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Fiber Optic Glossary

1. Apex offset: Is the offset distance between the fiber core axis and the apex of the radius of curvature.
2. Attenuation: The decrease in signal strength along a fiber optic waveguide caused by absorption and scattering. Attenuation is usually expressed in dB/km.
3. Attenuator: 1) In electrical systems, a usually passive network for reducing the amplitude of a signal without appreciably distorting the waveform. 2) In optical systems, a passive device for reducing the amplitude of a signal without appreciably distorting the waveform.
4. AWG (Arrayed Waveguide Grating): A device, built with silicon planar lightwave circuits (PLC), that allows multiple wavelengths to be combined and separated in a dense wavelength-division multiplexing (DWDM) system.
5. Backreflection (BR): A term applied to any process in the cable plant that causes light to change directions in a fiber and return to the source. Occurs most often at connector interfaces where a glass-air interface causes a reflection.
6. Bending Loss: Attenuation caused by high-order modes radiating from the outside of a fiber optic waveguide which occur when the fiber is bent around a small radius. See also macrobending, microbending.
7. Bend Radius: The smallest radius an optical fiber or fiber cable can bend before excessive attenuation or breakage occurs.
8. Buffer: 1) In optical fiber, a protective coating applied directly to the fiber (illustrated). 2) A routine or storage used to compensate for a difference in rate of flow of data, or time of occurrence of events, when transferring data from one device to another.
9. Cable: One or more optical fibers enclosed, with strength members, in a protective covering.
10. Cable Assembly: A cable that is connector terminated and ready for installation.
11. Cable Plant: The cable plant consists of all the optical elements including fiber, connectors, splices, etc. between a transmitter and a receiver.
12. CATV: Originally an abbreviation for community antenna television; the term now typically refers to cable television.
13. Central Office (CO): A common carrier switching office in which users’ lines terminate. The nerve center of a communications system.
14. Channel: A communications path or the signal sent over that path. Through multiplexing several channels, voice channels can be transmitted over an optical channel.
15. Circulator: Passive three-port devices that couple light from Port 1 to 2 and Port 2 to 3 and have high isolation in other directions.
16. Cladding Mode: A mode confined to the cladding; a light ray that propagates in the cladding.
17. Cleave: The process of separating an optical fiber by a controlled fracture of the glass, for the purpose of obtaining a fiber end, which is flat, smooth, and perpendicular to the fiber axis.
18. Coating: The material surrounding the cladding of a fiber. Generally a soft plastic material that protects the fiber from damage.
19. Coaxial Cable: 1) A cable consisting of a center conductor surrounded by an insulating material and a concentric outer conductor and optional protective covering. 2) A cable consisting of multiple tubes under a single protective sheath. This type of cable is typically used for CATV, wideband, video, or RF applications.
20. Core: The light-conducting central portion of an optical fiber composed of material with a higher index of refraction than the cladding. The portion of the fiber that transmits light.
21. Coupler: An optical device that combines or splits power from optical fibers.
22. Coupling Ratio/Loss (CR, CL): The ratio/loss of optical power from one output port to the total output power, expressed as a percent. For a 1 x 2 WDM or coupler with output powers O1 and O2, and Oi representing both output powers.
23. CWDM: see Coarse-Wavelength-division-Multiplexing.
24. dBm: Abbreviation for decibel relative to milliwatt.
25. Decibel (dB): A unit of measurementindicating relative power on a logarithmic scale. Often expressed in reference to a fixed value, such as dBm or dBμ .
26. Dense Wavelength-division Multiplexing (DWDM): The transmission of many of closely spaced wavelengths in the 1550 nm region over a single optical fiber. Wavelength spacings are usually 100 GHz or 200 GHz which corresponds to 0.8 nm or 1.6 nm. DWDM bands include the C-Band, the SBand, and the L-Band.
27. Directional Coupler: A coupling device for separately sampling (through a known coupling loss) either the forward (incident) or the backward (reflected) wave in a transmission line.
