Extron Glossary of Terms
Fiber Optics


Absorption - The attenuation of light as it passes through fiber, similar to the resistive loss of an electrical signal as it passes through cable. Absorption is caused by impurities and defects in the fiber.

Acceptance Angle - In fiber optics, this is the critical angle, measured from the center axis of the fiber. Incoming light must be directed below this angle in order to enter the core of the fiber and propagate along its length through total internal reflection.

Aerial Cables - Optical fiber cables designed for outdoor installations on aerial supporting structures such as poles. They are specifically designed to withstand adverse conditions such as wind and ice loading, pollution, UV radiation, thermal cycling, stress, and aging.

Air Blown Fiber – ABF - Optical fiber installed through special tube cables by means of using pressurized air or nitrogen to "blow" bundles of fibers through individual tubes within the cable. Tube cables are usually preinstalled at the premises before installation of air blown fiber.

Air Polish - In fiber optics, this is the first step in polishing the connector using special fine grit film, after the fiber has been cleaved.

All Dielectric - In fiber optics, this denotes the presence of only dielectric, or non-metal elements.

Amplitude Modulation – AM - Amplitude modulation is also employed in fiber optics applications, in which light acts as a carrier signal with its amplitude varying in accordance to the signal being conveyed.

Anaerobic - For fiber optics, this describes a method of bonding between optical fibers via a non-heat, intrinsic chemical reaction within the adhesive material. By definition, an anaerobic adhesive does not require air to cure.

Angle of Incidence - The angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal

Angled Physical Contact – APC - A specific technique for singlemode fiber applications where the endface of the fiber or ferrule is cut and polished at an 8 degree angle in order to increase contact surface area and help minimize return loss. APC connectors are typically green in color and are not used in multimode applications. They are also rarely used in digital applications. APC polished connectors are not compatible with UPC, SPC, or PC polished connectors. Intermixing APC polished connectors with UPC/SPC/PC polished connectors can damage the fiber optic cable or equipment.

Aramid Yarn - A woven strength member, with Kevlar® as a common brand, incorporated into fiber optic cable that provides tensile strength and protection.

Arc - In fiber optics, the discharge that may occur between the two electrodes of a fusion splicer.

Attenuation - In fiber optics, this is the loss of optical power as light passes through a fiber optic path. This loss can occur due to absorption, scattering, and excessive bending within the fiber, and can also be attributed to optical components such as connectors, splices, and splitters. Attenuation is usually expressed in dB/km.

Avalanche Photodiode – APD - A type of photodiode, or optical signal transducer that converts light to an electrical signal, used in fiber optic receivers.

Backreflection - Light within an optical fiber that is reflected back toward the source. This typically occurs at interfaces between the fiber and the connector where an air gap causes the reflection.

Backscattering - The portion of light within an optical fiber that is scattered back toward the source.

Bend Loss - In fiber optics, the attenuation of light as it passes through a fiber with excessive bending. Macrobending and microbending both contribute to bend loss.

Bend radius - The smallest radius at which an optical fiber or fiber optic cable can be bent without introducing attenuation or damage to the fiber.

Bit Error Rate – BER - The fraction of bits that were transmitted with errors, expressed at the ratio of incorrectly to correctly transmitted bits. BER is used to assess transmission accuracy in a fiber optic system.

Bit Rate - The number of bits that are conveyed or processed per unit of time. The bit rate is quantified using the bits per second (bit/s or bps) unit, often in conjunction with an SI prefix such as kilo- (kbit/s or kbps), mega- (Mbit/s or Mbps), giga- (Gbit/s or Gbps).

Breakout Cable - In fiber optics, a cable comprising a bundle of several jacketed fibers, with the fibers separated from the bundle at one end to facilitate installation into panels and other equipment. The fibers are individually jacketed.

Breakout Kit - In fiber optics, a kit used to create a breakout cable from bundled fiber optic cable.

Buffer Coating - A plastic coating applied to an optical fiber that provides protection from moisture or damage, as well as handling during the manufacturing of fiber optic cable.

Buffer Tube - An additional plastic tubing around the buffer coating of an optical fiber that provides added protection. This tubing is typically colored.

Butt Closure - A product that serves to provide protection to fiber optic cable splices and terminations within a sealed enclosure.

Cable Jacket - The outer protective covering of wire or fiber optic cable.

Chromatic Dispersion – CD - In fiber optics, a factor that reduces fiber bandwidth as a result of the separation of the incoming light into components of various wavelengths, which travel at different speeds along the fiber. This effect is associated with singlemode fiber at very long distances.

