Components

245
GLOSSARY
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Glossary
Fiber Glossary of Terms
Coating: A protective material applied directly over
the cladding of the fiber during the draw process to
protect the fiber from the environment and handling.
Composite Cable: A cable containing both fiber
and copper media per Article 770 of the National
Electrical Code (NEC).
Conduit: A pipe or tube that may be buried
or installed within buildings through which cables
can be pulled or housed. Synonym for duct.
Core, Cable: The central portion of a cable containing
the optical fibers and surrounded by a sheath.
Core, Fiber: The central region of an optical fiber
through which light is transmitted. Fiber cores have a
higher index of refraction than the cladding
in order to contain the light.
Decibel (dB): The unit for measuring the relative
strength of light signals (attenuation), normally
expressed in dB.
Dielectric Cable: A cable that contains no electrically
conducting materials such as metal. Glass fibers are
considered dielectric. Dielectric cables are some-
times used in areas subject to high lightning or elec-
tromagnetic interference.
Distribution Cable: Generally tight buffered fiber
cables used for various indoor applications.
Distribution cables are usually 6 thru 144 fiber count
cables.
Duct: See conduit.
Duplex Cable: A cable containing 2 fibers. Standard
configurations are duplex round and duplex zip.
Electromagnetic Interference (EMI): Any electrical
interference that causes undesirable interference or
failure in electronic equipment. Optical fibers neither
emit nor receive EMI.
Fiber: An optical fiber is a thin piece of glass used for
transmitting optical signals. An optical fiber consists
of three layers: the core, cladding and coating. It is
capable of carrying information in the form of light.
Fiber Bend Radius: Radius a fiber can bend before
the risk of breakage or increase in attenuation.
Fiber Distributed Data Interface (FDDI):
A transmission standard for a fiber optic local area
network.
Fiber Optics: Light transmission through optical fibers
for communication or signaling.
Grounding: Connecting the metal components of a
cable sheath to earth, generally through a ground
rod.
Hybrid Cable: A fiber optic cable containing two
or more different types of fiber. The most common
hybrid includes 62.5/125 µm multimode mixed with
Single mode fiber.
Inside Plant: Tight buffered fiber optic cables used
for indoor applications.
Interbuilding: Refers to between buildings.
Interconnect: Tight buffer cables such as simplex,
duplex and quad cables.
Intrabuilding: Refers to within buildings.
Jacket: A plastic extrusion over a cable. Kevlar®: A
strong material used in cable strength members. The
name is a trademark of the Dupont Company.
Kilometer (km): One thousand meters, or approxi-
mately 3,281 feet, or 0.62 miles. The kilometer is
a standard unit of length measurement in fiber optics.
LAN (Local Area Network): See Local Area Network.
Lashing: Attachment of a cable to a support strand
by wrapping steel wire helically around them.
Local Area Network (LAN): A geographically limited
communications network intended for the local
transport of voice, data and video.
Loose Tube Cable: A type of cable construction
where the fibers are encased in buffer tubes hav-
ing a diameter several times larger than the fiber
offering excellent fiber protection and segregation.
This design offers excellent protection for outdoor
environments.
Macrobending: Visible bends often caused by
exceeding suggested bend radius of a cable.
Megahertz (MHz): A unit of frequency that is equal to
one million cycles per second.
Microbending: A small fiber bend, invisible to the
unaided eye, that results in light displacement and
increased loss. They can occur due to coating,
cabling, installation and temperature.
Minimum Bend Radius: The amount of bend a fiber
(or cable) can withstand before experiencing prob-
lems in performance.
Mode: A term used to describe an independent light
path through a fiber. Only one mode propagates in a
Single mode fiber whereas several modes propagate
in a multimode fiber.
Mode Field Diameter (MFD): The diameter of the
one mode of light propagating in a Single mode fiber.
Since the mode field diameter is larger than the core
diameter, it replaces core diameter as the practical
parameter in Single mode fiber. Synonym for spot
size.
Multifiber Cable: An optical fiber cable that contains
two or more fibers.
Multimode Fiber (MM): A type of optical fiber in
which light travels in multiple modes. The most com-
mon multimode fiber sizes (core/cladding) are 50/125
and 62.5/125.
National Electrical Code (NEC): Defines flammability
requirements for cables installed within buildings.
(Local codes take precedence but may refer to or
require compliance to the NEC.)
Nanometer (nm): A unit of measurement
typically used to express the wavelength of light.
Nonmetallic Cable: See dielectric cable.
Optical Fiber: See Fiber.
Plenum: A compartment or chamber to which one or
more air ducts are connected and that forms part of
the air distribution system (i.e. the space above the
drop ceiling).
Polarization Mode Dispersion (PMD): The
broadening of a light pulse due to the time delay
of one of the two pulse components. If significant
enough, the result is a bit error.
RoHS: (The Restriction of Hazardous Substances
Directive) RoHS 2002/95/EC was adopted in February
2003 by the European Union. The RoHS took effect on
July 1, 2006, but is not a law; it is simply a directive
for participating countries, including the European
Union (exclusive of the United States and many other
countries). This directive restricts the use of six
hazardous materials in the manufacture of various
types of electronic and electrical equipment.
RoHS is often referred to as the "lead-free" directive.
Scattering: A property of the fiber that causes light to
change direction, contributes to optical attenuation.
Sheath: The protective outer covering of a cable
core, including metallic shields and jackets.
Single mode Fiber (SM): An optical fiber in which the
signal travels in one mode. The fiber has a small core
diameter, typically 8.3 µm.
Spot Size: See mode field diameter.
Stranding: The manufacturing process by which
cable components, such as buffer tubes and yarns,
are helically assembled around a central member
forming a round core.
Strength Member: The part of a fiber optic cable
composed of aramid yarns or fiberglass that increase
the tensile strength of the cable.
Tensile Strength: The pulling strength or force nec-
essary to break a material.
Thermoplastic:
A material that softens with heat but
returns to its original condition when cooled.
Tight-Buffered Cable: Type of cable construction
where the plastic buffer is applied directly over the
coating on the fiber to a diameter of 900 µm.
Outside Plant: The portion of a cable network that
resides outside of buildings.
PE: Abbreviation used to denote polyethylene.
A type of thermoplastic material used for outside
plant cable jackets.
Riser cables: Riser cables are intended for use in
elevator (vertical) shafts between floors in a building.
They are OFNR listed (UL 1666). Also a fire-code rat-
ing for indoor cable connectorization.
Wavelength: The distance between two successive
points on adjacent waves, usually measured in nano-
meters (nm).
Window: A range of wavelengths within which a
fiber best operates.