly.

Campus Distributor The distributor from which the campus backbone cabling emanates.

CATV (Cable Television) A communication system where multiple channels or programming material are transmitted into homes using broadband coaxial cable.

Central Member The centre component of a cable.  It serves as an antibuckling element to resist temperature-induced stresses and is sometimes serves as a strength member.

Channel The end-to-end transmission path connecting any two pieces of application specific equipment.  Equipment and work area cables are included in the channel.

Chromatic Dispersion Different wavelengths travel along an optical medium at different speeds.  Wavelengths reach the end of the medium at different times, causing the light pulse to spread.  This is called chromatic dispersion and can be measured by the measure of travel time at different wavelengths.

Circuit A two-way communication path between electronic devices.

Cladding The low refractive index material that immediately surround the glass or plastic core of an optical fibre.  Optical cladding promotes total internal reflection for the propogation of light in a fibre.

Cleaving A means of breaking an unbuffered fibre to produce a clean, flat surface prior to splicing or terminating.

Coating A protective layer of material over the cladding of an optical fibre.

Coaxial Cable A cable with at least one transmission line consisting of two conductors, an inner conductor and an outer conductor, insulated from one another by a dielectric.

Communication Transmission of information.

Conduit A pipe or tubing that runs underground, from floor to floor, or along a floor or ceiling in which cables can be pulled or housed for cable protection.

Connector A device attached to the end of a fibre optic cable, receiver or light source that joins it with another device or fibre.

Core See Fibre Core.

Coupler A device whose purpose is to distribute optical power among two or more ports, or the concentrate optical power from two or more fibres into a single post.  Couplers may be active or passive.

Crimp Sleeve A hollow, metal cylinder that when crimped, holds the connector to the cable via the strength member of the cable.

Cross-connection A connection scheme between cabling runs, subsystems and equipment using patch cords or jumpers that attach to connecting hardware on each end.

Crossed Pair A wiring error in twisted pair cabling where a pair on cone connector of the cable is wired to a different pair on the other end of the cable.

Crosstalk In twisted pair cabling, the introduction of unwanted signals from a nearby communication pair.  Crosstalk performance is generally expressed in decibels (dB).

Cut-Off Wavelength The longest wavelength at which a single-mode fibre can transmit two modes.  At shorter wave-lengths the fibre fails to function as a single-mode fibre.

Data Communications The movement of encoded information by an electrical transmission system. The transmission of data from one point to another.

Data Rate The maximum number of bits of informaltion which can be transmitted per second, as in a data transmission line, and typically expressed as megabits per second (Mb/s).

Decibel (dB) The standard unit used to describe gain or loss and relative power levels.

Decibel/kilometre (dB/km) A unit of measurement for fibre optic attenuation.

Dielectric Non-metallic and therefore non-conductive.  Glass fibres are considered dielectric.

Dielectric Cable A non-conducting cable, such as fibre optic cable, that contains no metal.

Diode A device that allows a current to move in only one director, eg. Light Emitting Diodes (LEDs), laser diodes and photodiodes.

Dispersion The spreading of light pulses as they travel in a fibre - often used to refer to chromatic dispersion.

Distributor The term used for the functions of a collection of components (such as; patch panels, patch cords) used to connect cables.

Drain Wire In copper cabling, an uninsulated wire in contact with a shield throughout its length.  Used for teminating the shield.

Dual Window Fibre Any fibre that is manufactured to be used as two different wavelengths. eg. a single-mode fibre usable at 1300nm and I 550nm is said to be dual windowed.

Duples Characteristic of data transmission.  Either full or half duplex (simplex) where full permits simultaneous, two-way communiction and half means only one side can talk at once.  See Simplex.

Duplex (Two Position) Connectors (FDDI) Used as the physical connections between stations on the FDDI ring to connect fibre optic cables.  The connectors are polarised to prevent the transmitting and receive fibres from becoming inadvertently interchanged.

Duplex Fibre Cable A two-fibre cable suitable for duplex transmission.

Duplex Transmission Transmission in both directions, either one direction at a time (half duplex) or both directions simultaneously (full duplex).

EIA (Electronic Industries Association) A group that specifies electrical transmission standards.

Electromagnetic Interference (EMI) The interference in signal transmission or reception caused by the radiation of electrical and magnetic fields by other equipment or cabling (noise). Optical fibres neither emit or receive EMI due to their all-dielectric design.

Equipment Cable A cable connecting equipment to a distributor.

Equipment Room A room dedicated to housing distributors and applications specific equipment.

ESCON® (Enterprise Systems Connection Architecture) An IBM channel architecture that specifies a pair of fibre-optic cables, with either light-emitting diodes (LEDs) or lasers as transmitters, and a signalling rate of 200Mbps.

