Industry Glossary

Click on a letter to view the terms and definitions:
A  B  C  D  E  F  G  H  I   J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z

— A —

APC Polishing

Angle Physical Contact / APC polish can add an angle of 8 degrees to flat polish. Using this technique, you can reduce back reflection to roughly 70 dB.


Caused by impurities in the fiber such as hydroxyl ions, the loss of power in the optical fiber from the conversion of optical power to heat.


The half angle of the cone where incident light is internally reflected by the fiber core. This is equal to Sin-1.

Active Branching Devices

An instrument that converts an optical input into two or more outputs with gain or innovation.

Adjustable Attenuator

An attenuator circuit that decreases the strength of the input signal step by step without signal distortion while sustaining constant hindrance match.

Angular Misalignment

Loss of optical power at a connector due to angular deviation at fiber end face.


A general term indicating a decrease in power from one point to another. In optical fibers, it is measured in decibels per kilometer at a specified wavelength.

Avalanche Photodiode (APD)

A general term that refers to the reduction in the strength of signal, occurring in both analog and digital.

Average Wavelength (l)

The average of two wavelengths where the crest optical power is half.


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—B —


The reflection of waves, particles or signals back to their original direction, due to scattering.


A range of frequencies in a specific band.

Bandwidth-Limited Operation

The condition in a fiber optic link where the bandwidth limits performance due to the signal being distorted.

Bend Loss

Propagation losses in a fiber due to bending the fiber around a curvature, a frequently encountered problem.


A high capacity transmission that allows for a large number of messages to be communicated simultaneously using a range of frequencies.

Buffer Coating

A protective coating applied directly to the fiber cladding, used for protective purposes.

Buffer Tube

A hard plastic tube that holds one or more fibers due to its diameter being several times the size of a fiber.


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—C —

Cable Assembly

A cable harness, also known as a wire harness that is used for the interconnection of multi and singlemode fiber optic cable systems.

Cable Bend Radius

The minimum radius one can bend a cable or housing without kicking it, which is measured by the inside curvature.

Center Wavelength (Laser)

The wavelength of an optical source that is considered to be the middle.

Center Wavelength (LED)

The nominal value operating wavelength that is considered to be the middle defined by a peak mode measurement where optical power resides.

Chromatic Dispersion

The spreading of a light pulse due to differences in refractive indices at which there are different wavelengths also.


An outer layer that surrounds the fiber core from inner corrosion.

Cladding Mode

A mode that is limited to cladding of an optical fiber due to the fact that cladding has a higher refractive index.


Cutting or splitting an optical fiber by a controlled fracture of glass to obtin the end of a fiber.


Covering that is applied to the surface of a fiber optic to protect it from weathering and corrosion,


A device that is used to join one fiber to another fiber, source, detector or other device.

Connector Plug

A device that is used to discontinue an optical conductor cable.

Connector Receptacle

The fixed part of a connection that is mounted on a panel, where the receptacles mate with plugs.

Connector Variation

The maximum dumber in dB of the difference in the loss of insertion between two optical connectors or better known as Optical Connector Variation.


The central part of an optical fiber that carries the light; it has a refraction index higher than surrounding cladding.

Core Eccentricity

The measurement of the placement of the center of the core, identical to the cladding center.

Core Ellipticity (non-circularity)

The measurement of the core departure from the roundness.


A device with multiple parts to deliver optical power.

Coupling Efficiency

The efficiency of transferring optical power between two components.

Coupling Ratio/Loss (CR, CL)

The ratio or loss of optical power from an output port to the total output port, represented by a percentage.

Critical Angle

The smallest angle of the fiber axis at which a ray can be reflected at the core or cladding interface.

Cut-off  Wavelength

The wavelength of a singlemode fiber where the fiber exhibits singlemode operations.


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—D —




Decibel represented to a milliwatt


Decibel represented to a microwatt


The standard logarithmic unit representing the ratio of two powers. In fiber optics, the ratio is power.


An optoelectronics transducer used in fiber optics that converts optical power to an electrical current, usually considered a photodiode.

Dichroic Filter

An optical fiber that transmits light selectively through wavelengths

Diffraction Grating

An array of equally spaced reflecting/transmitting lines that enhance the effects of diffraction to concentrate the diffracted light in different directions in regards to the spacing of the lines and by the wavelength of light.


