Attenuation
Loss of signal power between points. In optical cables, attenuation
is a ratio of input power vs. output power, measured in decibels per
unit length, usually dB/km.
Attenuation
Coefficient
A factor expressing optical power loss per unit of length, expressed
in dB/Km.
Backbone
A high-speed transmission system used to connect relatively distant
points. Backbone networks can be used to join autonomous networks
within buildings or between different buildings.
Bandwidth
The information carrying capacity of a fiber. The bandwidth for a
given wavelength is the lowest frequency at which optical power has
decreased by 3 dB and is expressed in MHz•km.
Bend Radius
The radius of curvature that an optical fiber cable can bend without
causing harmful effects on the optical or mechanical performance of
the cable.
Chromatic
Dispersion
Different wavelengths travel along an optical medium at different
speeds. Wavelengths reach the end of the medium at different times,
causing the light pulse to spread. This chromatic dispersion is expressed
in picoseconds (of dispersion) per kilometer (of length) per nanometer
(of source bandwidth). It is the sum of material and waveguide dispersion.
Cladding
The layer of material, usually glass, that immediately surrounds the
fiber core. The cladding is usually coated with another material to
provide protection when handling.
Cleave
The process of cutting 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. Coating A material applied
to the cladding for protective purposes.
Concentricity
In a wire or cable, the measurement of the location of the center
of the conductor with respect to the geometric center of the circular
insulation.
Core
The central part of the glass construction through which light is
transmitted.
Core Eccentricity
A measure of the displacement of the center of the core relative to
the cladding center. Critical angle The smallest angle at which a
meridional ray may be totally reflected within a fiber at the core-cladding
interface.
Cut-off Wavelength
The wavelength at which a singlemode fiber transmits a single mode
of light.
Decibel (dB)
The standard unit used to express gain or loss of optical power. A
standard logarithmic unit for the ratio of two powers, voltages or
currents. In fiber optics, the ratio is power.
Dielectric
Nonmetallic. All-dielectric designs are inherently nonconductive;
all-dielectric cables contain no metal and are lightning resistant.
Dispersion
The cause of bandwidth limitations in a fiber. Dispersion causes a
broadening of input pulses along the length of the fiber. Two major
types are: mode dispersion caused by differential optical path lengths
in a multimode fiber and material dispersion caused by a differential
delay of various wavelengths of light in a waveguide material.
EIA
Electronic Industry Association.
Ethernet Standards
Not all Ethernet and IEEE 802.3 standards are identical. In fact,
in some instances, there are enough differences in Ethernet standards
to cause major problems. In a network environment (such as Ethernet
Version 1.0 and IEEE 802.3) nodes can coexist and communicate properly
on a network but the important link is overall transceiver-to-node
integrity.
Fiber Distributed
Date Interface (FDDI)
An ANSI standard to ensure compatibility of components from different
manufacturers.
Fiber Optics
Light transmission through optical fibers for communication or signaling.
Frequency
The number of cycles per unit of time, denoted by Hertz (Hz). 1 Hertz
= 1 cycle per second.
Graded Index
A core refractive index profile that varies with the radius of the
core.
Halogens
Chemicals from the halogen family (chlorine, fluorine, bromine) are
typically compounded into plastic materials to improve the flame retardance.
When the materials are exposed to a high heat source, halogen gases
are released, limiting the spread of flames but potentially causing
a health hazard.
Hertz
The unit of frequency, in cycles per second.
Hypalon
A thermoset jacket material providing excellent abrasion and flex
fatigue resistance; flame and oil resistance; and resistance to weather,
ozone, and oxidizing chemicals. Ideal for industrial and petrochemical
applications.
Insertion
Loss
Total optical power loss caused by insertion of an optical component
such as a connector, splice, or coupler into a previously continuous
path.
ISDN (Integrated
Services Digital Network)
ISDN is an international standard for transmitting digital information
(text, sound, voice, data, video, etc.)
Jumper
Fiber optic cable that has connectors terminated on both ends.
