The absorbing of light energy within an optical fiber because of natural impurities in the glass. Absorption and scattering arethe main cause of attenuation (signal loss) in an optical fiber.

Acceptance Angle

The acceptance angle of an optical fiber is the maximum incidence angle of a light ray which can be used for injecting light into a fiber core or wave guide.

Active Device

A device that requires a source of energy for its operation and has an output that is a function of present and past input signals. Examples includes controlled power supplies, transistors, LEDs, amplifiers, and transmitters.


A mechanical device planned to align fiber optic connectors. It includes the adaptor sleeve (adaptor sleeve also referred in this glossary) that holds the two ferrules together.

Adapter Sleeve

A mechanical fixture in the adapter body that aligns and holds two terminated fiber connectors. Adapter sleeve material is typically phosphor bronze, ceramic or polymer.

Add/Drop Multiplexer

A device that ensures or removes one or more optical channels to a signal passing through it.


A continuously variable signal, opposite of digital.

Aramid Yarn

An ingredient in optical fiber cable that provides support, protection and tensile strength. Also referred to as KEVLAR, which is a brand of aramid yarn.

Atm (Asynchronous Transfer Mode)

A network technology that switches optical and electronic signals that are broken into 53-byte cells


The loss of signal strength (optical power) during transmission between two points. It states the total loss of anoptical system, measured in decibels per kilometer (dB/km) at specific wavelengths.

Attenuation Coefficient 

Speciality of the attenuation of an optical fiber per unit length, in dB/km.


The center of an optical fiber.

Back Reflection

A percent of the transmitted signal represented back towards the source from a fiber-optic interface. Back reflection (optical return loss) Light reflected from the cleaved or polished end of a fiber caused by the difference of refractive indices of air and glass. Typically 4% of the incident light. Expressed in dB relative to incident power.

Backbone Cabling

A system of cabling that connects the equipment and telecommunications rooms.


A range of optical spectrum assigned based on optical amplifiers.
Six bands are specified: O (original), E (enhanced), S (short), C (conventional), L (long), and U (ultra).
These cover the optical spectrum from 1260 nm to 1675 nm.


The difference between the highest and the lowest frequencies of a transmission channel or path. Identifies the amount of data that can be sent through a given channel. The greater the bandwidth, the greater the information-carrying capacity.

The information-carrying capacity of an optical fiber. It is measured in MHz-km and GHz-km, as distance plays an important role.


The smallest radius an optical fiber or fiber cable can twist before excessive attenuation of breakage occurs.


Operating in both directions

Bi-Directional Transceiver

A device that sends information in one direction and receives information from the opposite direction. Works as Transmitter and Receiver.


Base two numbers with only two values (0 or 1).


An optical property of a material that causes the polarizations of light to travel at different speeds.


An electrical or optical pulse that carries information.

Bit Error Rate (Ber)

A measurement of transmission accuracy. It is a ratio of bits received in error versus bits sent.

Bit Error Rate Tester (Bert)

Test equipment that measures the bit error rate (BET) of digital transmission systems.

Bragg Scattering

A distribution of light that is caused by a change in the refractive index of a material.


A buffer is a type of component used to encapsulate one or more optical fibers for the purpose of providing such functions as mechanical isolation, protection from physical damage and fiber identification.

C Band

A range of wavelengths from 1530 to 1565 nm. In this region, erbium-doped amplifiers (EDFAs) have highest gain EDFA and optical bands.

Cable Assembly

An optical fiber cable that has connectors installed on one or both ends. Available to visit "pigtail" and "patch cord" in this glossary.


A communications path or the signal sent over that path. Through multiplexing several channels, voice channels can be transmitted over an optical channel.

Channel Spacing

The amount of bandwidth allotted to each channel.

Chirped Pulse

A pulse in which the wavelength changes through the duration of the pulse.

Chromatic Dispersion

The variation in the velocity of light (group velocity) as a function of wavelength. It causes pulses of a modulated laser source to broaden when traveling within the fiber, up to a point where pulses overlap and bit error rate increases. CD is a limiting factor in high-speed transmission and must be properly compensated, which implies proper testing.


