Fiber Optics Glossary
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Acceptance
Angle
The halfangle of the cone
within which incident light is totally internally reflected by
the fiber core. It is equal to Arcsin (NA).
Amplitude Modulation
A transmission technique in
which the amplitude of the carrier is varied in accordance with
the signal.
Amplitude Modulation (AM)
A means of signal transmission
whereby transmitter (light source) signal intensity is varied
in relation to the amplitude of the input signal.
Analog
A format that uses continuous
physical variables such as voltage amplitude or frequency variations
to transmit information.
Angle of Incidence
The angle between an incident
ray and the normal to a reflecting surface.
Aramid Yarn
Strength element used in Siecor
cable to provide support and additional protection of the fiber
bundles. Kevlar is a particular brand of aramid yarn.
Armoring
Additional protection between
jacket layers that provides protection against severe outdoor
environments. Usually made of plasticcoated steel, and may
be corrugated for flexibility.
Attenuation
(1) Limited Operation The condition
in a fiber optic link when operation is limited by the power of
the received signal (rather than by bandwidth or by distortion).
(2) The decrease in magnitude of power of a signal in transmission
between points. A term used for expressing the total losses on
an optical fiber consisting of the ratio of light output to light
input. Attenuation is usually measured in decibels per kilometer
(db/km) at a specific wavelength. The lower the number, the better
the fiber. Typical multimode wavelengths are 850 and 1300
nanometers (nm); singlemode, at 1300 and 1500 nm. NOTE: When specifying
attenuation, it is important to note if it is nominal or average,
room temperature, value or maximum over operating range.
Attenuator
A passive optical component
that intentionally reduces the optical power propagating in a
fiber.
APD (Avalanche Photodiode)
A photodiode designed to take
advantage of avalanche multiplication of photocurrent. As the
reversebias voltage approaches the breakdown voltage,
holeelectron pairs created by absorbed photons acquire sufficient
energy to create additional holeelectron pairs when they
collide with ions; thus a multiplication or signal gain is achieved.
Average Power
The average level of power
in a signal that varies with time.
Axial Ray
A light ray that travels along
the axis of an optical fiber.
B.P.S.
(Bits Per Second)
The number of energy pulses
passing a given point in a transmission medium in one second.
Backscattering
A small fraction of light that
is deflected out of the original direction of propagation by scattering
suffers a reversal of direction. In other words, it propagates
in the optical waveguide towards the transmitter.
Back Reflection
Connector Pysical Contact (PC)
connectors provide a back reflection characteristic exceeding
<-30 dB. Super Pysical Contact (SPC) connectors provide a back
reflection characteristic exceeding <-40 dB. Ultra Pysical
Contact (UPC) connectors provide a back reflection characteristic
exceeding <-50 dB. Angled Pysical Contact (APC) connectors
provide a back reflection characteristic exceeding <-60 dB.
Also see Reflectance.
Bandpass
A range of wavelengths over
which a component will meet specifications.
Bandwidth Limited Operation
The condition prevailing when
the system bandwidth, rather than the amplitude of the signal,
limits performance. The condition is reached when modal dispersion
distorts the shape of the waveform beyond specified limits.
Bandwidth
Information carrying capacity
of an optical fiber. Expressed in MHzkm, specifies the analog
bandwidth capability or number of digital transitions per second
the fiber can sustain over a 1 km distance. Bandwidth is dependent
upon wavelength and type of light source.
Baseband
A method of communication in
which a signal is transmitted at its original frequency without
being impressed on a carrier.
BAUD
A unit of signaling speed equal
to the number of signal intervals per second, which may or may
not be equal to the data rate in bits per second. In some encoding
schemes, such as Non Return to Zero (NRZ). equals data rate. In
others, such as Manchester encoding, two transitions per bit are
required.
Beamsplitter
A device used to divide an
optical beam into two or more separate beams.
Bend Radius
Radius a fiber can bend before
the risk of breakage or increase in attenuation. Also can refer
to cable bend radius.
Bend Loss
A form of increased attenuation
in a fiber that results from bending a fiber around a restrictive
curvature (a macrobend) or from minute distortions.
Bend Radius
The lower limit below which
fiber or cable should not be bent for reasons of optical and mechanical
performance.