Kevlar
The trademark of the Dupont Company for aramid yarn used as strength
members.
KPSI
Tensile strength in thousands of pounds per square inch.
LAN
Local Area Network.
Laser
A device that produces monochromatic, coherent light through stimulated
emission. Most lasers used in fiber optic communications are solid-state
semiconductor devices.
Light Emitting
Diode (LED)
A semiconductor device which emits incoherent light from a p-n junction.
Loose Tube
Buffering
A cable construction in which the optical fiber is placed in a plastic
tube having an inner diameter much larger than the fiber itself. The
loose tube isolates the fiber from the exterior mechanical forces
acting on the cushion. The space between the tube and the fiber is
often filled with a gel to cushion the fiber.
Loss Budget
The total acceptable loss for a given system from transmitter to receiver.
Includes cables, splices and connectors.
Low Smoke,
Zero Halogen (LSZH)
Thermoplastic or thermoset jacketing compounds that emit limited smoke
and no halogens when exposed to high sources of heat.
Material Dispersion
Pulse dispersion due to the variations in a material's refractive
index as a function of wavelength.
Macrobending
In an optical fiber, all macroscopic deviations of the fiber's axis
from a straight line; distinguished from microbending.
Microbending
Minute but severe bends in fiber that result in light displacement
and increased loss. Most microbending can be avoided by the correct
selection of materials and proper cabling, handling, and installation
techniques.
Mode
A path of light through a fiber.
Mode Field
Diameter (MFD)
In singlemode fiber, the region in which the light transmitted is
larger than the glass core diameter. This mode field diameter is a
measured value and often listed as a requirement with core diameter
in fiber specifications.
Neoprene
A rubber elastomer jacket material providing excellent cold temperature
flexibility, abrasion resistance and flame retardance. Ideally suited
for outdoor, field deployable cables and repeated flexing applications.
Pigtail
A fiber optic cable that has a connector on only one end.
Plenum Cable
A cable whose flammability and smoke characteristics allow it to be
routed in a plenum area without being enclosed in a conduit.
Polyethylene
(PE)
Tough, chemical and moisture resistant jacketing material, ideal for
outdoor cables.
Polyurethane
A jacketing material used mostly for outdoor cables. Provides excellent
abrasion resistance and low temperature flexibility.
PolyVinylChloride
(PVC)
Flame retardant jacketing material providing good mechanical protection,
flexibility, and abrasion resistance. Ideally suited for indoor cables.
Refraction
The bending of a beam of light at an interface between two dissimilar
media or in a medium whose refractive index is a continuous function
of position (graded-index medium).
Refractive
Index
The ratio of the speed of light in a vacuum to the speed of light
in a material. Also called Index of Refraction.
Riser Cable
Indoor cables made especially for between floor applications.
Singlemode
Fiber
An optical fiber that supports only one mode of light propagation
above the cutoff wavelength.
Step Index
A refractive index profile characterized by a uniform refractive index
within the core and a sharp decrease at the core-cladding interface.
Strength Member
That part of a fiber optic cable composed of aramid yarn, steel strands,
or fiberglass filaments that increase the tensile strength of the
cable.
Thermoplastic
A plastic jacketing material that softens when heated and becomes
firm on cooling. Thermoplastics include PVC, PE, Polyurethane, and
Nylon.
Thermoset
A jacketing material where the molecules have been cross-linked (interlocked)
through exposure to heat or irradiation. Once the material is "set,"
it cannot be softened or melted by re-heating. Thermosets include
Neoprene and Hypalon.
Tight Buffer
In tight buffer constructions the thermoplastic is extruded directly
over the coated fiber, increasing the outside diameter to 900 micron
(0.9 mm), an industry standard.
Waveguide
Dispersion
Dispersion caused by the fact that light travels at different speeds
in the core and cladding of singlemode fibers.
Zero Dispersion
Wavelength In singlemode fibers, the wavelength at which the effects
of chromatic dispersion and waveguide dispersion are lowest; thus
providing the greatest information carrying capacity.
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