The material surrounding the core of an optical fiber. The cladding has a lower refractive index (faster speed) in order to keep the light in the core. The cladding and core make up an optical waveguide.


The process of scoring and breaking the optical fiber end in order to end a connector.

Coarse Wavelength Division Multiplexing (Cwdm)

A WDM technology that spaces wavelengths widely apart.
Applies to greater separation of wavelengths than DWDM.
In the case of single-mode applications CWDM defines 20-nm separation from 1270nm to 1610nm, with 1470nm to 1610nm the most commonly used wavelengths. With multimode fibers, the wavelengths are 778, 800, 825 and 850 nm.


A protector layer applied over the fiber cladding during the drawing process to protect it from the environment.


A mechanical device used on a fiber to ensure a means for aligning, attaching and decoupling the fiber to a transmitter,receiver or other fiber. Commonly used connections include 568SC (Duplex SC), ST, FDDI, FC, D4 and Biconic.


The centre of the optical fiber through which light is transmitted it has
highly reflective.


A device that combines two or more fiber inputs into one fiber output or divides one fiber input into two or more fiberoutputs "directional coupler" in this glossary.


The transferring of light going into and coming out of a fiber. This term does not refer that a coupler is used.

Critical Angle

The maximum angle at which light can be effuse within a fiber. Since critical angle equals the ratio of the numerical aperture to the index of refraction of the fiber core.

Cutoff Wavelength

The shortest wavelength at which a singlemode fiber conveys only one mode. At shorter wavelengths, it transmits twoor more modes.

Dark Fiber

Fiber lines that are supplied without any electronic or optical signaling equipment in its path.

Dbµ (Decibels Microwatt)

A measurement of decibels (dB) at one milliwatt.

Dbm (Decibels Milliwatt)

A measurement of decibels (dB) at one microwatt.


A unit of measurement to express logarithmic differences of power level. It is used to express power gain in amplifiers or power loss in passive circuits or components. Expressed as dB. 


A material such as a glass fiber, which is not metallic and is not conductive.


The bending of light rays as they pass around corners or through holes smaller than their own wavelengths.

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.

Diode Laser

Which is also laser diode that you can find in this glossary

Directional Coupler

A fiber-optic coupler that preferably transmits light in one direction.


Type of chromatic dispersion. Chromatic dispersion is the pulse spreading that arises because the velocity of light through a fiber depends on its wavelength.


The spreading or broadening of light pulses as they travel through a fiber. The fiber property that causes this effect is also called dispersion. The three principal types are modal dispersion, chromatic dispersion (CD) and polarization mode dispersion. (PMD)

Dispersion Compensation

Reducing dispersion in a fiber in order to reduce total dispersion. Different methods are used for chromatic dispersionand polarization mode dispersion.

Dispersion-Shifted Fiber

An optical fiber that has lower chromatic dispersion in the 1550 nm range.

Duplex Cord

A two-fiber cable used for bi-directional transmission.

Duplex Transmission

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

Dwdm (Dense Wdm)

DWDM and WDM are used synonymously.

Edfa (Erbium-Doped Fiber Amplifier)

An optical amplifier that boosts all channels in the optical signal at the same time.

Edwa (Erbium-Doped Waveguide Amplifier)

An optical amplifier similar to an EDFA, but derives a higher gain through a small waveguide rather than several metersof fiber.

Electro-Absorption Modulator

A semiconductor diode that modulates light from a separate laser, but that may be fabricated on the same wafer. Turning current on causes light absorption.

Emı (Electromagnetic İnterference)

The interference in signal transmission or reception resulting from radiation of electrical or magnetic fields. Opticalfibers are not susceptible to EMI.


A cabinet used to organize and enclose cable terminations and splices for use within main equipment rooms, entrancefacilities, main or intermediate cross-connects and telecommunications closets.

End Finish

Surface condition at the optical conductor face.


A thermosetting resin used to secure the fiber with the connector ferrule.


