Fiber Optics Glossary

A

 Absorption:  Decrease in signal strength in optical fiber as a result of the conversion of optical light to heat due to impurities in the fiber.

 APC:  Angled Physical Contact.  A fiber optic connector with an angled end used to lessen back reflection.

 Armor:  A protective coating or jacket for a fiber optic cable

 Attenuation:  A loss of signal strength within a fiber optic cable, usually expressed in dB.

 Attenuator:  A passive component designed to lessen signal strength while minimizing waveform distortion.

 B

 Backreflection (BR):  The scattering of optical power within a cable that is usually caused by a large change to the index of refraction between two points in the cable.

 Bandwidth:  The frequency range at which an optical fiber can transmit and receive data.

 Bend Loss:  Signal loss that is caused by bending an optical fiber cable beyond the manufacturer’s minimum recommended bend radius specification.

 Bend Radius:  The smallest practical radius that an optic fiber or cable can be bent prior to reaching an excessive level of attenuation.

 Bidirectional:  A fiber cable operating in both transmitting and receiving directions

 Buffer:  Any material that is used as a protective coating for a fiber optic cable.

 C

 C:  Celsius or Centigrade.  Used in manufacturers’ specifications for proper use and maintenance of a cabling environment.

 Cable :  A structure in which one or more fibers or wires is enclosed, typically with reinforcement and in a protective jacket.

 Cable Assembly:  A fiber optic cable that is terminated on both ends with any one of a number of optical connectors.

 Cable Plant:  All of the networking components that are used between the transmitter and the receiver of an optical system.

 Chromatic Dispersion:  A loss of bandwidth in a fiber optic cable that is caused by various wavelengths of light traveling at multiple speeds through the cable. 

 Cladding:  The specialized material that coats the core optical material in a fiber.  Cladding features a lower refraction index than the core optical material which causes the light signal to reflect inward and travel back into the core.

 Cleaving:  A special process by which an optical fiber is scored to produce a controlled breaking of the fiber which results in a flat and clean end that is close to perpendicular to the fiber axis.

 CWDM:  Coarse Wavelength Division Multiplexing.  This is the process of  piling 8 or less channels within the 1550 nm sector of an optical fiber.

 Coating:  The various materiala that surround the cladding of an optical fiber to protect it from environmental damage.

 Concatenation:  The process of linking multiple pieces of optical fiber.

 Concentricity:  The measured offset between the center of the optical fiber core and the center of its cladding in a fiber optic cable.  Or the measured offset between the center of the connector’s ferrule and the center of the connector’s hole in the ferrule.

 Connector:  A physical device that offers the connection and/or disconnection between two fibers or of the fiber and the source or detector).

 Core:  The inner section of an optical fiber that transmits the light signal.

 Coupler:  An optical component that either combines or splits a signal between optical fibers.

 D

 dB:  Decibel.  A logarithmic scale measurement unit of relative light power.

 dBm:  Decibels relative to milliwatt.

 Detector:  An optoelectric component that converts an optical signal into electrical current.

 Diameter mismatch loss:  Attenuation caused by splicing two different diameter optical fiber cores.  Loss is caused when a light signal is transmitted from the larger core into the smaller core.

 Dielectric:  A substance which does not conduct or transmit electrical current.

 Dispersion:  The spacing out of a light signal in an optical fiber that is caused by various speed light signals traveling through the fiber.  This is typically caused by either modal or chromatic effects in the fiber.

 DSF:  Dispersion Shifted Fiber.   This is a specific type of singlemode fiber that is designed to have near zero dispersion at 1550 nm.

 Dual Window Fiber:  This is special fiber that has been optimized to run more than one wavelength.

 Duplex Cable:  This is a cable that has been manufactured with two fibers that typically allows a fiber optic system to both transmit/receive optical signals.

 DWDM:  Dense Wavelength Division Multiplexing.  Transmitting multiple, tightly-spaced wavelengths in the 1550 nm region within a single optical fiber.

 E

 ESCON:   Enterprise Systems CONnection.  This is a virtually obsolete optical connector previously utilized for computer to computer data exchange.

 Ethernet:  This is a Networking Communication Protocol (IEEE 802.3) that has become the standard for using various transmission media, including LAN, WAN, and Internet.

 Excess Loss:  That portion of the light signal that does not make it through the fiber optic system.

 Extrinsic Loss:  Any loss in a fiber optic plant that is not caused by the fiber itself.

 F

 F:  Fahrenheit.   Used in manufacturers’ specifications for proper use and maintenance of a cabling environment.

 FC:  A standard type of fiber optic patch cable end connector. 

 FDDI:  Fiber Distributed Data Interface.  This is a type of fiber optical connection used in local area networking.