BER
Bit error rate. Specifies expected
frequency of errors. The ratio of incorrectly transmitted bits
to correctly transmitted bits.
Bit
A binary digit, the smallest
element of information in binary system. A 1 or 0 of binary data.
BreakOut Cable
See FanOut Cable.
Broadband
The ability of a system to
carry a multitude of signals simultaneously. In data transmission,
it denotes transmission facilities capable of handling frequencies
greater than those required for highgrade voice communications.
The higher frequency allows the carrying of several simultaneous
channels. Broadband infers the use of a carrier signal rather
than direct modulation (i.e., baseband).
BUFFER
The protective coating over
a fiber. The primary buffer (i.e., next to the cladding) is 250
microns in diameter. A secondary buffer of 900 micron diameter
is used on indoor cables.
Buffered Fiber
Fiber protected with an additional
material (hytrel or nylon) to provide ease in handling, connectorization
and increased tensile strength.
Buffering
(1) A protective material extruded
directly on the fiber coating to protect it from the environment
(2) Extruding a tube around the coated fiber to allow isolation
of the fiber from stresses on the cable.
Building Entrance
Terminal Cable entrance point
where typically a trunk cable between buildings is terminated
and fiber is then distributed through the building.
Bundle
Many individual fibers contained
within a single jacket or buffer tube. Also, a group of buffered
fibers distinguished in some fashion from another group in the
same cable core.
Bus Network
A network topology in which
all terminals are attached to a transmission medium serving as
a bus.
BUS
Commonly called '"data
bus"", term used to describe the physical linkage between
stations on a network sharing some common communication.
Byte
A unit of 8 bits (Digital Data).
Cable Assembly
Fiber optic cable that has
connectors installed on one or both ends. General use of these
cable assemblies includes the interconnection of multimode
and singlemode fiber optical cable systems and optoelectronic
equipment. If connectors are attached to only one end of the cable,
it is known as a pigtail. If connectors are attached to both ends,
it is known as a jumper.
Cable Bend Radius
Cable bend radius during installation
infers that the cable is experiencing a tensile load. Free bend
infers a lower allowable bend radius since it is at a condition
of no load.
Carrier Sense Multiple Access With Collision Detection
(CSMA/CD)
A technique used to control
the transmission channel of a local area network to ensure that
there is no conflict between terminals that wish to transmit.
CCMQJ
Certified Commercial measurement
Quality Jumper. A high quality reference cable designed to provide
accurate and consistent test results.
Center Wavelength(s)
The nominal operating wavelength(s).
Central Member
The center component of a cable. It serves as an antibuckling
element to resist temperatureinduced stresses. Sometimes
serves as a strength element. The central member is composed of
steel, fiberglass, or glassreinforced plastic. Central Office
(CO)
The place where communications common carriers terminate customer
lines and locate switching equipment that interconnects those
lines.
Channel
A communications path or the
signal sent over that channel. Through multiplexing several channels,
voice channels can be transmitted over an optical channel.
Chromatic Dispersion
Spreading of a light pulse
caused by the difference in refractive indices at different wavelengths.
Cladding
The material surrounding the
core of an optical fiber. The cladding must have a lower index
of refraction in order to steer the light in the core.
Cladding Mode
A mode confined to the cladding;
a light ray that propagates in the cladding.
Coating
A material put on a fiber during
the drawing process to protect it from the environment.
Conduit
Pipe or tubing through which
cables can be pulled or housed.
Connector
A mechanical device used to
align and join two fibers together to provide a means for attaching
and decoupling it to a transmitter, receiver or another fiber.
Commonly used connectors include the FC, FCPC, Biconic, ST ConnectorCompatible,
D4, SMA 905 or 906.
Core
The central region of an optical
fiber through which light is transmitted.
Core Eccentricity
A measure of the displacement
of the center of the core relative to the cladding center.
Coupler
(1) A passive device that distributes
optical power among two or more ports. (Can be in various ratios.)
Commonly called a splitlet. (2) A multipod device used to distribute
optical power.
Coupler
An optical device that coupes
(or splits) light in accordance with its number of input and output
legs.
Coupling Efficiency
The efficiency of optical power
transfer between two components.
