Glossary
Yellow fibers that provide cable tensile strength, support, and additional protection of the optical fiber bundles. Kevlar® is a particular brand of aramid yarn.
It’s a continuously welded
longitudinally applied steel tape used inside outdoor optical
cables. It provides high crush resistance and prevents water
penetration which makes it a suitable choice for outside
plant application.
It’s a spirally wrapped aluminum or steel
armor used for indoor/ outdoor cable application. It provides
flexibility and high crush resistance which makes it suitable
for areas requiring extra protection for optical cables.
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.
The portion of a telecommunications
network that provides connections between closets,
equipment rooms, and entrance facilities.
Maximum bend allowed before physical
damage is incurred. Generally expressed for two conditions,
loaded (under tensile load) or unloaded.
Denotes transmission facilities capable of
handling a wide range of frequencies simultaneously, thus
permitting multiple channels in data systems.
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.
A protective tubing used to protect fiber.
Commonly used as a subunit in multi-fiber cable.
The center component of a cable used
to provide strength. Commonly referred to as “Central
Strength Member.”
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.
A cable containing both fiber and
copper conductors.
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.
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.
A network protocol standard for a 10 Mbit/s
local area network. Also, “Fast Ethernet” (100 Mbit/s) and
“Gigabit Ethernet” (1000 Mbit/s)
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.
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.
A standard for a 100 Mbit/s optical fiber local area
network.
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.
This term is used to denote the point at which optical
fiber is extended to the end user. The variable “x” can
represent a curb, business, home, node or other termination
point, after which fiber may transition to copper cable.
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.
“melt” or fuse the ends of two optical fibers
together to create one continuous 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.
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.
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.
A fiber optic cable containing two or more
different types of fiber, such as 62.5mm multimode and
singlemode.
DuPont brand of aramid yarn used to provide strain
relief in cable assemblies.
An acronym for Light Amplification by the Stimulated
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.
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 of 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.
Referring to the distance over which an
optic fiber will carry a coherent signal relative to the rate of
transmission.
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.
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.
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.
An optical waveguide with a much larger core
(50mm +) than the singlemode waveguide core (2 to 9mm)
and which permits approximately 1000 modes to propagate
through the core compared to only one mode through a
singlemode 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.
The numerical aperture of an
optical fiber defines a characteristic of the fiber in terms
of its acceptance of light. The “degree of openness,” “light
gathering ability” and “acceptance cone” are all terms
describing this characteristic.
Cable
that has been subjected to and passed the UL 1666 flame
propagation test in accordance with Article 770 of the
National Electrical Code.
Cable
that has been subjected to and passed the NFPA 262 flame
propagation and smoke-density test in accordance with
Article 770 of the National Electrical Code.
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”.
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.
A length of cable with connectors at both ends.
Also known as jumpers.
A short length of optical fiber with a connector on
one end and no connector on the other end.
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.
A type of thermo plastic material used
for outside plant cable jackets.
A type of thermo plastic material
used for cable jacketing. Typically used in flame-retardant
cables.
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.
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.
Pathways for indoor cables that pass between floors.
It is normally a vertical shaft or space.
A single cable structure with a single fiber.
One type of low-loss optical waveguide
with a very small Core (2-9 microns). It requires 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.
An optical fiber, either multimode or singlemode,
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.
A protective coating extruded tightly
over fiber for mechanical and environmental protection. The
coating material is typically nylon or PVC. This buffering
offers excellent physical and flexing properties, but higher
micro-bending sensitivity.
Wavelength at which the
chromatic dispersion of an optical fiber is zero. Occurs when
waveguide dispersion cancels out material dispersion.