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Fiber Optic Glossary

10BASE-2: A thin-coaxial-cable version of an IEEE 802.3 network.

10BASE-5: A thin-coaxial-cable version of an IEEE 802.3 network, very similar to the original Ethernet specification.

10BASE-F: A fiber-optic version of an IEE 802.3 network.

10BASE-FB: That portion of 10BASE-F that defines the requirements for a fiber backbone.

10BASE-FL: That portion of 10BASE-F that defines a fiber-optic link between a concentrator and station.

10BASE-FP: That portion of 10BASE-F that defines a passive star coupler.

10BASE-T: A twisted-pair cable version of an IEEE 802.3 network.

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ACCEPTABLE ANGLE: The half-angle of the cone within which incident light is totally internally reflected by the fiber core. It is equal to arcsin.

ATTENUATION: Loss of signal power between points. In fiber cables attenuation is a ratio of input power vs. output power, measured in decibels per unit length, usually dB/km.

ATTENUATION COEFFICIENT: A factor expressing optical power loss per unit of length, expressed in dB/Km.

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BACKBONE: A high-speed transmission system used to connect relatively distant points. Backbone fiber cable networks can be used to join autonomous networks within buildings or between different buildings.

BACKSCATTERING: The return of a portion of scattered light to the input and of a fiber; the scattering of light in the direction opposite to its original propagation.

BANDWIDTH: The information carrying capacity of a fiber cable. The bandwidth for a given wavelength is the lowest frequency at which optical power has decreased by 3 dB and is expressed in MHz¡Ákm.

BEND RADIUS: The radius of curvature that a fiber optic cable can bend without causing harmful effects on the optical or mechanical performance of the fiber cable.

BER: Bit-error rate.

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

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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 chromatic dispersion is expressed in picoseconds (of dispersion) per kilometre (of length) per nanometre (of source bandwidth). It is the sum of material and waveguide dispersion.

CLADDING: The layer of material, usually glass, that immediately surrounds the fiber cable core. The cladding is usually coated with another material to provide protection when handling.

CLEAVE: The process of cutting an optical fiber by a controlled fracture of the glass, for the purpose of obtaining a fiber end, which is flat, smooth, and perpendicular to the fiber axis.

COATING: A material applied to the cladding for protective purposes.

CONCENTRICITY: In a wire or cable, the measurement of the location of the centre of the conductor with respect to the geometric centre of the circular insulation.

CORE: The central part of the glass construction of the fiber through which light is transmitted.

CORE ECCENTRICITY: A measure of the displacement of the centre of the core relative to the cladding centre.

COUPLER: A multiport device used to distribute optical power.

CRITICAL ANGLE: The smallest angle at which a meridional ray may be totally reflected within a fiber at the core-cladding interface.

CUT-OFF WAVELENGTH: The wavelength at which a singlemode fiber transmits a single mode of light.

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DB: Decibel.

DBm: Decibel referenced to a milliwatt.

DECIBEL (dB): The standard unit used to express gain or loss of optical power. A standard logarithmic unit for the ratio of two powers, voltages or currents. In fiber optics, the ratio is power. dB = 10 log10 (P1)/(P2)

DIELECTRIC: Nonmettalic. All-dielectric designs are inherently nonconductive; all-dielectric fiber cables contain no metal and are lightning resistant.

DIFFRACTION GRATING: An array of fine, parallel, equally spaced reflecting or transmitting lines that mutually enhance the effects of diffraction to concentrate the diffracted light in a few directions determined by the spacing of the lines and by the wavelength of the light.

DISPERSION: The cause of bandwidth limitations in a fiber. Dispersion causes a broadening of input pulses along the length of the fiber. Two major types are: mode dispersion caused by differential optical path lengths in a multimode fiber cable and material dispersion caused by a differential delay of various wavelengths of light in a waveguide material.

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EDFA: Erbium-doped fiber amplifier.

EIA: Electronic Industry Association.

EMI: Electromagnetic interference.

ESCON: An IBM channel control system based on fiber optics.

ETHERNET STANDARDS: Not all Ethernet and IEEE 802.3 standards are identical. In fact, in some instances, there are enough differences in Ethernet standards to cause major problems. In a network environment (such as Ethernet Version 1.0 and IEEE 802.3) nodes can coexist and communicate properly on a network but the important link is overall transceiver-to-node integrity.

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FIBER ATTENUATOR: This component is a passive device installed into a optical fiber system and helps to reduce the optical signal if needed.

FIBER CHANNEL: An industry-standard specification for computer channel communications over optical fiber and offering transmission speeds from 132 Mbaud to 1062 and transmission distances from 1 to 10 km.

FIBER DISTRIBUTED DATE INTERFACE (FDDI): An ANSI standard to ensure compatibility of components from different manufacturers.

FIBER ENCLOSURE-: This component is used to house, route and terminate fiber optic cable either by fusion splice or using fiber optic connectors. A fiber enclosure will normally be a box, tray or dome that can be mounted into an equipment rack or on a wall or installed into underground pits.

FIBER MEDIA CONVERTER: A fiber media converter is a device that will convert an optical fiber signal to another media normally copper.

