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Aramid Yarn – Fibers, yellow, that provide cable tensile strength, support, and additional protection of the optical fiber bundles. Kevlar® is a particular brand of aramid yarn.
Armor – Protective material in cable made of corrugated steel which offers protection from rodents and some crush resistance.
Attenuation - A measure of the decrease in energy transmission (loss of light) expressed in dB/Km. In optical wave guides attenuation is primarily due to absorption losses and scattering losses.
Backbone Cable – The portion of a telecommunications network that provides connections between closets, equipment rooms, and entrance facilities.
Bandwidth - The capacity of an optical fiber to transmit information expressed in bits of information transmitted in a specific time period for a specific length of optical wave guide. (Usually expressed in megabits/sec./km.) Bandwidth is limited by pulse spreading or broadening due to dispersion, so that adjacent pulses overlap and cannot be distinguished.
Bend Radius – Maximum bend allowed before physical damage is incurred. Generally expressed for two conditions, loaded (under tensile load) or unloaded.
Broadband – Denotes transmission facilities capable of handling a wide range of frequencies simultaneously, thus permitting multiple channels in data systems.
Buffer – Material used to protect an optical fiber or cable from physical damage and providing mechanical isolation or protection. Fabrication techniques include both tight jacket or loose tube buffering, as well as multiple buffer layers.
Buffer Tubes – A protective tubing used to protect exposed fiber. Commonly used in terminating multi-fiber cable or “fan-out” situations. Also referred to as furcation tubing.
Central Member – The center component of a cable used to provide strength. Commonly referred to as “Central Strength Member.”
Cladding - A low refractive index, glass or plastic that surrounds the core of a fiber. Optical cladding promotes total internal reflection for the propagation of light in a fiber.
Composite Cable – A cable containing both fiber and copper conductors.
Core - The light conducting portion of a fiber, defined by its high refraction index. The core is the center of a fiber, surrounded by concentric cladding of lower refractive index.
Duplex Cable (fiber optics) - A cable that contains two optical fibers in a single cable structure. Light is not coupled between the two fibers; typically one is used to transmit signals in one direction and the other used to transmit in the opposite direction.
Ethernet – A network protocol standard for a 10 Mbit/s local area network. Also, “Fast Ethernet” (100 Mbit/s) and “Gigabit Ethernet” (1000 Mbit/s)
Fan-Out – A multi-fiber cable constructed in a tight buffered tube design. At a termination point, cable fibers must be separated from the cable to their separate connection positions.
Ferrule - A component of fiber optic connectors that holds a fiber in place and aids in its alignment. It is the protruding portion of the connector, made of Ceramic, Stainless Steel, or Polymer, and is polished during the connection process to form a smooth finish.
FDDI – A standard for a 100 Mbit/s optical fiber local area network.
Fiber Buffer - Material used to protect an optical fiber or cable from physical damage, providing mechanical isolation or protection. Fabrication techniques include both tight jacket or loose tube buffering, as well as multiple buffer layers.
FTTH – “Fiber to the Home" FTTH is where fiber will be brought directly to the side of your home to support your cable TV, telephone service and Internet needs. It looks much like the utility box that you currently have on the side of your home, only with fiber jumpers inside.
Furcation Tubing – A protective tubing used to protect exposed fiber. Commonly used in terminating multi-fiber cable or “fan-out” situations. Also referred to as buffer tubing.
Fusion Splicer - A high precision piece of equipment that allows the user to 'melt' or fuse the ends of two optical fibers together to create one continous fiber. There is typically very low loss at this junction. Alignment of fibers can be by manual or automatic manipulation. The fusing takes place by electrical discharge between two electrodes.
Graded Index Fiber - An optical fiber in which the refractive index changes gradually between the core and cladding, in a way designed to refract light so it stays in the fiber core. Such fibers have lower dispersion and hence broader bandwidth than step-index fibers.
High Index (HI) Fiber – Designed with a higher core index and a more precise core/clad geometry to reduce the fiber’s bend attenuation. HI fibers are used within optical networking components, and play an integral role inside many high performance optical communications devices including optical amplifiers, transmission lasers, and dispersion compensation modules.
Hybrid Cable – A fiber optic cable containing two or more different types of fiber, such as 62.5um multimode and singlemode.
Kevlar - DuPont brand of aramid yarn used to provide strain relief in cable assemblies.
Kilometer (km) – One thousand meters, or approximately 3,281 feet. The kilometer is a standard unit of length measurement in fiber optics. Conversion is 1 ft. = 0.3048 mtrs.
kpsi - A unit of force per area expressed in thousands of pounds per square inch. Usually used as the specification for fiber proof test, e.g., 500 kpsi.
Laser - An acronym for Light Amplification by the Stimluated Emission of Radiation, applied to a wide range of devices which produce light by that principle. Compared with other light sources, laser light covers a narrow range of wavelengths. Tends to be coherent, and is emitted in a directional beam.