Cladding - In fiber optics, the outer layer surrounding the core of a fiber that serves as an optical barrier as well as protection for the core. The index of refraction for the cladding is always lower than that for the core in order to maintain total internal reflection and thus ensure that the light always travels within the core.

Cleave and Crimp - In fiber optics, the utilization of pre-polished connectors to significantly reduce termination time by eliminating the most time consuming step – polishing the connectors, so that the process requires just cleaving the fiber, insertion into the connector, and crimping.

Cleave Tool - Also known as a scribe tool, this specialized tool is used to break off a portion of an optical fiber by scoring, or scribing the fiber so that it can be cut using a cleaver to ensure a clean, precise, cut with the endface flat and at a 90-degree angle to the fiber axis.

Cleaving - The process of cutting the end of an optical fiber after it has been scored, or scribed using a cleave or scribe tool. The cut is made at a precise 90 degree angle to the fiber axis.

Coarse Wavelength Division Multiplexing – CWDM - The multiplexing, or combining of several wavelengths into a single optical signal. CWDM is distinguished from Dense Wavelength Division Multiplexing – DWDM in that the separation between wavelengths – 20 nm – is much greater.

Coating - A layer of plastic covering over the fiber to provide protection from moisture as well as damage in manufacturing fiber optic cables. Also known as a buffer coating.

Compression - The art and science of reducing the amount of data required to represent a picture or a stream of pictures and sound before sending or storing it. Compression systems are designed to eliminate redundant or repeated information to the desired data level while allowing the original information to be reproduced to the desired quality.

Core - The central core of an optical fiber in which the light travels. The core’s index of refraction is always greater than that of the cladding which surrounds it, to maintain total internal reflection and therefore keep the light within the core.

Coupling Loss - The loss of optical power as light passes through a junction, expressed as the ratio of the optical power measured at the junction, such as a coupler, to the total optical power entering the system.

Critical Angle - An important angle of incidence for light as it meets a boundary between two refractive materials. Below this angle, total internal reflection occurs. In an optical fiber, light always strikes off the boundary between the core and cladding below the critical angle so that it is internally reflected within the core as it travels along the fiber.

Curing Oven - A specialized oven used to thermally cure epoxy for adhering a fiber optic connector ferrule onto the optical fiber.

Cutoff Wavelength - In singlemode optical fiber applications, the wavelength below which the fiber transmits as multimode instead of singlemode.

Dark Fiber - A term in fiber optics to denote fiber that is installed at a facility but reserved for future use.

Data Compression - A mathematical algorithm for compressing or encoding data to fit within given bandwidth requirements for transmission or storage.

Data Link - A fiber optic system comprising the cable, transmitter, and receiver for transmission of data between two locations.

dB (Decibel) - The standard unit used to express gain or loss of power between two values. A decibel is 10 times the logarithm of a ratio of two power values. When comparing voltage or pressure, the values in the ratio are squared or the log is multiplied by 20 instead of 10. An extension is placed behind the ‘dB’ when one of those values is a fixed reference (i.e. dBV, dBu, dBSPL).

dBm - dB referenced to 1 milliwatt. To convert into an equivalent voltage level, the impedance must be specified. For example, 0 dBm into 600 ohms gives an equivalent voltage level of 0.775V, or 0 dBu; however, 0 dBm into 50 ohms, for instance yields an equivalent voltage of 0.24 V. Since modern audio engineering is concerned with voltage levels, as opposed to power levels in the early years of telephone, the convention of using a reference level of 0 dBm is academic. But in the A/V industry, many people still refer to 0.775Vrms (600 r) as 0 dBm, which should be more accurately called 0dBu.

Dead Zone - A region within a fiber optic system where an OTDR – Optical Time Domain Reflectometer cannot effectively make measurements.

Dense Wavelength Division Multiplexing – DWDM - The multiplexing, or combining of several wavelengths into a single optical signal. DWDM is distinguished from Coarse Wavelength Division Multiplexing–CWDM in that the separation between wavelengths – 0.8 to 1.6 nm – is much smaller.

Detector - A device within fiber optic receivers that converts optical energy to electrical energy.

Differential Mode Delay – DMD - A limiting factor in the performance of transmissions over multimode fiber, in which there is a differential in the arrival times at the receiver of various wavelengths, or modes along the fiber. This differential is caused by model dispersion which is inherent in multimode fiber.