 Ferrule:  This is the component in a fiber optic connector that aligns and also acts as a terminator for the fiber optic patch cable.

 FTTC:  Fiber To The Curb.  This is the standard abbreviation used for the fiber optic service provided to a node that is connected by a coaxial cable to a neighborhood of nearby homes or buildings.

 FTTH:  Fiber To The Home.  This is the standard abbreviation used for the fiber optic service provided to a node located in a home or building.

 FOTP:  Fiber Optic Test Procedure.  This term refers to the standard procedures specified by the Electronic Industries Association (EIA) and used for testing fiber optic systems.

 Fresnel Reflection:  This refers to the Reflection loss at the end of a fiber optical cable that is caused by the difference in the index of refraction between glass and air.

 Fusion Splicer:  This is a special fiber optic instrument that bonds two optical fibers together via heat and pressure.

 G

 G:  Giga.  Mathematical prefix representing one billion, as in GigaHertz (one billion Hertz.)

 Ge:  Germanium.  A material often found in detectors and other electronic devices.

 GHz:  Gigahertz. This represents one billion cycles per second.

 Graded Index Fiber:  This is a  type of multimode fiber optic cable in which the refractive index of the core decreases parabolically as it nears the outer cladding.

 H

 Hertz:  A wave of one cycle per second.

 Hybrid Fiber Coax (HFC):  This is a hybrid cable with both fiber and copper wires used as media for data transmissions.

 HFC Network:  This is a data network that utilizes both fiber and copper cables.

 I

IEEE:  Institute of Electrical and Electronics Engineers.  This is a nonprofit association that provides standards for use within the Electrical and Electronics industries.

Index of Refraction:  The measured ratio of the speed of light in free space versus the speed of light in a fiber optic strand. 

InGaAsP:  Indium Gallium Arsenide Phosphide.  This is a material that is used in high performance fiber optic detectors.

Insertion Loss:  This is the loss of signal that results when a component (e.g., a connector) is inserted into a fiber optic cable pathway.

Interferometer:  This is a specialized instrument that is used to measure the endface geometry of a fiber optic connector.

Intrinsic Loss:  This is the loss of signal that occurs in spliced fibers due to differences in the types of fibers that have been spliced together.

J

 Jacket:  The protective outer covering of a fiber optic cable.

 Jumper:  A fiber optic cable assembly with connectors on both ends.  Also known as a Patch Cable.

 K

 kHz:  KiloHertz.  A signal measurement calculated at 1,000 cycles per second.

 km:  kilometer.  1,000 meters (1km=3280 ft)

 L

 LAN:  Local Area Network.  A data network that exists in a relatively small geographic area.

 Large Core Fiber:  A fiber optic strand with a core of 200 microns or more.

 Loose Tube:  A type of fiber optic cable in which the fiber strands are situated within a smaller subunit inside the cable’s jacket. 

 Loss:  Usually expressed in Decibels (dB). This refers to the amount of signal strength that is lost in a fiber optic cable via connectors, splices, the fiber itself, and other external influences.

 Loss Budget:  The overall attenuation in a system based upon all signal loss factors.

 M

 M:  Mega.  Mathematical expression for one million, as in MegaHertz.

 mA:  milliamp.   One one-thousandth of an Amp.

 Macrobend:   The macroscopic bending of a fiber from a straight line.  This can cause light to leak out from the fiber, causing attenuation.

 MAN:  Metropolitan Area Network.  This is used to signify a network that is larger than a LAN, including a series of connected LAN’s over a wider metropolitan area.

 Mass Splicing:  This refers to the splicing together of many optical fibers into a single unit.

 Mechanical Splice:  This refers to a specific fiber splicing application in which two optical fibers are joined together via mechanical means.

 MHz:  Megahertz.  This represents 1,000,000 Hertz  or 1,000,000 cycles per second.

 Microbend:  This refers to the mechanical stress placed on a fiber optic strand that causes signal loss.

 Minimum Bend Radius:  This refers to the  smallest radius that an optical cable can be bent orior to causing an increase in attenuation.

 MM:  Multimode.  A type of fiber optic cable which allows multiple signal waves to travel on it simultaneously.

 Mode:  The ability of an electromagnetic wave or signal to travel in a fiber.

 Mode Field Diameter:  This is the measurement of the distribution of optical signal strength in a  singlemode fiber.

 Mode Filter:  This is a device that eliminates higher-order modes from a fiber optic cable.

 Mode Stripper:  This is a specialized component that eliminates modes traveling in the cladding.

 Multimode (MM) Fiber:  This is an optical fiber that allows more than one signal to be transmitted simultaneously. 