A passive filter that uses a Fabry-Perot cavity.


A data communications protocol originally enhanced for premises and local access networks operating at speeds from 10 Mbps to 10 Gbps. It was originally enhanced for peer-to-peer communications using shared media over relatively short distances. Ethernet features variable length packets that allow data to be sent with less overhead.

Evanescent Waves

The light that passes into the cladding from the core.

Excess Loss

The amount of light lost in a coupler, beyond that essential in the splitting to multiple output fibers.

Extrinsic Loss

Loss caused by imperfect alignment of fibers in a connector or splice such as lateral offset, angular misalignment, end separation, and end finish. Generally synonymous with insertion loss.

Extrinsic Ratio

The ratio of the low or OFF optical power level to the high or ON optical power level.

Fabry-Perot (FP)

A standard laser diode consisting of a semiconductor cleaved on each end forming a resonant chamber to create the lasing effect. Used in digital applications.


The rigid prong in a fiber-optic plug that aligns the fiber with the socket. Ferrule materials are ceramic, plastic and stainless steel.


A thin filament of glass or plastic consisting of a core (inner region) and a cladding (outer region) and a protectivecoating.

Fiber Bragg Grating (FBG)

A piece of photorefractive fiber that is exposed to high-intensity ultraviolet interference patterns that will cause it to reflect a specific wavelength while being transparent to all other wavelengths. Used in WDM systems.

Fiber Laser

An alternate way of building a laser. The laser is built into the fiber itself.

Fiber Optics

Information transmitted through optical fibers in the form of light.

Fiber Sensör

A sensing device in which the active sensing element is an optical element attached directly to an optical fiber. The measured quantity changes the optical properties of the fiber so that it can be detected and measured.

Fiber To The Building/Business (FTTB)

A topological reference to a PON network that supports multiple subscribers in a single structure (a business or a building)

Fiber To The Curb/Customer (FTTC)

Distribution of communication services by ensuring fiber-optic links to a central point in each neighborhood and continuing to the homes by either twisted pair or coax.

Fiber To The Desk (FTTD)

Transmission system using fiber-optics as the medium throughout, from transmitter to desktop.

Fiber To The Home (FTTH)

The distribution of communications services by providing fiber-optic links all the way into each house.

Fusion Splice

The joining of two fiber ends by applying enough heat to fuse or melt the ends together to form a continuous single fiber.

Fusion Splicer

Fusion Splicer that permanently bonds two fibers together by heating and fusing them.

Graded-İndex Fiber

Graded Index fiber is other type of optical fiber in which the refractive index of the core is non-uniform. This non-uniformity is present because the refractive index is higher at the axis of the core and continuously reduces with the radial movement away from the axis.



A measurement instrument which projects interference bands across the face of fiber-optic connector. The bands are used to determine the centering, angle of apex offset and radius of curvature of the fiber-optic connector.


A fiber-optic component that either permits only unidirectional passing of light or that passes only some wavelengths of light.

İndex Of Refraction

Measure of the bending of a ray of light when passing from one medium to another.


A range of light from approximately 700 to 1000 nm. Fiber-optic systems transmit between 700 and 1700 nm.

Injection Loss-Insertion Loss

Total optical power loss caused by the insertion of an optical component such as a connector, splice or coupler into a previously continuous path. (Measured in dB)


The combination of light waves in which the wave amplitudes add together. Constructive interference produces brightlight when the peaks are in phase with each other. Disruptive interference produces dark zones when the peaks of one wave align with the valley of the second.

Intrinsic Loss

The loss due to inherent traits within the fiber; for example, absorption (light energy is absorbed in the glass) and spliceloss (mismatched numerical aperture).


L Band

A range of wavelengths from 1565 to 1625 nm. In this region, erbium-doped amplifiers (EDFAs) can be used, but haveless gain than in C band


Light Amplification by Stimulated Emission of Radiation; a coherent source of light with a narrow spectral width. DFB, Fabry-Perot and VCSEL are the three types of lasers used in fiber-optic communication systems.