Ethernet A network of high-speed transmission cables and software.  Ethernet networks operate at 100Mbps using CSMA/CD (Carrier Sense Multiple Access with Collision Detection) to run over coaxial cable.

Fan-out Unit A device allowing multiple devices on a network to communicate using a single network attachment.

FDDI The Fibre Distributed Data Interface - an ANSI-defined standard speciying a 100Mbps token-passing network using fibre optic cable, with transmission distances of up to 2km.

FDDI II  The proposed ANSI standard to enhance FDDI.  FDDI II will provice isochronous transmission for connectionless data circuits and connection-oriented voice and video circuits.

Ferrule A component of a connector that holds fibre in place and aids in its alignment, usually cylindrical in shape with a hole through the centre.

Fibre Any filament or fibre, made of dielectric materials, that guides light.

Fibre Core The light carrying central transmission area of a fibre, defined by its high refractive index.  The core is normally in the centre of a fibre, bound by concentric cladding of lower refractive index.

Fibre Optics The technique of conveying light or images through optical fibres for communication or signalling.

Fibre Optic Cable A thin, flexible transmission medium capable of conducting modulated light transmission.  It consists of a core of glass or plastic surrounded by a protective cladding, strenghening material, and an outer jacket.  Signals are transmitted as light pulses, introduced into the fibre by a light transmitter.

Fibre Optic Connectors Connectors that are uysed to connect fibre cable to equipment and interconnect cables.

Floor Distributor The distributor used to connect between the horizontal cable and other cabling subsystems or equipment. (See Telecommunications Closet)

FrequencyThe number of cycles, measured in Hertz (HZ), of an alternating current signal per unit time.

Full Duplex See Duplex.

Fusion Splice A splice accomplished by the application of localised heat sufficient to fuse or melt the ends of two lengths of optical fibre, forming a continous single fibre.

Generic Cabling A structured telecommunications cabling system, capable of supporting a wide range of applications. Generic cabling can be installed without prior knowledge of the required applications. Applications specific hardware is not a part of generic cabling.

Gigabit One billion bits.

Gigaherts One billion Hertz (Hz)

Half Duplex See Simplex.

Hertz (Hz) The standard measure of frequency, equal to one cycle per second.  Also see MegaHertz.

Horizontal Cable A cable connecting the floor distributor to the telecommunications outlet(s) (usually the telecommunications closet).

Horizontal Cross-connect A cross-connect of horizontal cabling to other cabling, eg. horizontal, backbone, or equipment.

Hub Generally a term used to describe a device that serves as the centre of a network or cabling system.  File servers often act as the hub of a LAN.  Hubs are used for multiplexing, multi-port bridging functions, switching and test access.  They can be either passive or active and are not considered to be part of the cabling infrastructure.

Hybrid Cable A cable containing both fibre optic and copper components, bundled together with an overall sheath.

IEC (International Electrotechnical Commission) An industry group that writes and distributes standards on electrical products and components.

IEEE (Institure of Electrical and Electronic Engineers) A professional organisation that defines network standards, and the body responsible for many standards used in LANs.

Impedance The total opposition that a circuit offers to the flow of alternating current (AC) at a particular frequency.  It is a combination of resistance (R) and reactance (X) and is measured in ohms.

Insertion Loss The loss caused by the inclusion of a splice, connector or other such component in a system.

Interconnect A location at which equipment cables are terminated and connected to the cabling subsystems without using a patch cord or jumper.

Interface A point at which connections are made to the generic cabling.

Internet Term used to refer to the world's largest internetwork, connecting thousands of networks worldwide.

ISDN (Integrated Services Digital Network) A standard protocol for digital telecommunications transmissions.

ISO (International Standards Organisation) An independent international body formed to define standards for multi-vendor network communications.  Its seven-layer OSI reference model specifies how different vendor's products communicate with each other across a network.

ISO9000 A set of international quality-management standards defined by ISO.  The standards, which are not specific to any country, industry or product, allow companies to demonstrate that they have specific processes in place to maintain an efficient quality system.

Jacket See Cable Jacket.

Jumper A cable unit or cable element without connectors, used to make a connection on a cross-connect.

Jumper Wire An assembly of twisted-pairs without connectors on either end used to join telecommunications links at a cross-connect.

Kevlar A strong synthetic material used in cable strength members. The name is a trademark of the Dupont Company.

Keying A mechanical feature of a connector system, which guarantees correct orientation of a connection, or prevents the connection to a jack or optical fibre adapter of the same type intended for another purpose.

Kilobits per second (Kbps) 1,000 bits per second.

Kilobyte(KB) A standard measure of data used with memory and is equal to 1,024 bytes.

LAN (Local Area Network) A network covering a relatively small geographic area, such as a floor of a small building. Compared to WANs, LANs are usually characterised by relatively high data rates and low error rates.