Coupling Ratio
The percentage of light transferred
to a receiving output port with respect to the total power of
all output ports.
Coupling Loss
The power loss suffered when
coupling light from one optical device to another.
CPC
Customer Premises Communication.
CPE
Customer Premises Equipment.
Critical Angle
The smallest angle from the
fiber axis at which a ray may be totally reflected at the core/cladding
interface.
Cutoff Wavelength
The shortest wavelength at
which only the fundamental mode of an optical waveguide is capable
of propagation.
Data
Rate
The maximum number of bits
of information which can be transmitted per second, as in a data
transmission link. Typically expressed as megabits per second
(mb/s). dbm Decibel referenced to a milliwatt. dbp Decibei referenced
to a microwatt.
dBm
Output power of a signal referenced
to an input signal of 1mW (Milliwatt). 0 dBm = 1 mW.
Decibel (dB)
Unit for measuring the relative
strength of a signal. Power level referenced in decibels to a
microwatt.
Demultiplex
The process of separating optical
channels.
Detector
(1) A transducer that provides
an electrical output signal in response to an incident optical
signal. The current is dependent on the amount of light received
and the type of device. (2)A semiconductor device which converts
optical energy to electrical energy.
DiameterMismatch Loss
The loss of power at a joint
that occurs when the transmitting half has a diameter greater
than the diameter of the receiving half. The loss occurs when
coupling light from a source to fiber, from fiber to fiber, or
from fiber to detector.
Dielectric
Nonmetallic and, therefore,
nonconductive. Glass fibers are considered dielectric. A
dielectric cable contains no metallic components.
Digital
A data format that uses two
physical levels to transmit information. A discrete or discontinuous
signal.
Direetivity
Also referred to as nearend
crosstalk, it is the amount of power observed at a given input
port with respect to an initial input power.
Dispersion
The cause of bandwidth limitations
in a fiber. Dispersion causes a broadening of input pulses along
the length of the fiber. Three major types are: (a) mode dispersion
caused by differential optical path lengths in a multimode fiber;
(b) material dispersion caused by a differential delay of various
wavelengths of light in a waveguide material; and (c) waveguide
dispersion caused by light traveling in both the core and cladding
materials in singlemode fibers.
DistortionLimited Operation
Generally synonymous with bandwidthlimited
operation.
Duplex Cable
A twofiber cable suitable
for duplex transmission.
Duplex Transmission
Transmission in both directions,
either one direction at a time (half duplex) or both directions
simultaneously (full duplex).
Duty Cycle
In a digital transmission,
the ratio of high levels to low levels.
DWDM (Dense Wavelength Division Multiplexing)
The transmission of many 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 wavelength range between
1530 nm and 1562 nm), the S-Band (the wavelength region between
1485 nm and 1520 nm), and the L-Band (The wavelength range between
1570 nm and 1610 nm).
EIA
Electronic Industries Association.
A standards association that publishes test procedures. See FOTP.
EIA/TIA
Electronics Industry Alliance/Telecommunications
Industry Association A standards association that publishes test
procedures and specifications for the telecommunications industry.
Electromagnetic Interference (EMI)
Any electrical or electromagnetic
interference that causes undesirable response, degradation, or
failure in electronic equipment. Optical fibers neither emit nor
receive EMI.
EMD
Equilibrium Mode Distribution.
Encoding
A scheme to represent digital
ones and zeros through combining high and low signal voltage states.
Excess Loss
(1) In a fiberoptic coupler,
the optical loss from that portion of light that does not emerge
from the nominally operational pods of the device.
(2)The ratio of the total output power of a passive component
with respect to the input power.
FanOut
Cable
Multifiber cable constructed
in the tight buffered design. Designed for ease of connectorization
and rugged applications for intra or interbuilding requirements.
Ferrule
A small alignment tube attached
to the end of the fiber and used in connectors. Generally made
of stainless steel, alumina, or zirconia, used to confine and
align the stripped end of a fiber.
Fiber Distributed Data Interface (FDDI)
A standard for a 100 Mbit/s
fiber optic local area network.
Fiber Optic Link
Any optical fiber transmission
channel designed to connect two end terminals or to be connected
in series with other channels.
Fiber
Thin filament of glass. An
optical waveguide consisting of a core and a cladding which is
capable of carrying information in the form of light.
