Optical fiber glossary


ADAPTER: Mechanical part for connecting two connectors with different standards; also referred to as an inter-series adapter (e.g. SC / ST).

ADSL (Asymmetric Digital Subscriber Line): High-speed data transmission over subscriber line technology. Transfer rates are asymmetrical, i.e. download speeds for data received by the subscriber are faster than those transmitted by them (e.g. 640/1500kbps).

ANCHORING CLAMP:  Component used to fix ADDS or Figure-8 optical fiber or copper cables aerially on a number of different support structures, including poles.

APC: Connector finish type. The optical fiber is polished at an 8° angle to yield return losses better than -60dB. Note: APC finishes are not compatible with PC or UPC finishes.

ATTENUATION or SIGNAL DROP-OFF: Signal drop-off between two points (e.g. due to connectors, splices, optical fiber lengths, faults, etc.). Fiber attenuation is expressed in dB/km (0dB = zero attenuation). Spectral losses are related to the wavelength used. Example: 3dB/km @ 850nm and 1dB/km @ 1300nm over the same fiber-optic cable.

ATTENUATOR: Component for reducing optical power by creating a loss.


BACKBONE CABLE: Cable used to connect distribution frames and sub- distribution frames together in cabling systems.

BACKBONE: The backbone of a computer network to which all the networks and sub-networks are connected.

BANDWIDTH: Optical fiber bandwidth is defined as the maximum transmission frequency in MHz at which transmitted signal attenuation is 3dB. The wider the bandwidth, the greater the capacity for high-speed transmission. Expressed in MHz.km or GHz.km. Depends on the transmission wavelength and the physical attributes of the fiber such as its core diameter, materials, etc.

BENDING RADIUS: The lowest bending radius an optical fiber or cable can be subjected to without damaging the optical fiber.

BOOT: Generally designates a protective mechanical component. Depending on the manufacturer, the term can be used to designate the rear part of a connector that slides onto the tube or cable and is held in place by a press-fitting or dimensional shrinkage technique (mechanical, thermal, etc.).

BREAKOUT: Type of cable in which patchcords (usually 2mm in diameter) are protected by a single jacket.


CFO: Cable Fan-Out, grips the cables and provides fiber fulfillment.

CLADDING: 125 µm silica cladding covering the fiber core to achieve a low refraction index.

CLEAVER: Tool for cleaving (i.e. squarely cutting) the optical fiber in preparation for splicing.

COATING: 250µm protective coating providing mechanical protection; usually made of plastic and applied directly to the optical fiber cladding during extrusion.

COAXIAL CABLE: Cable with a concentric structure and a central conductor (single or multistrand wire), and surrounded by dielectric material, conductor shielding and an insulated outer jacket. The shielding either comes as braid or metal foil.

CONCENTRATOR: Hardware for grouping transmission channels together. Generally refers to an Ethernet HUB or Token Ring MAU.

CONNECTOR: Optical connectors provide a non-destructive means of connecting and disconnecting one or more optical fibers (multi-fiber connectors) to/from one optical cable to another or an optical cable to/from a device. Generally comprised of two connectors and an adapter (or feedthrough).

CRIMPING: Operation used to fasten an optical connector to a cable or protective fiber tube.


DEAD ZONE: Measurement area close to the reflectometer where the signal is prone to interference caused by the return loss of the measuring device.

DECIBEL or dB: Unit for measuring optical power (dB=10log (power ratio)).

DETECTOR: Photodiode that converts light signals into electrical signals

DIELECTRIC: Does not conduct (or poorly conducts) electricity, but is nevertheless permeable to electrostatic forces.

DISPATCHING: Changing how upstream optical fibers fitted with connectors are assigned by connecting them to a connector panel linked to a downstream network.

DISPERSION: Temporary separation of the wavelength circulating in a component (different modes or propagation speeds).

DISTRIBUTION FRAME: Equipment used to bundle, dispatch and distribute optical cables in OCNs. Distribution frames are available in two formats, farms and distribution cabinets, and receive the local loop cable heads (transport heads) and the active equipment mirror heads (operator heads).

DISTRIBUTION: Type of cable in which several 900µm cladded fibers are surrounded by Kevlar and enveloped in a protective jacket.

DP (Distribution Point box): Location at which the connection between the subscribers’ optical fibers (in other words, those for which the building operator is responsible) and the optical fibers of the commercial operators is made. This connection can either be achieved by splicing or dispatching.

DROPPED PAIR: Wiring error that creates a false pair with two wires from different pairs.

DUPLEX: Term used to designate optical connectors or connectors with two optical channels (connectors with two ferrules, adapters that take two ferrules).