FIBER OPTIC CABLE: This cable is made from extruded glass optical fiber and can transmit a vast amount of information along its glass core offering far greater speed and information carrying capacity (bandwidth) over traditional copper systems.

FIBER OPTIC CONNECTORS: Connectors terminate the end of a fiber optic cable and allows for a fast and reliable connection and disconnection between fiber cable and equipment. A fiber optic connector also aligns the fiber cores so light can pass without major optical loss.

FIBER OPTIC TEST EQUIPMENT: This equipment is used by installers for testing and commissioning optical fiber networks.

FIBER OPTICS: Light transmission through optical fibers for communication or signalling.

FIBER TO THE HOME: Is a generic term for any broadband network that uses optical fiber to replace all or part of the traditional copper component.

FOBOT: Abbreviation for fiber optic breakout tray and is used to house, route and terminate optical fiber cable.

FOIRL: Fiber-optic interrepeater link.

FREQUENCY: The number of cycles per unit of time, denoted by Hertz (Hz). 1 Hertz = 1 cycle per second.

FREQUENCY MODULATION: A method of transmission in which the carrier frequency varies in accordance with the signal.

FTTB: Fiber-to-the-building or Fiber-to-the-basement ¨C fiber cable reaches the boundary of the building, such as the basement in a multi-dwelling unit with the final connection to the individual living space being made via alternative technology.

FTTC: Fiber-to-the-cabinet or fiber-to-the-curb ¨C fiber cable is terminated in a street cabinet typically closer than 300m from the customer premises with the final connection being copper.

FTTH: Fiber-to-the-home ¨C fiber cable reaches the boundary of the living space such as a box on the outside wall of a home.

FTTH products: This is a generic term for products used to build a broadband network that uses optical fiber cable and technology to connect individual dwellings into a central location.

FTTN: Fiber-to-the-node - this is very similar to FTTC, but the street cabinet is further away from the user's premises which can be up to several kilometers away.

FTTP: Fiber-to-the premises - this term is used in several contexts: as a blanket term for both FTTH and FTTB, or where the fiber optic cable network includes both homes and small businesses.

FUSED COUPLER: A method of making a multimode or single-mode coupler by wrapping fibers together, heating them, and pulling them to form a central unified mass so that the light on any input fiber is coupled to all output fibers.

FUSION SPLICER: These high precision units will perform a permanent very low loss join of two fiber optic cores using a technology where the glass is fused or ¡®melted¡¯ together

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GRADED INDEX: core refractive index profile that varies with the radius of the core.

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HALOGENS: Chemicals from the halogen family (chlorine, fluorine, bromine) are typically compounded into plastic materials to improve the flame retardance. When the materials are exposed to a high heat source, halogen gases are released, limiting the spread of flames but potentially causing a health hazard.

HERTZ: The unit of frequency, in cycles per second.

HYPALON: A thermoset jacket material providing excellent abrasion and flex fatigue resistance; flame and oil resistance; and resistance to weather, ozone, and oxidizing chemicals. Ideal for industrial and petrochemical applications.

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INDEX OF REFRACTION (IOR): The ratio of the velacity of light in free space to the velocity of light in a given material. Symbolised by n.

INSERTION LOSS: Total optical power loss caused by insertion of an optical component such as a fiber optic connector, fusion splice, or coupler into a previously continuous path.

ISDN (INTEGRATED SERVICES DIGITAL NETWORK): ISDN is an international standard for transmitting digital information (text, sound, voice, data, video, etc.).

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JUMPER: Fiber optic cable that has fiber optic connectors terminated on both ends.

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KEVLAR: The trademark of the Dupont Company for aramid yarn used as strength members in fiber optic cable.

KPSI: Tensile strength in thousands of pounds per square inch.

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LAN: Local area network.

LASER: A device that produces monochromatic, coherent light through stimulated emission. Most lasers used in fiber optic communication are solid-state semiconductor devices.

LIGHT EMITTING DIODE (LED): A semiconductor device which emits incoherent light from a p-n junction.

LOOSE TUBE BUFFERING: A fiber cable construction in which the optical fiber is placed in a plastic tube having an inner diameter much larger than the fiber itself. The loose tube isolates the fiber from the exterior mechanical forces acting on the cushion. The space between the tube and the fiber is often filled with a gel to cushion the fiber and help prevent water penetration.

LOSS BUDGET: The total acceptable loss for a given system from transmitter to receiver. Includes fiber optic cable, fusion splices and fiber optic connectors.

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MACROBENDING: In an optical fiber, all macroscopic deviations of the fiber¡¯s axis from a straight line; distinguished from microbending.

MATERIAL DISPERSION: Pulse dispersion due to the variations in a material¡¯s refractive index as a function of wavelength.

MICROBENDING: Minute but severe bends in a fiber that result in light displacement and increased loss. Most microbending can be avoided by the correct selection of materials and proper fiber cable handling and installation techniques.

MODAL DISPERSION: Dispersion resulting from the different transit lengths of different propagation modes in a multimode fiber. MODE ¨C A path of light through a fiber.