28. Duplex Cable: A two-fiber cable suitable for duplex transmission.
29. DWDM: See dense wavelength-division multiplexing.
30. ESCON: Abbreviation for enterprise systems connection. A duplex optical connector used for computer-to-computer data exchange.
31. FDDI: Abbreviation for fiber distributed data interface.
1) A dual counter-rotating ring local area network.
2) A connector used in a dual counter-rotating ring local area network (illustrated).
32. Ferrule: A rigid tube that confines or holds a fiber as part of a connector assembly.
33. Fiber Optic Attenuator: A component installed in a fiber optic transmission system that reduces the power in the optical signal. It is often used to limit the optical power received by the photodetector to within the limits of the optical receiver. A fiber optic attenuator may be an external device, separate from the receiver, or incorporated into the receiver design.
34. Fiber Optic Cable: A cable containing one or more optical fibers.
35. Fiber Optic Communication System: The transfer of modulated or unmodulated optical energy through optical fiber media which terminates in the same or different media.
36. Fiber Optic Subsystem: A functional entity with defined bounds and interfaces which is part of a system. It contains solid state and/or other components and is specified as a subsystem for the purpose of trade and commerce.
37. Fiber-to-the-Curb (FTTC): Fiber optic service to a node connected by wires to several nearby homes, typically on a block.
38. Fiber-to-the-Home (FTTH): Fiber optic service to a node located inside an individual home.
39. Fiber Channel: An industry-standard specification that originated in Great Britain which details computer channel communications over fiber optics at transmission speeds from 132 Mb/s to 1062.5 Mb/s at distances of up to 10 kilometers.
40. Filter: A device which transmits only part of the incident energy and may thereby change the spectral distribution of energy.
41. Full-duplex Transmission: Simultaneous bidirectional transfer of data.
42. Fused Coupler: A method of making a multimode or single-mode coupler by
wrapping fibers together, heating them, and pulling them to form a central unified mass so that light on any input fiber is coupled to all output fibers.
43. Fused Fiber: A bundle of fibers fused together so they maintain a fixed alignment with respect to each other in a rigid rod.
44. Fusion Splicer: An instrument that permanently bonds two fibers together by heating and fusing them.
45. GRIN: Abbreviation for gradient index. Generally refers to the SELFOC lens often used in fiber optics.
46. Insertion Loss: The loss of power that results from inserting a component, such as a connector, coupler (illustrated), or splice, into a previously continuous path.
47. Interferometer: An instrument that uses to determine the endface geometry of optical endface parameters, These are available for both single fiber and multifiber connector ferrules.
48. Jacket: The outer, protective covering of the cable. Also called the cable sheath.
49. Jumper: A short fiber optic cable with connectors on both ends.
50. Kevlar®: A very strong, very light, synthetic compound developed by DuPont which is used to strengthen optical cables.
51. LAN (Local Area Network): A communication link between two or more points within a small geographic area, such as between buildings. Smaller than a metropolitan area network (MAN) or a wide area network (WAN).
52. Large Core Fiber: Usually, a fiber with a core of 200 μm or more.
53. Laser: Acronym for light amplification by stimulated emission of radiation. A light source that produces, through stimulated emission, coherent, near monochromatic light.
54. Launch Fiber: An optical fiber used to couple and condition light from an optical source into an optical fiber. Often the launch fiber is used to create an equilibrium mode distribution in multimode fiber. Also called launching fiber.
55. L-Band: The wavelength range between 1570 nm and 1610 nm used in some CWDM and DWDM applications.
56. Loose-tube: A type of fiber optic cable construction where the fiber is contained within a loose tube in the cable jacket.
57. MAN (Metropolitan Area Network): A network covering an area larger than a local area network. A series of local area networks, usually two or more, that cover a metropolitan area.