Fiber Optics
Light transmission through
optical fibers for communication or signalling.
FOTP
Fiber Optic Test Procedures.
FOTS
Fiber Optic Transmission System.
Frequency
The number of pulses or cycles
per second; measured in units of Hertz (Hz) where 1 hertz equals
1 pulse/cycle per second.
Frequency Modulation (FM)
Transmission scheme whereby
information is sent by varying the frequency of an optical carrier.
A method of transmission in which the carrier frequency varies
in accordance with the signal.
Fresnel Reflection
The reflection of a portion
of the light incident on a planar surface between two homogeneous
media having different refractive indices. Fresnel reflection
occurs at the air/glass interfaces at entrance and exit ends of
an optical fiber.
Fundamental Mode
The lowest order mode of a
waveguide.
Fusion Splicing
A permanent joint accomplished
by the application of localized heat sufficient to fuse or melt
the ends of the optical fiber, forming a continuous single fiber.
Fusion Splice
A joining of two fibers by
physically fusing through heat the two fiber ends.
Gap
Loss
Loss resulting from the end
separation of two axially aligned fibers.
Grade Index
Fiber design in which the refractive
index of the core is lower toward the outside of the fiber core
and increases toward the center of the core; thus it bends the
rays inward and allows them to travel faster in the lower index
of refraction region. This type of fiber provides high bandwidth
capabilities.
Ground Loop Noise
Noise that results when equipment
is grounded at ground points having different potentials and thereby
created an unintended current path. The dielectric of optical
fibers provide electrical isolation that eliminates ground loops.
Hard
Clad Silica
A fiber with a hard plastic
cladding surrounding a silica glass core.
Hybrid Cable
A fiber optic cable containing
two or more different types of fiber, such as 62.5 µm multimode
and single-mode.
Icky Pick
A substance frequently found in loose tube outdoor cables. In a
loose-tube setup, one or more fibers (usually up to 12) are installed
inside of a plastic tube that resembles a drinking straw, and the
assembly is then bound into the cable. Frequently, these tubes are
filled with a water-block gel (usually and descriptively called
"icky-pick" on the job site), which prevents water from
entering the cable.
IEEE
Institute of Electrical and
Electronics Engineering.
Index Matching Material
A material, often a liquid
or cement whose refractive index is nearly equal to the core index,
used to reduce Fresnel reflections from a fiber end face.
Index of Refraction
The ratio of light velocity
in a vacuum to its velocity in a given transmitting medium.
Index Profile
Curve of the refractive index
over the cross section of an optical waveguide.
INDEX OF REFRACTION
An optical characteristic
(n) of a material, referencing the speed of light in that material
to a vacuum.
Insertion Loss
The attenuation caused by
the insertion of an optical component; in other words, a connector
or coupler in an optical transmission system.
Isolation
Also referred to as farend
crosstalk or farend isolation. Predominantly used in
reference to WDM products, it is a measure of light at an undesired
wavelength at any given port.
Jumper
Fiber optic cable that has
connectors installed on both ends. See also cable assembly.
Kevlar
See Aramid Yarn.
Kilometer
One thousand meters or 3,281
feet. The kilometer is a unit of measurement for fiber optics.
KPSI
A unit of tensile strength
expressed in thousands of pounds per square inch.
Laser
Light
Amplification by Stimulated
Emission of Radiation. A device which produces coherent light
with a narrow range of wavelengths.
Lateral Displacement Loss
The loss of power that results
from lateral displacement from optimum alignment between two fibers
or between a fiber and an active device.
Launch Angle
Angle between the propagation
direction of the incident light and the optical axis of an opticat
waveguide.
Launching Fiber
A fiber used in conjunction
with a source to excite the modes of another fiber in a particular
way. Launching fibers are most often used in test systems to improved
the precision of measurements.
Light
In the laser and optical communication
fields, the portion of the electromagnetic spectrum that can be
handled by the basic optical techniques used for the visible spectrum
extending from the near ultraviolet region of approximately 0.3
micron, through the visible region and into the midinfrared
region of about 30 microns.
LED (Light Emitting Diode)
A semiconductor diode which
emits light when forward biased to an optical signal. A device
used in a transmitter to convert information from electric to
optical form. It typically has a large spectral width.