See Near-end Crosstalk.


A term to explain a phenomena that cause broadcasting or spreading of light as it travels through an optical fiber. Model, material and waveguide are three different types.

Duplex Cable

A cable with two different fibers suitable for duplex transmission.

Duplex Transmission

Transmission in both directions, one at a time or two at the same time, considered half or full duplex.


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—E —

Excess Loss

The optic loss from a portion of light in a fiberoptic coupler, that does not emerge from operational ports of a device.

Extinction Ratio

The ratio of low or off optical power levels to a high power optical level when the station is transmitting a stream of Halt symbols.

Extrinsic Loss

A portion of loss in a fiber interconnection that is not intrinsic to the fiber but is related to the joining of fibers, which can be caused by the connector or splice.


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—F —


Fiber Distributed Data Interface.


A mechanical device that consists of a rigid tube, used to confine and align stripped ends of fibers.

Fiberoptic Attenuator

A device that is installed in a fiber optic transmission system to help lower the power in the signal, often used to create a maximum of optical power received by the photodector within limits of the optical receiver.

Fiberoptic Communication System

The exchange of modulated/unmodulated optical energy within optical fiber media which eliminates the same/different media

Fiberoptic Link

A combination of fiber optic spans and repeaters which then form a transmission path.


Dielectric material that advices the direction of light, known as waveguide

Fiberoptic Cable

A cable that consists of one or multiple optical fibers

Fiber Optic Test Procedure (FOPT)

Standards that was developed and published by the EIA under the EIA-R5-455 series of standards.

Flat Polishing

A polish on the endface that results in back reflection of 14 dB or 4%.



Fusion Splicing

A lasting joint developed by the application of localized heat that fuses/melts the ends of an optical fiber which then forms continuous single fibers.


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—G —

Graded-index Fiber

The core of an optical fiber that has a nonuniform index of refraction. The core consists of concentric rings of glass whose refractive ineices decrease from the center axis, which reduces model dispersion which then increases fiber bandwidth.


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—I —

Index of Refraction

The ration of velocity of light in an area of free space compared to the velocity of light in a specific material, always represented by n.

Index-Matching Material

Material that is used during optical interconnection which has a refractive index close the fiber core, reducing Fresnel reflections.

Insertion Loss

The loss of power from inserting a component into a previously continuous path, usually a connector or splice.


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— J —


Fiber optics which have connectors on both ends.


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— L —


A light source that produces monochromatic light through simulated emission.

Launch Angle

An angle that is represented between the growth direction of the incident light and the optical axis of the optical waveguide.

Launch Fiber

An optical fiber that is used to couple and condition light from another optical source into optical fiber. The launch fiber is then used to develop an equilibrium model in multimode fiber.


The portion of an electrode that is used for the visible spectrum reaching from the near ultraviolet region through the visible region and into the middle infrared region, 0.3 microns to about 30 microns.

Light-Emitting Diode (LED)

A semiconductor diode that voluntarily emits light from the pn device when onward current is applied.


Electromagnetic waves within optical frequencies. “Light” was originally just radiation visible to the human eye with wavelengths between 400 to 700 nm, but has become customary to refer to radiation in the spectral regions adjacent to visible light.


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— M —

Mechanical Splicing

When two fibers are joined by mechanical applications to create continuous signals.

Megahertz (Mhz)

A measurement of frequency that is represented to one million hertz.


Curvatures of the fiber which include axial displacement of micrometers and wavelengths of a few millimeters. These microbends tend to cause the loss of light and increase the diminishment of fiber.


Another word for micrometer, representing one millionth of a meter.

Misalignment Loss

When angular misalignment, lateral displacement or end separation causes the loss of power.

Modal Dispersion

Dispersion resulting from the different transit lengths of different propagating modes in a multimode optical fiber.


A distribution of electromagnetic energy that satisfies Maxwell’s equations and conditions, in guided wave propagation such as waveguides or optical fibers.

Mode Field Diameter (MFD)

The diameter of the optical energy of a singlemode fiber.

Mode Filter

A component that is used to erase high-order modes from fiber and simulate EMD.

Multimode Fiber

A type of optical fiber that assists more than one of the propagating modes.