 N

 Numerical Aperture:  This refers to the light-gathering ability of a fiber optic strand and reflects the largest angle of acceptance as measured against the fiber axis.  It may also refer to the spread of the light signal from the end of a fiber strand.

 O

 O/E:  Optical to Electrical Converter.  This is a component that is used to convert optical signals to electrical signals. 

 Optical Fiber:  A glass or plastic fiber that has the ability to act as a waveguide for light for the transmission of data.

 Optical Link Loss Budget:  This refers to maximum loss allowed in a fiber optic link before network performance suffers.

 Optical Power Meter:  This is an instrument that is used to measure the optical signal strength at the end of a fiber optic cable.

 Optical Return Loss:  This is the calculation of the ratio of optical power reflected from a device back to the light source  and is usually expressed in decibels.

 Optical Time Domain Reflectometer:  This is a specialized instrument that is used to measure both the loss and the reflections that occur in a fiber link.

 P

 PC:  This is a type of connector polish that allows fiber optic strand ends to contact the connector while reducing back reflection and insertion loss.

 Pigtail:  A length of fiber optic cabling with a connector on only one end.

 Planar Waveguide:  This refers to a waveguide that is made with a dielectric material.

 PLC:  Planar Lightwave Circuit.  This is a device that incorporates a planar waveguide.

 Plenum Cable (UL type OFNP):  This is a specially jacketed cable whose smoke and flammability characteristics meet building code requirements thereby allowing it to be run in areas where a fire hazard may exist.

 PON:  Passive Optical Network.  This refers to a network that features fiber optic cabling in either all or most of the network servicing the end user.

 Preform:  A manufacturer’s glass rod that has specific attributes so that optical fiber strands may be drawn from it.

 R

 Radiation-hardened Fiber:  This refers to a specialized type of fiber optic cablethat can recover most of performance capabilities after exposure to radiation.

 Rayleigh Scattering:  This refers to the scattering of light that is caused by small imperfections along the length of the fiber optic strands.

 Receiver:  This is a device that contains a detector and converts light signals to electrical signals.

 Ribbon Cable:  This is a specially manufactured cable in which multiple fibers are manufactured in a flat ribbon-like cable construction.

 S

 SAN (Storage Area Network):  This refers to one or more shared storage devices that are networked so that the storage device(s) is available to all servers on a WAN or LAN.

 SC:  A type of fiber optical cable connector.  The “SC” stands for “Subscription Channel”.

 Sheath:  This refers to the jacket or outer protective layer of the fiber optic patch cable.

 Si:  Silicon, a material used in certain multimode detectors.

 Simplex:  Single.

 Singlemode:  This refers to the type of optical fiber which only supports a single lightwave propagating through it.

 SMA:  An optical fiber connector component.that is mostly obsolete in modern networks.

 Splice:  This refers to the joining of two optical fibers for the purposes of providing a continuous waveguide for a fiber optic signal.

 Split Ratio:  This number specifies the actual calculation of power distribution within an optical coupler.

 ST:   A type of fiber optical cable connector. 

 Step-index Fiber:  This refers to a specific type of optical fiber which offers a consistent refractive index in the actual core of the fiber while also offering a significant decrease in refractive index in the cladding of the strand.

 Strength Member:  This is a physical element that is incorporated into a fiber optic cable structure to add tensile strength.

 T

 Throughput Loss:  The comparison of signal strength at the output port of a fiber optic coupler versus the power measured at the input port.

 Throughput Port:  The out put port in a fiber optic coupler..

 Tight Buffer:  The specialized material that surrounds and protects the optical fiber strand(s) in a fiber optic cable.

 Total Internal Reflection:  The phenomenon that occurs when the lightwave in an optical fiber core strikes the cladding at a larger angle than the critical angle specification.

 Transmitter:  An optical network component that converts electrical signals to optical signals.

 U

 Unidirectional:  The quality of only operating in a single direction.

 V

 V:  Abbreviation for Volt.

 W

 W:  Abbreviation for Watt.

 WAN:  Wide Area Network.  This refers to a data communications network that encompasses a broad geographic area.

 Waveguide:  This is a dielectric material in which the optical structure has an inner core with a higher index of refraction than the outer section, thereby guiding lightwaves through the inner core via the principle of total internal reflection.

 Wavelength Division Multiplexing:  This communications technique allows for the utilization of a single optical fiber strand to send several signals through the strand with each signal operating at different wavelengths.

 Wideband:  The quality of a device or network having a large bandwidth.

 Z

 Zipcord:  This refers to a situation in which two cables connected by their outer protective jackets so that they may be quickly and easily separated along part or all of their lengths by simply physically pulling them apart.

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