Dispersion - A limiting factor in optical fiber transmission performance, where a light pulse is broadened, or separated into modes or individual wavelengths. Dispersion limits transmission bandwidth and distance capability. The two major types of dispersion are modal dispersion and chromatic dispersion.

Dispersion Compensating Fiber – DCF - A special type of fiber designed to exhibit a large negative dispersion. DCF is typically used in long-haul telecommunication systems to compensate for dispersion in optical fiber.

Dispersion Shifted Fiber – DSF - A singlemode optical fiber with its optimal dispersion wavelength shifted, through the addition of dopants, to a wavelength that delivers optimal attenuation.

Distribution Cable - Fiber optic cable comprising a bundle of jacketed fibers encased within an outside jacket.

Distribution Panel - For fiber optic applications, this is both a patch panel and splice panel, usually installed at a hub or entrance facility

Dynamic range - The highest and lowest potential signal levels on a given device. Also applies to fiber optic applications in terms of the ratio between the most – or strongest – and least – or weakest – observable optical signals.

Effective modal bandwidth – EMB - In fiber optics, the modal bandwidth of a multimode fiber when using a laser as a light source. EMB is sometimes referred to as laser launch bandwidth.

Electrode - In a fusion splicer, the component which discharges electricity to enable two optical fibers to be fused or welded together.

End Finish - The endface of an optical fiber at the ferrule, finished or polished to be smooth in order to minimize signal loss or backreflection. PC, SPC, UPC, and APC polishing finishes are available for singlemode connectors.

Entrance Facility - In fiber optic applications, the entrance to a building for fiber optic cables.

Epoxy - An adhesive that bonds between surfaces by means of a chemical reaction in which the adhesive cures as it dries. Epoxy is used in fiber optic applications to adhere a connector ferrule to the fiber.

Extrinsic Joint Loss - The portion of optical signal loss at a joint that is not intrinsic to the optical fibers, usually caused by misalignment between the fibers, end separation, and imperfections in the end finish of either fiber.

Fabry-Perot – FP - A standard laser diode that uses a laser oscillator comprised of two mirrors with an amplifying medium between them.

Fan-Out Kit - In fiber optics, a kit designed for use with loose tube cable with bare fiber bundles in each buffer tube. The kit enables termination as well as protection of these bare fibers.

Fault - In fiber optics, any part of an optical fiber that deviates from normal performance.

Fault Finder - A simplified optical time domain reflectometer – OTDR, an instrument used to detect breaks within a run of optical fiber. Also known as a Fiber Break Locator.

Ferrule - A precision tube which centers an optical fiber and provides stabilization and precise alignment. A ferrule may be part of a connector or a mechanical splice.

Ferrule Connector – FC - A screw-type optical fiber connector that features a keying mechanism. FCs are typically designated as FC/PC, FC/SPC, or FC/APC to denote physical contact, super physical contact, or angled physical contact, respectively.

Fiber - The basic optical transmission element. The components of a fiber include the core, surrounded by the cladding, and then a coating for protection. Specific optical properties of the core and cladding enable light to be contained within the core as it travels along the fiber.

Fiber Break Locator - An instrument used as simplified method of locating breaks within an optical fiber. Also known as a Fault Finder.

Fiber Coating - A coating surrounding the cladding of an optical fiber during the draw process to protect the fiber from handling and the environment.

Fiber Distribution Unit – FDU - An enclosure that houses and organizes groups of optical fibers.

Fiber Optic Cable - A telecommunications cable comprising one or more optical fibers.

Fiber Optics - The transmission of light through optical fibers for telecommunications applications.

Fiber Surface Finish - A term describing or denoting the quality of the polishing at the end of a fiber.

Fiber to the Building/Business – FTTB - Fiber optic service to a business or building.

Fiber to the Curb – FTTC - Fiber optic service to a node within a residential neighborhood. The node in turn feeds several homes via copper wiring.

Fiber to the Desk – FTTD - Fiber optic runs to individual desktops.

Fiber to the Home – FTTH - Fiber optic service to individual homes.

Fibre Channel - An industry standard for connecting computers for gigabit-speed transmission over twisted pair and optical fiber at distances up to 10 km.

Figure 8 - In fiber optics, a method of polishing the end of a connector in a figure 8 pattern to minimize scratches.

Fillers - Non-conducting materials incorporated into the construction of a fiber optic cable to add roundness, flexibility, tensile strength, or a combination of all three.

Flat polish - In fiber optics, a condition at a ferrule where the endfaces of a fiber optic cable and the ferrule tip are polished flat.