Lightguide Cable
An optical fiber, multiple
fiber, or fiber bundle which includes a cable jacket and strength.
Lightwaves
Electromagnetic waves in the
region of optical frequencies. The term "light" was
originally restricted to radiation visible to the human eye, with
wavelengths between 400 and 700 nanometers (nm). However, it has
become customary to refer to radiation in the spectral regions
adjacent to visible light (in the near infrared from 700 to about
2000 nm) as "light" to emphasize the physical and technical
characteristics they have in common with visible light.
Link
A fiber optic cable with connectors
attached to a transmitter (source) and receiver (detector).
LLDPE
Linear Low Density Polyethylene
jacketing.
Local Area Network (LAN)
A geographically limited communications
network intended for the local transport of data, video and voice.
Loose Tube
A protective tube loosely
surrounding a cabled fiber, often filled with a water blocking
gel.
LOOSE TUBE
Type of cable design, primarily
for outdoor use, where one or more fibers are enclosed in hard
plastic tubes. Fibers are usually buffered to 250 microns.
Loss
Attenuation of optical signal,
normally measured in decibels.
Macrobending
Macroscopic axial deviations
of a fiber from a straight line, in contrast to microbending.
Material Dispersion
See Dispersion.
MDPE
Medium Density Polyetheylene
jacketing.
Mechanical Splicing
Joining two fibers together
by mechanical means to enable a continuous signal. Elastomeric
splicing is one example of mechanical splicing.
Megahedz (MHz)
A unit of frequency that is
equal to one million hertz.
Microbending
Curvatures of the fiber which
involve axial displacements of a few micrometers and spatial wavelengths
of a few millimeters. Microbends cause loss of light and consequently
increase the attenuation of the fiber.
Micron (um)
Another term for micrometer.
One millionth of a meter. 10exp6 meter.
Misalignment Loss
The loss of power resulting
from angular misalignment, lateral displacement, and end separation.
Modal Dispersion
Pulse spreading due to multiple
light rays traveling different distances and speeds through an
optical fiber.
Mode Field Diameter (MFD)
The diameter of optical energy
in a singlemode fiber. Because the MFD is greater than the core
diameter, MFD replaces core diameter as a practical parameter.
Mode Filter
A device used to remove highorder
modes from a fiber and thereby simulate EMD.
Mode Scrambler
A device composed of one or
more optical fibers in which strong mode coupling occurs. Frequently
used to provide a mode distribution that is independent of source
characteristics.
Mode
A term used to describe a
light path through a fiber, as in multimode or singlemode.
Mode Mixing
The numerous modes of a multimode
fiber differ in their propagation velocities. As long as they
propagate independently of each other, the fiber bandwidth varies
inversely with the fiber length due to multimode distortion.
As a result of inhomogenejties of the fjber geometry and of the
index profile, a gradual energy exchange occurs between modes
with differing velocities. Due to this mode mixing, the bandwidth
of long multimode fibers is greater than the value obtained by
linear extrapolation from measurements on shod fibers.
MODE
A light path through a fiber.
Modulation
Coding of information onto
the carrier frequency. This includes amplitude, frequency, or
phase modulation techniques.
Monochromatic
Consisting of a single wavelength.
In practice, radiation is never perfectly monochromatic but, at
best, displays a narrow band of wavelengths.
MQJ
Measurement Quality Jumper.
A high quality reference cable designed to provide accurate and
consistent test results. Note: The U.S. Navy requires that MQJ's
are used to test all Navy shipboard fiber installations.
MultiMode Fiber
An optical waveguide in which
light travels in multiple modes. Typical core/cladding sizes (measured
in microns) are 50/125, 62.5/125, and 100/140.
Multimode Fiber
A fiber type which supports
multiple light paths through its core.
Multiplex
The combination of several
signals onto a single communications channel.
Multiplexing
The process by which two or
more signals are transmitted over a single communications channel.
Examples include timedivision multipiexing and wavelengthdivision
multiplexing.
NAMismatch
Loss
The loss of power at a joint
that occurs when the transmitting half has an NA greater than
the NA of the receiving half. The loss occurs when coupling light
from a soume to fiber, from fiber to fiber, or from fiber to detector.