LED A light-emitting diode.

Loose Tube Buffer See Buffer.

Link A telecommunications circuit or channel between any two telecommunications devices.  Cabling links include all cables and connecting hardware, and does not include equipment and work area cables.

Local Area Network See LAN.

Loose Tube Type of cable design whereby coated fibres are encased in buffer tubes offering excellent fibre protection and segregation.

Macrobending Visible bends often caused by exceeding suggested bend radius of a cable.

MAN (Metropolitan Area Network) A network that spans a metropolitan area.  Generally, a MAN spans a larger georgraphic area than a LAN but a smaller geographic area than a WAN.

Meterial Dispersion Pulse dispersion due to the variations in a material's refractive index as a function of wavelength.

Mechanical Splicing Joining two fibres together by mechanical means to enable a continuous signal.

Media The various physical environments through which transmission signals pass.  Common network media include twisted-pair, coaxial and fibre optic cable, plus open air.  Sometimes called physical media.

Megabaud (MBaud) One million baud.

Megabit (Mb) One million binary bits.

Megabits per second (Mbps) A measure of network bandwidth.

Megabyte (MB) A measure of computer memory that is euqal to approximately one million binary bytes (1,048,576).

MegaHertz (MHz) A unit of frequency that is equal to one million Herts (cycles per second)

Microbending Minute but severe bends in fibre that result in light displacement and increased loss.  Most microbending can be avoided by selection of buffer materials and proper cabling, handling and installation techniques.

MIcron (µm) One thousandth of a millimetre or one millionth of a metre. A micron can be used to specify the core diameter of fibre optics network cables.

Microsecond One-millionth of a second.

Modal Dispersion Pulse broadening arising from variations in the times that different modes take to travel through a multimode fibre.

Mode A lightpath through a fibre.

Mode Field Diametre In a single-mode fibre, the region in which light propogates is larger than the glass core diameter (ie. partly in the cladding). This mode field diameter is a measured value and often listed as a requirment in the fibre specifications.

Modular Jack A female telecommunications interface connector.

Modular Plug A male telecommunications interface connector.

Multimedia Applications that communicate information by more than one means.

Multimode Fibre A fibre that supports propagation of multiple ffrequencies of light.

Nanometre (nm) A unit of length denoting one-billionth of a metre.

Nanosecond (ns) A unit of time denoting one billionth of a second.

NEC (National Electric Code) Defines building flammatory requirements for indoor cables.

Near-end cross talk (NEXT) Signal crossover from one twisted pair to a neighbhouring twisted pair, measured at the same end of the cable from which the disturbing signal is transmistted.

Node A generic term used to refer to an entity that can access a network.

Noise Undesirable communications channel signals.

Ohm The standard unit of electrical resistance. One volt will cause one ampere of current to flow through one ohm of resistance.

Open Systems Interconnection (OSI) A collection of international protocol standards for data networking.

Optical Fibre Cable See Fibre Optic Cable.

OSI Reference Model A network architectural model consisting of seven layers, each specifying particular network functions.  The highest layer (the application layer) is closest to the user and the lowest layer (the physical layer) is closest to the media technology.  The lower two layers are implemented in hardware and software while the upper five layers are implemented in software.

Packet Switching A data communications technique in which data is transmitted by means of addressed packets and a transmission channel is occupied for the duration of transmission of the packet only.

Patch Cord/Lead A short length of cable with connectors on one or both ends, used to attach connection blocks, patch panels, etc. Can also be referred to as cable assemblies.

Patch Panel Connecting hardware that typically provides means to connect horizontal or backbone cables to an arrangement of fixed connectors that may be accessed using patch cords or equipment cords to form cross-connections or interconnections.  It facilitates administration for moves and changes.

Photodiode Diode used for the detection of optical energy and the conversion of this energy into electrical power.

Physical Layer Layer one of the OSI reference model; encodes, modulates and transmits data across physical links (ie. the transmission medium, such as fibre cable) on the network, and also defines the network's physical signalling characteristics.

Pigtail A short length of fibre cable with a permanently attached device, usually a connector, on one end.

Propagation Delay Time required for a signal to pass from the input to the output of a device.

Protocol A formal description of a set of rules and conventions that govern how devices exchange information.

Pulse Dispersion The spreading out of pulses as they travel along an optical fibre.

Reflection The change in the direction (or return) of waves striking a surface. For example, electromagnetic energy reflections can occur at an impedance mismatch in a transmission line, causing standing waves.

Refraction The bending of light as it passes through materials with different indices of refraction.

Repeater A device that receives and retransmits a signal.

Resistance The property of a conductor that determines the current produced by a given potential difference.  It impedes the flow of current and results in the dissipation of power as heat.  Resistance is measured in ohms.