FM - Frequency Modulation. A method of combining an information signal with a carrier signal so that it may be transmitted. FM radio is frequency modulated. Audio is encoded on the carrier by varying the frequency in response to the audio.

FOTS - Fiber Optic Transmission System.

Frequency Division Multiplexing – FDM - The combining of two or more signals into a single carrier signal for transmission through FM – frequency modulation. Each signal modulates the carrier signal at a different region of the frequency spectrum.

Fresnel reflection - The partial reflection of light that occurs at the boundary between two materials with different indexes of refraction. In fiber optics, this is considered a loss when light is partially reflected at a glass-air interface.

Fusion splicer - An instrument that is used to bond, or fuse two optical fibers together by heating, usually generated by a high intensity electrical arc.

Gain - (1) A general term for an increase in signal power or voltage produced by an amplifier. The amount of gain is usually expressed in decibels above a reference level. Opposite of attenuation. (2) The amplification of a signal, unit, or system. Expressed in the unit of measurement appropriate to the signal or system. (3) In fiber optics applications, the measurement of back reflections using an OTDR - Optical Time Domain Reflectometer, due to a mismatch in core sizes between adjoining optical fibers.

Gainer - In fiber optics applications, a backscatter measurement condition with an OTDR that indicates a splice loss, due to a mismatch in core size between the two optical fibers. The resulting trace indicates a perceived increase in power, and is therefore known as a “gainer.”

Graded index fiber - An optical fiber in which the index of refraction within the core of a multimode fiber decreases with the radius from the fiber axis. The index of refraction usually follows a parabolic profile from the fiber axis to the cladding, effectively addressing modal dispersion throughout the fiber link.

Graded Index Plastic Optical Fiber – GI-POF - A plastic multimode optical fiber with an index of refraction within the core that decreases from the fiber axis to the cladding. The index of refraction usually follows a parabolic profile from the fiber axis to the cladding, effectively addressing modal dispersion throughout the fiber link.

Index matching gel - A special gel with an index of refraction similar to that of the optical fiber core. It is applied at the fiber endface to minimize loss due to Fresnel reflection in mechanical splices or cleave and crimp connectors.

Index matching materials - Materials with an index of refraction similar to that of the optical fiber core. They are applied at the endfaces of adjoining optical fibers to minimize losses due to Fresnel reflection.

Index of refraction - The ratio of the speed of light in a vacuum to the speed of light in a material. Also known as the refractive index.

Injection Laser Diode – ILD - A laser in which the lasing, or stimulated emission of coherent light, occurs at the p-n junction of a semiconductor.

Inline splice closure - An enclosure which houses the spliced fiber optic cable and provides cable ports at opposite ends.

Innerduct - A duct, usually non-metallic, that may be placed within cable trays or HVAC ducts, to be used as conduit for installation of fiber optic cables.

Insertion loss - The loss of optical power as a result of incorporating components such as connectors, couplers, or splices into an optical fiber system.

Inspection scope - A microscope specifically for inspecting fiber optic connectors.

Interbuilding backbone - A backbone network that provides communication between buildings, such as on a university or corporate campus, or military installation.

Intermediate Cross-Connect – IC - A cross-connect, usually a patch panel, used to provide backbone cabling between the MC - Main Cross-Connect and HC - Horizontal Cross-Connect.

Intermediate Distribution Frame – IDF - In telecommunications applications, a metal rack, located in an equipment room or closet, that provides connection between interbuilding cabling and the intrabuilding cabling.

Intersymbol interference – ISI - In fiber optics, the interference between adjacent digital bits in a serial digital stream caused by pulse spreading in an optical fiber. Pulse spreading in an optical fiber due to dispersion in an optical fiber.

Intrabuilding backbone - The backbone network within a building that provides communications to individual offices and users.

Intrinsic Losses - Losses due to inherent differences in the characteristics of the optical fibers being spliced.

ITS - Intelligent Transportation Systems. Specialized systems that apply technology and intelligence to enable improved services in various modes of transportation and traffic management. Such systems make better information available, resulting in safer, more efficient use of transportation systems.

Jacket - Outer protective covering of a wire or cable.

Kevlar® - A brand name from DuPont for aramid yarn, used in the construction of cables to provide strength and strain relief.

Lapping film - Sheets of film used for polishing ferrule endfaces, comprising a film backing with mineral particles at various ratings for grit or coarseness.

Laser - Light Amplification by Stimulated Emission of Radiation. An optical source that generates coherent light within a narrow band of wavelengths.