DWDM (Dense WDM or Wavelength Division Multiplexing): Optical multiplexing technique operating in the 1550nm range.


ETHERNET: Copper networks with bandwidths of 10 to 1000Mbps, as defined in the IEEE 802 standard.

EUROCLASSES: European Union materials fire resistance classification system. The five Euroclass requirement categories are more comprehensive than in the old French classification system and also encompass the smoke released and droplets projected.


FAN-OUT: Component or assembly providing mechanical protection continuity between tubes or cables containing several fibers and N number of tubes or cables protecting one or more fibers.

FDDI (Fiber Optic Distributed Data Interface): ISO standard. Ring network providing high-speed (100Mbs) data transfer over optical fiber.

FERRULE: Ceramic part located at the end of a connector that holds the fiber in place.

FIBER CORE: Central part of an optical fiber, generally made of silica, inside which the optical signal and data are propagated. Several diameters are available, depending on fiber type (e.g. 9µm for singlemode fibers and 50 or 62.5µm for multimode fibers).

FOTAG: FOTAG IEEE 802.8 tube/micro module and optical fiber color code providing marking and identification.

FRP: Fiber-Reinforced Plastic = fiber-reinforced polymer; composite materials comprising resin and fine fibers (fiberglass, aramid or carbon fibers); their excellent mechanical properties combine with their low density to make them an ideal replacement for metals.

FTTx, FIBER TO THE…: Subscriber distribution network architectures providing an optical fiber infrastructure from the Central Office to an endpoint at varying distances from the end subscriber, depending on type.

– FTTA (Fiber To The Antenna): Fiber to the antenna.

– FTTB (Fiber To The Building): Fiber to the foot of the building.

– FTTH (Fiber To The Home): Fiber to the end subscriber’s home.

– FTTO (Fiber To The Office): Fiber to the office.

FULL DUPLEX: Simultaneous transmission on two channels in both directions.

FUSION SPLICE: Splice obtained by joining the ends of two optical fibers using a heat source. Accurate positioning and correct alignment of the two optical fiber cores are critical to fusion splice quality and reducing attenuation to a minimum.

FUSION SPLICER: Electrical equipment used to fuse two optical fibers together using an electrical arc.


G652D: Although the basic singlemode optical fiber standard is G652, a number of variants have evolved from it. G652D fibers have the highest performance and are the most common in this family of fibers. Performance is defined in accordance with standard IEC 60793-2-50, type B.1.3.

G655: G655 fibers are shifted dispersion fibers with a zero-dispersion wavelength shifted to 1450nm. Also known as NZDS, or Non-Zero-Dispersion Shifted fiber, came about as a result of the use of DWDM long-haul networks that needed slight chromatic dispersion to prevent interaction between the wavelengths.

G657: Developed to respond to operators’ technical and financial requirements, G657 singlemode fiber has many benefits: low bending radius, flexibility and ease of installation, all very useful cabling attributes, especially inside buildings.

GIGABIT ETHERNET: Term used to describe a variety of technologies used to implement the Ethernet standard at data transfer rates of 1 gigabit per second (1000 megabits per second).Technology that enables data to be transferred at the rate of 1 gigabit per second over twisted pair copper cable.


HFC: Hybrid Fiber Coaxial transmission.

HIGH SPEED: High-speed networks are the preferred solution when marketing xDSL, cable and local radio or optical fiber access offers. Speeds range from 128 Kbps to several Mbps. Very-High-Speed networks also exist thanks to optical fiber and can reach speeds of several Gbps.

HUB: Star configuration hub for connecting several workstations to the network using twisted pair cables.


IMPEDANCE: In coaxial cables, this refers to the equivalent impedance; in alternating current, to the resistance. Measured in Ohms.

INDEX MATCHING GEL: Fluid with the same refraction index as the two fused fibers that reduces return and insertion losses.

INSERTION LOSS: Loss caused by adding components such as splices, connectors, etc. to the optical link.


LAN (Local Area Network): Local network – covering a few hundred meters to several kilometers. Sometimes referred to as an Enterprise LAN.

LASER: Light Amplification by Stimulated Emission of Radiation. Lasers are used as light sources for fiber-optic communications.

LAUNCH FIBER: Fiber length used for taking reflectometer readings, connected either side of the cable being tested. Used to overcome the dead zone (dazzling) caused by the light path created by the reflectometer’s power.

LED (Light Emitting Diode): Semiconductor light source that converts electrical signals into visible light or infrared radiation.