LED (Light-Emitting Diode) - A semiconductor device in which light is produced when current carriers combine at a p-n junction. The emission is spontaneous and there are no feedback mirrors, unlike diode lasers. Output is lower in power than from diode lasers, reflecting the use lower operating currents. Generally LEDs are less expensive than diode lasers, and can operate at shorter wavelengths without the rapid degradation that occurs with visible-wavelength diodes.
Link Length – Referring to the distance over which an optic fiber will carry a coherent signal relative to the rate of transmission.
Loose Buffer Cable - Loose buffered designs consist of a loose tube surrounding a coated fiber. It also includes an aramid braid as the strength member for improved flexibility.
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) - A unit of length equal to one-millionth (10 E-6) of a meter (same as a micrometer).
Mode Conditioning Patchcord - A duplex multimode cord that has a small length of singlemode fiber at the start of the transmission leg. The basic principle behind the cord is that you launch your laser into the small section of singlemode fiber. The other end of the singlemode fiber is coupled to the multimode section of the cable with the core offset from the center of the multimode fiber. The laser light thus misses the "dip" and this new launch condition more closely mimics a standard LED launch. The bonus is that you still retain the speed advantages of using a laser.
Multimode - An optical waveguide with a much larger core (50um +) than the singlemode waveguide core (2 to 9um) and which permits approximately 1000 modes to propagate through the core compared to only one mode through a singlemode fiber.
Nonzero Dispersion-Shifted Fiber – A fiber whose properties are dispersion shifted to a region other than the point of zero dispersion. Corning’s LEAF fiber is an example of this fiber.
Numerical Aperture (NA) - The numerical aperture of an optical fiber defines a characteristic of the fiber in terms of its acceptance of light. The "degree of openess," "light gathering ability" and "acceptance cone" are all terms describing this characteristic.
Optical Return Loss (ORL) - A reflection that travels down the fiber back to the source. In high speed systems this is undesirable because it can interfere with the transmission. Also referred to as “back reflection”.
Optical Time Domain Refectometer (OTDR) – A method for characterizing a fiber via an optical pulse transmitted through the fiber. The resulting backscatter and reflections are measured as a function of time. The OTDR is useful in measuring attenuation over distance, identification of defects and other losses.
Patchcord - A length of cable with connectors at both ends. Also known as jumpers.
Pigtail – A short length of optical fiber with a connector on one end and no connector on the other end.
Plastic Fibers – Optical fibers in which both core and cladding are made of plastic material. Typically their transmission is much poorer than that of glass fibers, and their lowest losses are in the visible region.
Plenum – An air-handling space such as that found above drop-ceiling tiles or in raised floors. Also, a fire code rating for indoor cable.
Polarization-Maintaining Fiber – A singlemode optical fiber that maintains the polarization of the light that entered it, normally by including some birefringence within the fiber itself. Normal singlemode fibers, and all other types, allow polarization to be scrambled in light transmitted through them.
Polyethylene (PE) – A type of plastic material used for outside plant cable jackets.
Polyvinyl-chloride (PVC) – A type of plastic material used for cable jacketing. Typically used in flame-retardant cables.
Pulse Suppressor – A launching fiber used to take up the unmeasurable beginning (dead zone) of an OTDR.
PVDF (Kynar®) – Abbreviation used to denote polyvinyldifluoride. A type of material used for cable jacketing. Often used in plenum-rated cables.
Reflection – The abrupt change in direction of a light beam at an interface between two dissimilar media so that the light beam returns into the media from which it originated.
Return Loss – Expressed in negative value (–dB), this refers to the amount of back reflection. The lower the dB value, the better the connector and polish finish on the connector ferrule.
Riser – Pathways for indoor cables that pass between floors. It is normally a vertical shaft or space. Also a fire-code rating for indoor cable.
Simplex Cable – A single cable structure with a single fiber.
Singlemode – One type of low-loss optical waveguide with a very small Core (2-9 microns). It reguires a laser source for input signals because of the very small entrance aperture. The smallness of the core radius approaches the wavelength of the source. Consequently, only a singlemode is propagated.
Step-Index – An optical fiber, either multimode or single mode, in which the core refractive index is uniform throughout so that a sharp step in refractive index occurs at the core-to-cladding interface. It usually refers to a multimode fiber. Such fibers have a large numerical aperture, and are simple to connect, but have lower bandwidth than other types of optical fibers.
Tight Buffered Cable – A protective coating extruded tightly over fiber for mechanical and environmental protection. The coating material is either nylon or PVC. This buffering offers excellent physical and flexing properties, but higher micro-bending sensitivity.
Zero-Dispersion Wavelength – Wavelength at which the chromatic dispersion of an optical fiber is zero. Occurs when waveguide dispersion cancels out material dispersion.
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