Laser chirp - A sudden change in the center wavelength of a laser, caused by reflected or crosstalk optical energy entering the lasing chamber.

Laser-Optimized Multimode Fiber - A multimode fiber with higher bandwidth than legacy multimode fiber, designed for transmission with laser based sources such as VCSEL.

Light - The region of the electromagnetic spectrum that can be perceived by human vision, also known as the visible spectrum, which covers the wavelength range between about 0.4 µm to 0.7 µm. In laser and optical communications, this term denotes a broader portion of the electromagnetic spectrum, from the near-ultraviolet region of approximately 0.3 µm, through the visible region, and into the infrared region to 30 µm.

Light Emitting Diode – LED - A semiconductor device that emits incoherent, narrow-spectrum light within the p-n junction.

Light source - In fiber optics, a generic for the optical signal transmitter in an optical loss test set - OLTS.

Lightguide - Also known as an optical waveguide or optical fiber, a glass or plastic fiber with the ability to guide light along its axis. It comprises a core at the center, surrounded by a cladding with a lower refractive index to keep the light within the core through total internal reflection.

Link - An optical cable with connectors attached to the transmitter and receiver.

Loose buffer cable - A type of fiber optic cable in which the fiber is encased within a loosely surrounded buffer tube underneath the jacketing. The tube is usually for protection in outdoor installations.

Loose Tube Gel Filled – LTGF - A Loose Buffer Cable that is filled with a insulating gel material.

Loss - In fiber optics, the loss of optical power in connectors, splices, and fiber defects as light passes through a fiber optic system.

Loss Budget - A specified, maximum tolerable loss of optical power, or attenuation of light, as it passes through a fiber optic system.

Lucent Connector – LC - A high-density optical fiber connector becoming more popular and are replacing the popular SC due to the smaller size. LCs are used on Extron fiber optic products.

Macrobending - A term that describes a macroscopic deviation of an optical fiber’s axis from a straight line due to bending, to the extent that optical loss occurs.

Main Cross-Connect – MC - The central portion of a facility's backbone cabling that provides connectivity between equipment rooms, entrance facilities, horizontal cross-connects, and intermediate cross-connects. It usually consists of a distribution of patch panel.

Main Distribution Frame – MDF - A signal distribution frame that connects lines from the outside and lines on the inside.

Matched-Clad Optical Fiber - A singlemode optical fiber with a cladding of uniform refractive index, favored for being less susceptible to bending and splice losses.

Mechanical splice - A splice between optical fibers accomplished by using a mechanical fixture and an index gel, rather than by thermal fusion.

Messenger wire - A wire that is used as the supporting element of a suspended aerial cable. This wire may be an integral part of, or external to the cable.

Microbend - A localized defect in an optical fiber at the core-cladding boundary, caused by mechanical stress that results in sharp, microscopic curvatures in the fiber.

Microbending loss - Loss in an optical fiber due to sharp, microscopic curvatures, caused by imperfections in fiber coating, cabling, packaging, and installation, such as cinching fibers too tightly with a tie wrap.

Micron – μm - A micron, or a millionth (10-6) of a meter.

Mid-Entry - In fiber optics, the opening up of a fiber optic cable mid-span in order to access the fibers inside.

Military tactical cable - Heavy-duty cable designed for rugged installations in adverse environments.

Mini zipcord - A 2.5 mm diameter fiber optic cable with two jacketed fibers that can be separated.

Modal bandwidth - In fiber optics, the bandwidth-length product, measured in MHz-km, of an optical fiber due to modal dispersion.

Modal dispersion - In fiber optics, the dispersion of a single optical pulse into various modes which arrive at the light receiving device at different times. This limits the performance of multimode optical fiber.

Mode - A path for light within an optical fiber. Singlemode fiber comprises a single path, while in multimode fiber, there are multiple light paths.

Mode Field Diameter – MFD - A measure of the spot size or beam width of light propagating in a singlemode optical fiber. Usually this is 20% larger than the diameter of the core.

Mode filter - A device that removes higher-order modes in multimode fiber.

Multimode Fiber – MMF - An optical fiber that allows for the propagation of more than one mode or light path. It is commonly used with LED light sources for shorter distance links.

Multiple Termination Plug – MTP - A small form factor – SFF plug for multiple fibers.

Multi-Rate SDI - the capability to support multiple SMPTE serial digital interface standards, including SMPTE 424M (2.97 Gbps 3G-SDI), SMPTE 292M (1.485 Gbps HD-SDI), and SMPTE 259M (270 Mbps SDI).