LSZH (Low Smoke Zero Halogen): Describes a cable’s jacket or type of plastic as not being prone to releasing toxic fumes when burning.


MAN (Metropolitan Area Network): Network with a distance between the two furthest points that can reach several dozen kilometers; used to connect the devices and departmental networks of large companies or campuses. Often employs fiber-optic technology.

MECHANICAL SPLICE: Creates a permanent connection between two centrally aligned fibers using mechanical techniques based principally on crimping.

MEDIA CONVERTER: Media converters enable two network segments using different physical media such as coaxial cables, twisted pair cables and singlemode or multimode optical fibers to communicate with each other. A highly practical solution, they are ideal for extending copper segments over optical fiber to distant buildings or rooms, for example.

MHZ and MBPS: MHz = millions of cycles per second – Mbps = millions of bits per second. There is no direct correlation between Mbs and MHz because the data can be coded using different models (Manchester, NRZI, MLT 3, etc.). 10Mbs Ethernet and Token Ring use Manchester coding which brings the MHz and Mbps values close together. 100Mbs Ethernet and ATM use MLT3 coding which makes the MHz value approximately 3 times greater than the Mbps value.

MODES: Paths certain light rays can take within a fiber.

MODULE [TUBE, JACKET, MICRO-MODULE]: Subassembly of cladded fibers forming part of a fiber-optic cable. The optical fibers contained in a fiber-optic cable can be grouped together within modules. For example, a 144-fiber cable might comprise 12 modules, each containing 12 optical fibers.

MULTIMODE: Optical fiber in which several beams of light rays (also known as modes) can be maintained. Multimode fibers are characterized by core diameters that can range from a few tens to a few hundred micrometers (multimode cores are either 50 or 62.5µm). They are used to connect up private networks with short cable runs. There are several types of multimode fiber such as OM1, OM2, OM3, OM4, etc.

MULTIPAIR CABLE: Consists of several twisted or untwisted pairs of copper wires.

MULTIPLEXER: Device that combines several wavelengths and transmits them over a single fiber and separates them at the other end.


NANOMETER: Unit used to measure wavelengths. 1nm = 0.000000001m

NETWORK: Interconnection of systems, terminals or data transmission equipment.

10BaseT / 100BaseT NETWORK: Network adopting the IEEE 802 standard. 3. Uses twisted pair cables.

NUMERICAL APERTURE: Value corresponding to the propensity of an optical fiber to collect the light and propagate it.


OCN – OPTICAL CONNECTION NODE: Fiber-optic network concentration point, where active and passive equipment is installed from which the commercial operator can activate access for their subscribers.

OF: Abbreviation for Optical Fiber.

OITD – Optical Indoor Termination Device: Passive element located in homes or technical rooms with restricted access, OITDs serve as test points and the line of demarcation of responsibility between the fiber-optic access network and the end client network.

OM1, OM2, OM3, OM4: Multimode optical fibers have a doped silica core with a gradually increasing refraction index approaching the center. There are 2 main families of multimode optical fibers: 50/125μm (OM2, OM3, OM4) fibers and 62.5/125μm (OM1) fibers. 62.5/125μm (OM1) and 50/125μm (OM2) index gradient multimode fibers meet the industry standards for local networks. The 50/125μm OM3 and OM4 fibers are mainly used for local broadband networks. By way of example, 50/125μm OM4 fiber is designed for 10Gb/s applications.

OPTICAL FIBER: Signal transmission medium using light pulses. Optical fibers are extremely thin and comprised of flexible plastic or silica.

OPTICAL POWER BUDGET: Difference between the emitter power and the receiver power.

OPTICAL POWER: Light power at the emitter.

OPTICAL REPEATER: Device that regenerates the signal between two fiber-optic segments. Used to increase the length and expand the topology of the network.

OTDR or OPTICAL REFLECTOMETER: Measuring device for performing detailed analyses of optical links and locating events, impurities or breaks in the optical fiber.

OTO: Optical Telecommunication Outlet, a generic name for OITD, and the fiber-optic entry point in the subscriber’s home.


P2P: Point to Point. This type of architecture requires a continuous fiber to be installed that is not shared between the OCN (Optical Connection Node) and the user. Each network termination is supplied with its own dedicated fiber. This technology has the advantage of allowing all the potentially available bandwidth on an optical fiber to be assigned to the subscriber.

PATCH PANEL: Container installed in a distribution cabinet or case and designed to provide optical fiber fulfillment, connection and dispatching, irrespective of the structure of the cable (indoor or outdoor cable, singlemode or multimode fibers, etc.). Designed to take storage, splice and splitter cassettes.