Return Loss Noise or interference caused by impedance discontinuities along the transmission line at various frequencies.  Return loss is expressed in decibels (dB).

Riser Pathways for indoor cables that pass between floors.  It is normally a vertical shaft or space.

RJ45 Connector A modular connector used in UTP wiring.  The connector has eight conductors to accommodate four pairs of wires and has become the dominant connector used in Token Ring UTP installations.

Router An interface between two networks.  While routers are like bridges, they work differently. Routers provide more functionality than bridges, eg. they can find the best route between any two networks, even if there are several different networks in between.  Routers provide network management capabilities such as load balancing, partitioning of the nework, use statistics, communication priority, and troubleshooting tools that allow network managers to detect and correct problems even in a complex network of networks.  Given these capabilities, routers are often used in building-wide or enterprise-wide networks.

Routing The dynamic exchange of network interconnection and topology information among the systems on interconnected networks.

Sheath A common term for the collection of twisted pairs in a multipair cable.

Shield A metallic layer that surrounds insulated conductors in shielded cable.

Shielded Twisted Pair (STP) Cable that is both twisted by pairs and shielded.

Simplex Generally a communications system or device capable of transmission in one direction only.  See Duplex.

Simplex Fibre Cable A single fibre cable.

Single-mode Fibre An optical fibre that allows propagation of only one mode.

Source A light emitter, either in LED or laser diode, that when properly driven will produce information carrying optical signals.

Splice The physical joining of two or more copper wires or optical fibres to form a common connection.

Sweep-test Pertaining to cable, the frequency response is verified by generating an rf voltage whose frequency is swept repeatedly through a given frequency range at a rapid constant rate.  The cable response is observed on an oscilloscope.

Synchronous Transmission Transmission in which there is a constant time between successive bits, characters, or events.  The timin is achieved by the sharing of clocking, a transmission method in which the synchronising of characters is controlled by timing signals generated at the sending and receiving Stations (as opposed to start/stop communications). Because you don't have to add these bits, synchronous transmission of a message with take fewer bits (and therefore, less time) than an asynchronous transmission, but because precise clocks and careful timing are needed in synchronous transmission, its usually more expensive to set up.

TCP/IP (Transmission Control Protocol/Internet Protocol) A common network layer and transport layer data networking protocol.

Telecommunications The transmission and reception of electrical or optical signals by copper wire, optical fibre, or electromagnetic means.

Telecommunications Closet Space for maintaining telecommunications equipment, cross-connect cable and cable terminations.  The telecommunications closet is a recognised cross-connect point between the backbone and horizontal subsystems.

Telecommunications Outlet A fixed connecting device where the horizontal cable terminates.  The telecommunications outlet provides the interface to the work area cabling.

TIA (Telecommunications Industries Association) TIA creates telecommunications standards through the EIA organisation.

Tight Buffer See Buffer Coating

Topology The physical or logical layout of links and nodes in a network, ie. the arrangement of the system.  The most common distribution system topologies are the bus, ring and star.

Total Internal Reflection Reflection of light back into a material after reaching an interface with a material of a lower refractive index at an angle at or above the critical angle.  Total Internal Reflection occurs at the core cladding interface within a fibre.

Transition Point A location in the horizontal cabling where a change of cable form takes place; for example flat cable connects to round cable or cables with differing numbers of elements are joined.

Transport Layer The fourth layer of the OSI model of data communications.  High level quality control (error checking) and some alternate routing is done at this level.

Twisted Pair A pair of wires that are twisted together to minimise crosstalk, by cancelling the magnetic fields generated in each of the twisted wire.  This cable is typically made up of several twisted pairs of wires within a surrounding protective sheath.

Underwriters Laboratories (UL) A private testing laboratory concerned with electrical and fire hazards of equipment.

Unshielded Twisted Pair (UTP) Cable an electrically conducting cable comprising one or more twisted pairs, none of which is shielded.

Velocity of Propagation The transmission speed of electrical energy in a length of cable compared to speed in free space. Usually expressed as a percentage.

WAN See Wide Area Network.

Waveguide A conducting or dielectric structure, such as an optical fibre, that guides electormagnetic waves along its length.

Waveguide Dispersion In single-mode fibre, the part of chromatic dispersion that is due to the different speeds that light travels in the core and cladding.

Wavelength The physical distance covered by one cycle of wave - measured in nanometers (nm) or micrometers (mm)

Wide Area Network (WAN) Two or more local area networks (LANs) that are connected by microwave, satellite, telephone or other long distance signal transmission techniques.  WAN's are designed to serve large geographic distances.

Work Area A building space where the occupants interact with telecommunications terminal equipment.

Work Area Cable A cable used to connect the terminal equipment to the telecommunications outlet.