Nanometer – nm - A nanometer, or one billionth (10-9) of a meter.

Numerical Aperture – NA - In fiber optics, the sine of the acceptance angle, a critically defined angle measurement from the center axis of the fiber. Incoming light must be directed below this angle in order to enter the core of the fiber and propagate along its length through total internal reflection.

NZDS - Non-Zero Dispersion Shifted fiber. A singlemode fiber with the zero-dispersion wavelength slightly beyond the spectral region for transmission in order to improve performance.

Optical Loss Test Set – OLTS - Test equipment for singlemode or multimode optical fiber comprising a light source and a power meter, used to measure optical signal loss along the fiber and any connectors in between.

Optical Return Loss – ORL - A measure, in dB, of the amount of optical power reflected within a fiber optic pathway due to the fiber and optical components.

Optical Time Domain Reflectometer – OTDR - An instrument in fiber optics used to measure backscattered light in the detection of defects along a span of optical fiber.

Output Power - In fiber optics, this is the radiant power, expressed in watts.

Overfilled Launch Condition – OFL - In fiber optics, a condition where the incoming light has a spot size and numerical aperture–NA larger than acceptable by the fiber. Typically associated with LED transmission and multimode cable.

Passive Optical Network – PON - A fiber optic network comprising singlemode fiber, passive splitters, and passive couplers for a service provider to deliver fiber to the home – FTTH, or fiber to the building – FTTB.

Photodetector - A device that senses incoming light and outputs an electrical signal in response to the light.

Photon - A elementary unit of light with both waveform and particle properties.

Physical Contact – PC - In fiber optics, the point at which a glass surface, such as that of a fiber, physically touches another glass surface, usually that of a connector. PC polished connectors can be used with SPC or UPC polished connectors but are not compatible with APC polished connectors. Intermixing APC polished connectors with UPC/SPC/PC polished connectors can damage the fiber optic cable or equipment. Multimode applications always use PC, SPC, or UPC polished connectors.

Physical plant - Infrastructure components including cable, connectors, splices, panels, splitters, repeaters and regenerators necessary to propagate the light signal between the transmitters and receivers of a fiber optic system.

Pigtail - A short length of cable with one end terminated with a connector and the other end spliced or hard-wired to existing cable or equipment.

Pigtail assembly - A short length of fiber optic cable with one end terminated with a connector, and the other end fixed to a transmitter, receiver, or long length of cable via a splice.

PIN Diode - Positive Intrinsic Diode. A type of photodiode, or optical signal transducer that converts light to an electrical signal, used in fiber optic receivers.

PIN-FET - Positive Intrinsic Negative Field Effect Transistor.

Pitting - In fiber optics, an undesirable endface polishing condition resulting from the use of lapping film that has been contaminated with fiber optic and grit particles. Pitting can also denote small cracks in the endface due to exposure of cleaning agents to intense light through a fiber.

Plastic Optical Fibers - Optical fibers in which the core and cladding are made of plastic. The diameter of the core is often larger than that of glass fiber.

Plug - In A/V and fiber optics, this is also known as the male connector.

Polishing paper - A plastic polishing sheet for optical fiber or connector endfaces with fine grit on one side.

Polishing puck - A fixture for optical fiber endface polishing, used to support a fiber optic connector ferrule in place, properly aligned to the lapping film.

Power meter - A device that measures the loss of optical power in a fiber optic connector, fiber optic cable, or fiber optic system.

Profile Alignment System – PAS - A technique for fusion splicing that employs a CCD camera for precisely aligning the cores of two optical fibers.

Pulse broadening - An increase in the duration of a pulse.

Pulse code modulation - A method used to convert an analog signal into noise-free digital data that can be stored and manipulated by computer. PCM takes an 8-bit sample of a 4kHz bandwidth 8000 times a second, which gives 16K of data per second.

Pulse spreading - The dispersion of an optical signal as it traverses along an optical fiber. Also known as Pulse Dispersion.

Pulse width - The time during which a source, such as a laser, is in an “on” state.

Receive – Rx - In fiber optics, to detect an optical signal from a fiber optic cable using a photodetector, such as a PIN diode, APD, or PIN-FET, and convert it to an electrical signal. The receive port of a transceiver.

Receiver - In fiber optics, this is the device at the receiving end of a fiber optic system that converts an optical signal to an electrical signal, and houses the necessary signal processing to output telecommunications, data, or A/V signals.