MODE COUPLING: The transfer of energy between modes. In a fiber, mode coupling occurs until EMD is reached.

MODE FIELD DIAMETER (MFD): In singlemode fiber, the region in which the light transmitted is larger than the glass core diameter. This mode field diameter is a measure value and often listed as a requirement with core diameter in fiber specifications.

MODE FILTER: A device used to remove high-order modes from a fiber and thereby simulate EMD.

MULTIMODE FIBER: A type of optical fiber that supports more than one propagating mode.

MULTIPLEXING: The process by which two or more signals are transmitted over a single communications channel. Examples include time-division multiplexing and wavelength-division multiplexing.

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NEOPRENE: A rubber elastomer jacket material providing excellent cold temperature flexibility, abrasion resistance and flame retardance. Ideally suited for outdoor, field deployable fiber optic cable and repeated flexing applications.

NUMERICAL APERTURE (NA): The ¡°light-gathering ability¡± of a fiber, defining the maximum angle to the fiber axis at which light will be accepted and propagated through the fiber. NA = sin q, where q is the acceptance angle. NA is also used to describe the angular spread of light from a central axis, as in existing a fiber, emitting from a source, or entering detector.

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ODN: optical distribution network.

ONT: optical network terminals.

OPTICAL TIME DOMAIN REFLECTOMETRY (OTDR): A method of evaluating fiber optic cable networks based on detecting backscattered (reflected) light. Used to measure fiber attenuation, evaluate fusion splice and fiber optic connector loss and also to locate faults.

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PC: Physical Contact.

PCM: Pulse-coded modulation.

PHOTON: A quantum of electromagentic energy. A ¡°particle¡± of light.

PIGTAIL: A fiber optic cable that has a fiber optic connector on only one end.

PISTONING: The movement of a fiber axially in and out of a ferrule and, often caused by changes in temperature.

PLENUM CABLE: A fiber cable whose flammability and smoke characteristics allow it to be routed in a plenum area without being enclosed in a conduit.

POLYETHYLENE (PE): Tough, chemical and moisture resistant jacketing material, ideal for outdoor cable applications.

POLYURETHANE: A jacketing material used mostly for outdoor fiber optic cable applications. Provides excellent abrasion resistance and low temperature flexibility.

POLYVINYLCHLORIDE (PVC): Flame retardant jacketing material providing good mechanical protection, flexibility, and abrasion resistance. Ideally suited for indoor fiber cable applications.

PULSE SPREADING: The dispersion of an optical signal with time as it propagates through an optical fiber.

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REFRACTION: The bending of a beam of light at an interface between two dissimilar media or in a medium whose refractive index is a continuous function of position (graded-index medium).

REFRACTIVE INDEX: The ratio of the speed of light in a vacuum to the speed of light in a material. Also called Index of Refraction.

REPEATER: A device that receives, amplifies (and perhaps reshapes), and retransmits a signal. It is used to boost signal levels when the distance between repeaters is so great that the received signal would otherwise be too attenuated to be properly received.

RISER CABLE: Indoor fiber optic cable made especially for between floor applications.

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SIGNAL-TO-NOISE RATIO (SNR): The ratio of signal power to noise power.

SINGLEMODE FIBER: An optical fiber that supports only one mode of light propagation above the cutoff wavelength.

SPECTRAL WIDTH: A measure of the extend of a spectrum. For a source, the width of wavelengths contained in the output at one half of the wavelength of peak power. Typical spectral widths are 20 to 60 nm for an LED and 2 to 50 nm for laser diode.

SPLICE: An interconnection method for joining the ends of two optical fibers in a permanent or semipermanent fashion.

STEP INDEX: A refractive index profile characterised by a uniform refractive index within the core and a sharp decrease at the core-cladding interface.

STRENGTH MEMBER: That part of a fiber optic cable composed of aramid yarn, steel strands, or fiberglass filaments that increase the tensile strength of the fiber cable.

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TDM: Time-division multiplexing.

THERMOPLASTIC: A plastic jacketing material that softens when heated and becomes firm on cooling. Thermoplastics include PVC, PE, Polyurethane, and Nylon.

THERMOSET: A jacketing material where the molecules have been cross-linked (interlocked) through exposure to heat or irradiation. Once the material is ¡°set¡±, it cannot be softened or melted by re-heating. Thermosets include Neoprene and Hypalon.

TIGHT BUFFER: In tight buffer fiber optic cable construction the thermoplastic is extruded directly over the coated fiber, increasing the outside diameter to 900 micron (0.9mm), an industry standard.

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WAVEGUIDE DISPERSION: Dispersion caused by the fact that light travels at different speeds in the core and cladding of singlemode fibers.

WAVELENGTH: The distance between the same two points on adjacent waves, the time required for a wave to complete a single cycle.

WAVELENGTH-DIVISION MULTIPLEXING (WDM): A transmission technique by which separate optical channels, distinguished by wavelength, are multiplexed onto an optical fiber for transmission.

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ZERO DISPERSION: Wavelength in singlemode fibers, the wavelength at which the effects of chromatic dispersion and waveguide dispersion are lowest; thus providing the greatest information carrying capacity.

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