Launch Cable

A known good fiber optic jumper cable attached to a source and calibrated for output power used used as a reference cable for loss testing. This cable has to be made of fiber and connectors of a matching type to the cables to be tested.

Laser Diode

A laser made of semiconductor materials widely used to transmit light into optical fibers. It is always used for single mode fiber and certain high-bandwidth multimode fiber such as used with Gigabit Ethernet.

Led (Light Emitting Diode)

A semiconductor device that emits incoherent light formed by the P-N junction.

Local Areas Network (LAN)

An interconnected system of separate stations, usually computers, in one relatively small geographical location such as a building or complex.

Long Wavelenght

A commonly-used term for light in the 1300/1310 and 1550 nm ranges.

Loose Tube

The protective tube surrounding one or more fibers. This is usually found in cables used for outdoor installations.



The loss due to large scale bending (extrinsic loss). Bending causes imperfect guiding of light which will exceed thecritical angle of reflection. Macrobending loss can be reversed once the bend is corrected.

Material Dispersion

Caused by variances in the speed of light at different wavelengths. Material dispersion and waveguide dispersion make up chromatic dispersion.

Mechanical Splice

Joining two fiber ends together by a temporary or permanent mechanical method in order to maintain continuous signaltransmission.

Mems (Microelectromechanical Systems)

Tiny components etched from a semiconductor material that can move under the control of electronic signals. MEMSdevices include movable mirrors that can switch or redirect the path of light.


The loss of light due to small distortions in the fiber, not usually visible to the naked eye.

Microbending Loss

In an optical fiber, loss caused by sharp curvatures involving local axial displacements of a few micrometers and spatial wavelengths of a few millimeters. Such bends may result from fiber coating, cabling, packaging, installation etc

Micron (µm)

One micrometer or one millionth of a meter. Used to express the geometric dimension of fibers.

Modal Dispersion

The spreading of light pulses along the length of the fiber caused by differential optical paths taken in multimode fiber.See


A reflective path that the light takes in a fiber. Each mode has its own pattern of electromagnetic fields as it spread through the fiber. There is only one mode in singlemode fiber. In multimode fiber, multiple modes are generated, causing pulse dispersion at the receiving end

Mode Field Diameter

In singlemode fiber, the diameter of the zone where the single mode propagates down the center of the fiber. It is larger than the core diameter.


An optical fiber in which light travels in multiple modes. Multimode fiber is used in shorter-distance applications than single mode fiber


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



A unit of measure , 10-9 m, used to measure the wavelength of light.


A system of cables, hardware and equipment used for communications.


Oc-1, Oc-3, Oc-12, Oc-48, Oc-192, Oc-786

An optical carrier rate in the SONET hierarchy

Oeo (Optical Electrical Optical)

Devices that convert light back to electricity for manipulation and then back out to light. Contrast with OOO.

Ofnp (Optical Fiber Non-Conductive Plenum)

A type of fiber-optic cable.

Ofnr (Optical Fiber Non-Conductive Riser)

A type of fiber-optic cable.

Ooo (Optical Optical Optical)

Devices that maintain the transmission signal as light throughout. Contrast with OEO.

Optical Amplifier

A device that boosts signals in an optical fiber. The EDFA was the first successful optical amplifier

Optical Channel

A signal transmitted at one wavelength in a fiber-optic system.

Optical Network

A network that processes and switches signals in optical form.

Optical Switch

A device that routes optical signals to their appropriate destination. All-optical switches (OOO) do not have to convertlight back to electricity for processing

Optical Waveguide

An optical fiber, planar waveguide or other structure that guides light along its length.

Otdr (Optical Time Domain Reflectometer)

An instrument that measures optical transmission characteristics by sending a short pulse of light down a fiber andobserving backscattered light. Used to measure fiber attenuation and evaluate optical transmission at splices andconnectors.


Passive Optical Network

A fiber-optic system with no active components between its distribution point and remote receiver nodes.

Patch Cord

A specific length of optical fiber cable with terminated connectors on each end. Used for connecting patch panels for optoelectronic devices.