Receiver sensitivity - The minimum optical power necessary for the photodetector in a receiver to achieve a specified BER - Bit Error Rate or other performance specification such as signal-to-noise ratio.

Reflectance - In fiber optics, the ratio of optical power reflected to the incident power at a connector junction or other component or device. It is expressed as a negative value in decibels – dB.

Reflections - With video signals, reflections can be caused by energy that is not absorbed by the load (or a termination) and is reflected and possibly combined with the original signal. Reflected signals can occur when the impedance does not match (as a result of wrong termination or mixing of cable impedance). Some of the undesirable results of reflection include Y/C delays, color smearing, ringing on luma (but not on color), and ghosts. In fiber optics, abrupt changes in the direction of light at an interface between two dissimilar media so that the light returns to its origin.

Refraction - The change in direction of light as it passes from one medium to another, dissimilar medium. Refraction also occurs as light passes through a graded-index medium in which the refractive index varies within the medium.

Refractive index - Also known as the Index of Refraction, the ratio of the speed of light in a vacuum to the speed of light in a material.

Repeater/Regenerator - A repeater is a device that detects a weak signal and boosts its power for continued transmission. A regenerator receives a signal and regenerates or reconstructs its waveform for transmission.

Return loss - A measure of reflected energy in decibels at a specific frequency and cable length.

Ribbon cable - A cable with several copper wires or optical fibers, each jacketed side-by-side in a flat, ribbon-like structure.

Ribbon splice - The splicing of individual optical fibers of a ribbon cable, with each fiber spliced on a groove of a substrate or etched silicon chip. Each groove is spaced evenly and a flat cover holds the fibers in place on the substrate.

Ripcord - A cord of strong yarn, situated under the cable jacketing, used to facilitate in stripping and removal of the jacket.

Riser - A type of cable designed for vertical runs in shafts spanning multiple floors in a building.

Sag - A measure of the amount of sag in a fiber optic cable, taken at the midpoint of a span of cable between two points of support.

Sag section - A section defining a span of fiber optic cable between two points of support.

Sag span - A span selected within a sag section, used as a control to determine the proper sag, and therefore, tension of a fiber optic cable. At least two, and normally three sag spans in a sag section are required to sag a section properly.

Sag tension - The tension at which a fiber optic cable is designed to be installed.

Scattering - A source of optical signal loss in a fiber optic system, caused by the scattering of light due to small particles and other imperfections in the fiber.

Scribe - Scratching the surface of the fiber so that it can be precisely and cleanly cut at a right angle to the fiber axis.

Scribe tool - A device consisting of a scribing blade, usually made from diamond or tungsten carbide, used to scribe, or score a fiber to allow for a clean break and a smooth endface.

Service loop - A deliberately allotted slack of fiber optic cable, in a splice tray, closure, vault, or communications output, to accommodate future needs.

Sheath - Also known as a cable jacket, the outer protective covering of wire or fiber optic cable.

Signal to Noise ratio - Also stated as "S/N ratio". The ratio is expressed in decibels as a ratio between the audio or video signal level and that of the noise accompanying the signal. The higher the S/N ratio, the better the quality of the sound or picture.

Simplex cable - A cable comprising a single optical fiber.

Singlemode Fiber – SMF - An optical fiber with a small core, through which only a single mode can propagate.

Source - The optical source in a fiber optic system, usually an LED or laser diode.

Speed of light - 2.998 x 10e8 meters per second.

Splice - A permanent connection between the ends of two optical fibers by mechanically joining them together, or heating to fuse them together.

Splice closure - A housing designed to protect splices in a optical fiber from damage, sealing them from the external environment.

Splice organizer - A device that facilitates the splicing of optical fibers, as well as their permanent storage.

Splice panel - A rack or wall-mounted panel that allows fiber optic cables to be organized and spliced. The panel holds splice trays, cable routing, and slack storage.

Splice protector - In fiber optics, a device used to provide protection and mechanical strength to a fusion splice, so that it can be handled and organized into a splice tray or other storage.

Splice tray - A container that is used to secure, organize, and protect individual spliced optical fibers.

Stapler cleaver - A fiber optic cleaver that is shaped similar to a stapler.

Step index fiber - A fiber in which the refractive index is uniform throughout the core. On the other hand, for a graded index fiber, the refractive index of the core varies radially between the fiber axis and the cladding.

Straight Tip – ST - A popular legacy fiber optic connector with a twist lock design similar to a BNC. The ST connector has a 2.5 mm ferrule.