58. Mass Splicing: splicing of many fibers in a cable.
59. Material Dispersion: Dispersion resulting from the different velocities of each wavelength in a material.
60. Mechanical Splice: An optical fiber splice accomplished by fixtures or materials, rather than by thermal fusion. The capillary splice, illustrated, is one example of a mechanical splice.
61. Mode: A single electromagnetic wave traveling in a fiber.
62. Mode Coupling: The transfer of energy between modes. In a fiber, mode coupling occurs until equilibrium mode distribution (EMD) is reached.
63. Mode Field Diameter (MFD): A measure of distribution of optical power intensity across the end face of a single-mode fiber.
64. Multimode (MM) Fiber: An optical fiber that has a core large enough to propagate more than one mode of light The typical diameter is 62.5 micrometers.
65. Multiplexer: A device that combines two or more signals into one output.
66. Node:
1) A terminal of any branch in network topology or an interconnection common to two or more branches in a network.
2) One of the switches forming the network backbone in a switch network.
3) A point in a standing or stationary wave at which the amplitude is a minimum.
67. ONT: Abbreviation for optical network termination. Optical network element that terminates a line signal in installations where the fiber extends into the customer premises.
68. ONU: Abbreviation for optical network unit. A network element that is part of a fiber-in-the-loop system.
69. Optical Amplifier: A device that amplifies an input optical signal without converting it into electrical form. The best developed are optical fibers doped with the rare earth element, erbium. See also EDFA.
70. Optical Channel: An optical wavelength band for WDM optical communications.
71. Optical Channel Spacing: The wavelength separation between adjacent WDM channels.
72. Optical Fiber: A glass or plastic fiber that has the ability to guide light along its axis. The three parts of an optical fiber are the core, the cladding, and the coating or buffer.
73. Optical Isolator: A component used to block out reflected and unwanted light. Also called an isolator.
74. Optical Power Meter: An instrument that measures the amount of optical power present at the end of a fiber or cable.
75. Optical Return Loss (ORL): The ratio (expressed in dB) of optical power reflected by a component or an assembly to the optical power incident on a component port when that component or assembly is introduced into a link or system.
76. OTDR (Optical Time Domain Reflectometer): An instrument that locates faults in optical fibers or infers attenuation by backscattered light measurements.
77. Passive Branching Device: A device which divides an optical input into two or more optical outputs.
78. Passive Device: Any device that does not require a source of energy for its operation. Examples include electrical resistors or capacitors, diodes, optical fiber (photo), cable, wires, glass, lenses, and filters.
79. Pigtail: A short optical fiber permanently attached to a source, detector, or other fiber optic device at one end and an optical connector at the other.
80. Plastic Fiber: An optical fiber having a plastic core and plastic cladding.
81. PLC: Abbreviation for planar lightwave circuit. A device which incorporates a planar waveguide.
82. Plenum Cable: A cable whose flammability and smoke characteristics allow it to be routed in a plenum area without being enclosed in a conduit.
83. Polarization: The direction of the electric field in the lightwave. If the electric field of the lightwave is in the Y Axis, the light is said to be vertically polarized. If the electric field of the lightwave is in the X axis, the light is said to be horizontally polarized.
84. PON: Abbreviation for passive optical network. A broadband fiber optic access network that uses a means of sharing fiber to the home without running individual fiber optic lines from an exchange point, Telco CO, or a CATV headend and the subscriber’s home.
85. Radius of curvature: is the curvature of the ferrule endface measured immediately around the fiber core.
86. Return Loss: See optical return loss.
87. Ribbon Cables: Cables in which many fibers and / or copper wires are embedded in a plastic material in parallel, forming a flat ribbon-like structure.
88. Sheath: An outer protective layer of a fiber optic cable. Also called the cable jacket.
89. Simplex Cable: A term sometimes used for a single-fiber cable.
90. Single-mode (SM) Fiber: A small-core optical fiber through which only one mode will propagate. The typical diameter is 8-9 microns.