Pc (Physical Contacting)

A type of fiber-optic connector that causes two terminated fiber ends to contact each other, keeping signal losses to aminimum.


A device that receives optical power and changes it to electrical power


Having to do with light or photons.


A short length of fiber in which one end is attached to a component and the other is free to be spliced to another fiber.

Planar Waveguide

A flat waveguide on the surface of a substrate with a lower refractive index. It confines light similar to an optical fiber. Used in waveguide arrays.


The alignment of the perpendicular electrical-magnetic fields that make up a light wave.

Polarization Mode Dispersion

The dispersion that arises from slight asymmetries in optical fibers. The speed of light varies with polarization.

Polishing Paper

Also known as lapping film, it is a paper with a fine grit used to remove any imperfections in the fiber end surface that may exist after cleaving. Fiber ends terminated within a connector are polished flush with the end of the ferrule.

Polishing Puck

A device used to hold the connector during the polishing of the fiber.

Population İnversion

The state of atoms that have been excited.


Raman Amplifier

A device that boosts the signal in an optical fiber by transferring energy from a powerful pump beam to a weaker signalbeam.

Receiver (Rx)

 A device containing a photodiode and signal conditioning circuitry that converts light to an electrical signal in fiber optic links.


The process that occurs when a light ray traveling in one material hits a different material and reflects back into the original material without loss of light.


The bending of light rays as they pass through a transmission medium of one refractive index into a medium with adifferent refractive index.

Refractive İndex

The ratio of the velocity of light in a vacuum to the velocity of light in a specific material. Using 1.0 as the base reference, the higher the number, the slower light travels.


A device that takes a fiber optic signal and regenerates it for retransmission, used in very long fiber optic links.


A pathway for indoor cables that pass between floors.


S Band

A range of wavelengths from 1460 to 1530 nm


The change of direction of light after striking small particles that causes loss in optical fibers.

Single Mode

 A fiber with a small core, only a few times the wavelength of light transmitted, that only allows one mode of light to propagate. Commonly used with laser sources for high speed, long distance links. It typically has an 8-10 µm core within a 125 µmcladding


A laser pulse that retains its shape in a fiber over long distances

Sonet (Synchronous Optical Network)

A scale of standard data rates for fiber-optic systems used in North American systems.


A device that provides for a connection between two fibers, typically intended to be permanent.

Splice Closure

A container used to hold and protect splice trays.

Splice Tray

A container used to hold, organize and protect spliced fibers.

Split Sleeve

The part of a fiber-optic adapter that aligns the ferrules of two terminated connectors.


A device that takes the light from one fiber and injects it into the cores of several other fibers.

Step-İndex Fiber

A fiber in which the core and cladding each have a uniform, but different, refractive index


Threshold Current

The least current required to cause a diode laser to generate a beam of light.

Tight Buffer

A protective coating (typically 900 µm) that is extruded directly over the primary coating of fibers. Provides high tensilestrength, durability, ease of handling and termination.


A transmitter and receiver combined in one device.

Transmitter (Tx)

An optoelectronic device which converts an electrical signal to an optical signal. It is usually an LED or laser diode.

Transparent Network

A fiber-optic network that is entirely light based with optical switches and other optical-only devices.

Tunable Laser

A laser that can change its frequency over a given range.


Vcsel (Vertical Cavity Surface-Emitting Laser)

Pronounced "vixel." A semiconductor laser that emits a beam from its surface rather than its edge

Voa (Variable Optical Attenuator)

A device that can be adjusted to block different fractions of light passing through it.



A structure that guides electromagnetic waves. An optical fiber is an optical waveguide.

Waveguide Array

A device that separates wavelengths by passing them through an array of curved waveguides running between a pair of mixing regions.


The length of a wave measured from any point on one wave to the corresponding point on the next. The wavelengths oflight used in optical fibers are measured in nanometers. Common wavelengths are 850, 1300 and 1350 nm.

Wdm (Wavelength Division Multiplexing)

Transmitting several wavelengths of light (colors) in one fiber

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