When two or more signals are transmitted over one communications channel, including time division multiplexing and wavelength division multiplexing.


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— N —


A unit of measurement that represents a billionth of a meter.

Near-end Crosstalk

When an optical power reflects from another input part, back to another part.

Numeric Aperture (NA)

The lightgathering ability of a fiber which determines the highest angle to the fiber axis at which light will be accepted and cultivated through the fiber. NA=sinq where q is the specific angle, also used to represent the angular spread of light from the central axis.


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— O —


Original Equipment Manufacturer.

Optical Bandpass

The scope of optical wavelengths that can be transferred through a component.

Optical Channel Spacing

The wavelength scope of a specific channel.

Optical Channel Width

The visible wavelength scope of a specific channel.

Optical Fiber

Dielectric objects that assist light; optical waveguide.

Optical Isolator

A device that is used to restrict reflected and unwanted light.

Optical Return Loss (ORL)

The ratio of optical power represented by an element or an assembly of optical power incident on an element port when that element or assembly is shown a link or system.


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— P —

PC Polishing

When the physical contract polish develops a curved endface that powers the fibers in the mating connectors into contract, reducing back reflection to 40dB.

Passive Branching Device

A component that will divide optical input into two or more optical outputs.

Peak Wavelength

The wavelength where the optical power of source is at its highest.


An optoelectronic transducer. Example; a pin photodiode or avalanche photodiode.


The small length of fiber always attached to a device such as a source, detector, coupler or connector.

Pin Photodiode

A photodiode with a large intrinsic layer in between a p-type and n-type layer.


The route of electric field in the lightwave.


Equipment entity at the ends of the link.


When you fuse with low current to make sure the fiber end is clean, preceding fusion splicing.

Primary Coating

A plastic coating that is added to the cladding surface of a fiber during development to maintain the integrity of the outside surface.


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— S —

SPC Polishing

The super physical contract (SPC) cover that includes an extended polishing cycle for a better finish, which creates a back reflection as lower as 55 dB.


The highest optical power required to achieve a specific level of performance for a fiber optic receiver.

Signal-to-Noise Ration (SNR, S/N)

The ratio of the dominant mode power that is expressed in dB, to the power of the highest side mode of Ps.

Simplex Cable

A term that represents a single fiber cable.

Simplex Transmission

A one directed transmission.

Singlemode Fiber

An optical fiber that assists one mod of light propagation higher than the cutoff wavelength.


A LED or laser diode light emitter in a fiber optic link.

Spectral Width

The measurement of the extent of a spectrum. The width of wavelengths consists in the output at one half of the wavelength of peak power. Typical spectral widths range from 20 to 60 nm for an LED and 2 to 5 for laser diodes.

Splice Closure

A device that is used to arrange and protect splice trays.

Splice Tray

A container that is used to assemble and protect spliced fibers


The constant joining of fiber ends to similar fibers without using a connector.

Stabilized Light Source

LED or laser diode that releases light with a controlled and continuous spectral width, central wavelength and highest power with regard to time and temperature.

Star Coupler

fiberoptic coupler where power at any input port is released to all output ports.

Step-Index Fiber

A multimode or singlemode optical fiber where the core refractive index is uniform throughout so a sharp step in refractive index happens at the core-to-cladding interface, usually referred as multimode fiber.


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— T —

Tee Coupler

An optical coupler with three ports

Tight Buffer

A type of cable where each glass fiber is compactly buffered by a protective thermoplastic coating with a diameter of 900 microns. There is a high tensile strength that is achieved which then provides durability and ease of handling.

Transmission Loss

The loss encountered when transmission through a system.


A topology that consists of a hierarchy of master-slave connector’s admits a connector and other FDDE nodes.


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— U —

UPC Polishing

The ultra physical contract (UPC) coat includes an extra polishing cycle for a finer surface finish, which leads to back reflection as low as 55 dB.


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— W —

Wavelength-Division Multiplexers (WDMs)

Unresisting fiberoptic components that combine or separate optical channels.

Wavelength-Division Multiplexers

A transmission technique that separates optical channels, distinguished by wavelength, which are then multiplexed onto an optical fiber for transmission.

Wavelength Isolation

A Wavelength-Division Multiplexers concealment of a light signal in the aspired channel of unwanted channels.