91. Splice: A permanent connection of two optical fibers through fusion or mechanical means.
92. Tee Coupler: A three-port optical coupler.
93. Transceiver: A device that performs, within one chassis, both telecommunication transmitting and receiving functions.
94. VCSEL: See vertical cavity surface-emitting laser.
95. Wavelength: The distance between points of corresponding phase of two consecutive cycles of a wave. The wavelength relates to the propagation velocity, and the frequency.
96. Wavelength-division Multiplexing (WDM): Sending several signals through one fiber with different wavelengths of light.
97. Wavelength Isolation: A WDM’s isolation of a light signal in the desired optical channel from the unwanted optical channels. Also called far-end crosstalk.
98. Wide Area Network (WAN): A physical or logical network that provides capabilities for a number of independent devices to communicate with each other over a common transmission-interconnected topology in geographic areas larger than those served by local area networks or metropolitan area networks.
99. Y Coupler: A variation on the tee coupler in which input light is split between two channels (typically planar waveguide) that branch out like a Y from the input.
100. Zipcord: A two-fiber cable consisting of two single fiber cables having conjoined jackets. A zipcord cable can be easily divided by slitting and pulling the conjoined jackets apart.

End Face: Term often used to describe the end of a ferrule. The end face is finished or polished to have a smooth end, which can minimize connector loss or backreflection. Typical polish types are PC, UPC, and APC.
UPC (Ultra Physical Contact): Specific to singlemode applications, referring to the endface geometry of a connector ferrule as well as performance characteristics (-55dB Return Loss).
PC (Physical Contact): Abbreviation for physical contact. Refers to an optical connector that allows the fiber ends to physically touch. Used to minimize backreflection and insertion loss.
APC (Angled Physical Contact): Abbreviation for angled physical contact. A style of fiber optic connector with a 5 -15 angle on the connector tip for the minimum possible backreflection.
OM1: Stands for 62.5/125um multi-mode fiber and used for Ethernet systems using LEDs as transmitters. Multi-mode fibers are described using a classification system put in place by the ISO 11801 standard.
OM2: Stands for 50/125um multi-mode fiber and used for Ethernet systems using LEDs as transmitters. Multi-mode fibers are described using a classification system put in place by the ISO 11801 standard.
OM3: Stands for laser-optimized 50/125um multi-mode fiber and used for systems with high bandwidth such as 10 Gigabit Ethernet using Lasers as transmitters. Multi-mode fibers are described using a classification system put in place by the ISO 11801 standard.
OM4: OM4 fiber is a laser-optimized, high bandwidth 50um multimode fiber. OM4 fiber is not a new fiber type. All major fiber manufacturers have been selling a fiber with an effective modal bandwidth (EMB) value equivalent to that specified by OM4 since 2005. The change is that there is now a standard that is specifically targeted at this product. Prior to the standardization of OM4, these higher bandwidth fibers were sold as a part of OM3.
OFNP: Optical Fiber Nonconductive Plenum, Cable installed in ducts, plenums, and other spaces used for environmental air must be listed as having adequate fire-resistant and low-smoke producing characteristics.
OFNR: Optical Fiber Nonconductive Riser, Optical fiber cable used in vertical shafts, or in runs between floors, must have fire-resistant characteristics capable of preventing the spread of fire from floor-to-floor. OFNR refers to the fiber rating of the cable jacketing.
LSZH: Primarily used for indoor applications, Low Smoke Zero Halogen (LSZH) cable is designed to reduce toxic emissions in event of fire.
Aramid Yarn: Yellow fibers that provide cable tensile strength, support, and additional protection for the optical fiber bundle. Kevlar? is a particular brand of aramid yarn.
Kevlar: A very strong, very light, synthetic compound developed by DuPont which is used to strengthen optical cables.
Coating: The material surrounding the cladding of a fiber. Generally a soft plastic material that protects the fiber from damage.
Cladding: Material that surrounds the core of an optical fiber. Its lower index of refraction, compared to that of the core, causes the transmitted light to travel down the core.


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