Stripper - A tool used to remove the jacket that surrounds a cable or an individual wire within the cable. In fiber optics, a stripper is used to remove the buffer coating from an optical fiber.

Subscriber Connector – SC - A popular fiber optic connector that features a snap (push-pull) coupling type. Being replaced by the LC in most applications.

Super Physical Contact – SPC - In fiber optics, a specific endface polish for a connector to achieve typically a -50 dB return loss in singlemode applications. SPC polished connectors can be used with PC or UPC polished connectors but are not compatible with APC polished connectors. Intermixing APC polished connectors with UPC/SPC/PC polished connectors can damage the fiber optic cable or equipment. Multimode applications always use PC, SPC, or UPC polished connectors.

Tap - A fiber optic coupler with two outputs, the second of which, part of the incoming light is tapped off into another fiber.

Tee coupler - A T-shaped fiber optic coupler with one input and two outputs.

Telecommunications closet - An enclosed, secure space for housing telecommunications equipment, cable terminations, and cross connects.

Termination - 1. A load or impedance at the end of a cable or signal line used to match the impedance of the equipment that generated the signal. The impedance absorbs signal energy to prevent signal reflections from going back toward the source. For video signals, termination impedance is typically 75 ohms; for sync signals, it is usually 510 ohms. 2. A connector at the end of a cable.

Termination Tools - Tools used in the preparation and installation of connectors on cables or optical fibers.

Terminator - A device that provides termination for a signal line or several signal lines at the end of a cable. Usually a close-tolerance resistor for each signal, a terminator is often mounted in its own enclosed connector, making it easy to install. In fiber optics, an optical plug used to fully terminate the optical path so no light is reflected back toward the source.

Tight buffered cable - A fiber optic cable for indoor use in which the buffer coating tightly surrounds the cladding for extra protection and provides color-coded identification.

Time division multiplexing – TDM - A digital transmission scheme where the channel is divided into two or more time slots or subchannels, such that the subchannels are taking turns in the bit stream. Multiple digital signals are multiplexed into a serial digital stream. The serial digital stream is transmitted to the receiver where it is de-multiplexed into the individual digital signals

Total internal reflection - The total reflection of light as it reaches a boundary between two optical media at an angle of incidence greater than the critical angle.

Transceiver - A device that can operate as a transmitter, receiver, or both.

Transmit – Tx - In fiber optics, the light source, such as an LED or laser.

Transmitter - A device that converts from one signal type to another for transmission.

Tunable Laser - A laser in which its central wavelength can be varied or optimized as desired for a particular application.

Ultra Physical Contact – UPC - In fiber optics, a specific endface polish for a connector to achieve typically a -60 dB return loss in singlemode applications. UPC has become the most common polish for fiber optic connectors in digital applications. UPC polished connectors can be used with PC or SPC polished connectors but are not compatible with APC polished connectors. Intermixing APC polished connectors with UPC/SPC/PC polished connectors can damage the fiber optic cable or equipment. Multimode applications always use PC, SPC, or UPC polished connectors.

Underfilled Launch Condition – ULC - In fiber optics, a condition where the incoming light only fills a small percentage of the fiber core.

Vault - A storage product that houses fiber optic cable slack and splice trays.

VCSEL - Vertical Cavity Surface Emission Laser. A high speed, low cost laser diode that emits perpendicular to the surface of the chip, rather than from an edge.

Visible Light - The region of the electromagnetic spectrum that is visible to the human eye, from 380 to 770 nm.

Waveguide Dispersion - The distortion of an electromagnetic signal, or in the case of fiber optics, light as it encounters a waveguide and is dispersed into multiple components of different modes or wavelengths.

Wavelength - The distance from one peak to the next between identical points in adjacent waves of electromagnetic signals propagated in space or along a wire. Wavelength is usually specified in meters, centimeters, or millimeters. In the case of infrared, visible light, ultraviolet, and gamma radiation, the wavelength is usually specified in nanometers (10e-9 meter) or Angstroms (10e-10 meter). Wavelength is inversely related to frequency. The higher the frequency of the signal, the shorter the wavelength.

Wavelength Division Multiplexing – WDM - The combination of two or more optical signals at different wavelengths for transmission within a single optical fiber.

White light - A blend of multiple colors of the visible portion of electromagnetic spectrum, resulting in light that is white in color to the human eye.

Zipcord - A cable comprising two jacketed wires or optical fibers that are conjoined together and can be separated.