PATCHCORD: Optical cable or cord, with one or two optical fibers fitted with connectors at either end, and used for dispatching or connecting two points together.

PIGTAIL: Usually a 900 μm optical fiber, preconnectorized at one end and connected at the other by a splice; also known as a semi-patchcord.

PMD (Polarization Mode Dispersion): One of the physical phenomena inherent in optical fibers and other optical components that causes light pulses to disperse when traveling along an optical fiber. This phenomenon affects signal transmission.

POF: Plastic Optical Fiber.

POLISHING: Operations involved in preparing the optical contacts of fibers at the tip of the connector ferrule. Different abrasives using a variety of materials, sizes and shapes are recommended by different manufacturers. There are two distinct types of polishing: rough polishing and finish polishing.

POLYETHYLENE (PE): Sheathing material with excellent mechanical properties. HDPE refers to High Density Polyethylene.

PON (Passive Optical Network): Passive optical network characterized by a passive point-multipoint architecture (several users share the same fiber and there is no active equipment between the central office and the subscribers). There are various different PON standards, including GPON and EPON.

POWER METER: Device that measures link attenuation in dB.

PRECONNECTORIZED (CABLE): Cable in which all the fibers have fittings at either end (connectors, mechanical splices, etc.) that allow them to be connected directly to passive or active components.

PREFORM: Silica tube used for producing fibers.


REFRACTION INDEX: Ratio of the speed of light in a vacuum to that in the medium in question.

RET: Remote Electrical Tilt, copper interconnection cable linking the RRU to the antenna, allowing the signal orientation in particular to be controlled.

RETUBING SHEATH: Plastic sheath with a different diameter for re-tubing 250µm structure fibers.

RETURN LOSS: Ratio of the reflected power over the incidental reflection power, expressed in dB. Reflected power is linked to events that cause attenuation of wave propagation through lines (for example: mechanical splices, connector signal rejection, etc.). It is especially important to keep return losses to a minimum in singlemode networks.

RRU: Remote Radio Unit, remote radio transceiver forming part of a wireless network radio station system.


SFP: Small Form factor Pluggable. Media conversion modules used to provide switch and router equipment with optical connectivity.

SHIELDING: Protective cable covering that eliminates electromagnetic and radio interference.

SILICA: Material produced by melting sand and used as the basis for manufacturing optical fibers.

SIMPLEX: Characteristic of a fiber patchcord with only a single fiber or connector, as opposed to Duplex, which has two fibers or two connectors.

SINGLEMODE: Optical fiber in which only a single beam of light rays (also known as a mode) can be maintained. This is because singlemode cores are extremely thin and can only support one mode of propagation in the most direct way possible, namely along the axis of the fiber. Singlemode is used for long distances and/or higher speeds. There are several types of singlemode fiber such as G652D, G657, G655, etc.

SLEEVE: Central part of an adapter used to align the ferrules of the two connectors.

SOURCE: Laser or emitter creating an optical signal.

SPLICE PROTECTOR or SMOOVE: Heat-shrink tube with metal strip or dielectric armor for protecting the spliced fibers.

SPLICE: Connection between 2 single fibers known as strands to form a permanent link. Splices can either be accomplished by side-by-side mechanical splicing or by fusing 2 fibers together using a fusion splicer.

SPLICING TRAY: Box or patch panel component designed to accommodate a defined number of spliced fibers, with optional coiling facility.

SPLITTER: Passive device used in PON networks. When used in the downstream direction, splitters replicate the optical signal from a fiber and direct it towards a defined number of other fibers (referred to as 1 to 8 splitters, 1 to 4 splitters and so on). When used in the upstream direction, splitters combine the optical signals from several clients.

STRIPPING: Operation consisting of removing a fiber’s protective mechanical coating, usually by mechanical means (calibrated pliers).

SUSPENSION CLAMP: Component used to support aerial ADDS or Figure-8 optical fiber or copper cables at intermediate points between the anchoring clamps.

SWITCH: Enclosure with a given number of ports (4, 8, 16 or 24) used to connect devices. Its purpose is to interconnect two local network segments.


TOPOLOGY: Layout of a network’s constituent parts (computers, cables and other devices). Networks can use mesh, bus, ring and star topologies.


VDI: Voice-Data-Images.


WAN: Wide Area Network using operator services and media and covering an extremely wide geographical area that is not distance-limited and sits above MANs and LANs.

WAVELENGTH: Wave oscillation measurement. Defined as: The speed of the wave divided by its frequency. Wavelengths are represented by the symbol λ (Lambda) and expressed in units of length (μm or nm).