Nanometer
A unit of measurement equal to one billionth of a meter. 10exp9
meter.
NEC
National Electrical Code.
Defines building flammatory requirements for indoor cables.
Numerical Aperture
A numerical value that expresses
the light gathering ability of a fiber. The imaginary cone which
defines the acceptance area for the fiber core to accept rays
of light.
OFC
Optical Fiber Conductive.
OFCP
Optical Fiber Conductive Plenum.
OFCR
Optical Fiber Conductive Riser.
OFN
Optical Fiber Non-conductive.
OFNP
Optical Fiber Non-conductive
Plenum.
OFNR
Optical Fiber Non-conductive
Riser.
Optical Time Domain Reflectometer (OTDR)
A method for characterizing
a fiber wherein an optical pulse is transmitted through the fiber
and the resulting backscatter and reflections to the input are
measured as a function of time. Useful in estimating attenuation
coefficient as a function of distance and identifying defects
and other localized losses.
Optical Fiber
See Fiber.
Optical Waveguide
Dielectric waveguide with
a core consisting of optically transparent material of low attenuation
(usually silica glass) and with cladding consisting of optically
transparent material of lower refractive index than that of the
core. It is used for the transmission of signals with lightwaves
and is frequently referred to as fiber. In addition, there are
planar dielectric waveguide structures in some optical components,
such as laser diodes, which are also referred to as optical waveguides.
Optoelectronic
Pertaining to a device that
responds to optical power, emits or modifies optical radiation,
or utilizes optical radiation for its internal operation. Any
device that functions as an electricaltooptical or opticaltoelectrical
transducer.
OTDR
Optical time domain Reflectometer.
A test instrument, working on the principal of continuous energy
backscatter, which provides a complete characterization of fiber
loss along its length.
Patch
Panel
A centralized location for
cross-connecting, monitoring and testing telecommunications cabling.
PCM
PulseCoded Modulation.
PCS
PlasticClad Silica.
PE
Abbreviation used to denote
polyethylene. A type of plastic material used to make cable jacketing.
Peak Wavelength
The wavelength at which the
optical power of a source is at a maximum.
Photocurrent
The current that flows through
a photosensitive device, such as a photodiode, as the result of
exposure to radiant power.
Photodetector
An optoelectronic transducer,
such as a pin photodiode or avalanche photodiode.
Photodiode
A diode designed to produce
photocurrent by absorbing light. Photodiodes are used for the
detection of optical power and for the conversion of optical power
into electrical power.
Photon
A quantum of electromagnetic
energy.
Physical Contact (PC)
Connectors aligned and mated
so that no air gaps exist between them. Positive contact between
fibers exist. Also see Connector Back Reflection.
Pigtail
Fiber optic cable that has
connectors installed on one end. See also Cable Assembly.
PIN Photodiode
A diode with a large intrinsic
region sandwiched between pdoped and ndoped semiconducting
regions. Photons in this region create electron hole pairs that
are separated by an electric field thus generating an electric
current in the load circuit.
Plastic Fiber
An optical fiber having a
plastic core and plastic cladding.
PlasticClad Silica Fiber
An optical fiber having a
glass core and plastic cladding.
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.
Plenum Cable
A cable whose flammability
and smoke characteristics allow it to be routed in a plenum area
without being enclosed in a conduit. PointtoPoint A
connection established between two specific locations, as between
two buildings.
Polarization Stability
The variation in insertion
loss as the polarization state of the input light is varied.
Preform
A glass structure from which
an optical fiber waveguide may be drawn.
Prefusing
Fusing with a low current
to clean the fiber end. Precedes fusion splicing.
Primary Coating
The plastic coating applied
directly to the cladding surface of the fiber during manufacture
to preserve the integrity of the surface.
Pulse Spreading
The dispersion of an optical
signal with time as it propagates through an optical fiber.
PUR
Polyurethane. Material used
in manufacture of a type of jacketing material.
PVC
Polyvinyl Chloride. Material
used in manufacture of a type of jacketing material.
Receiver
An electronic package which
converts optical signals to electrical signals.
Receiver Sensitivity
The optical power required
by a receiver for low error signal transmission. In the case of
digital signal transmission, the mean optical power is usually
quoted in Watts or dbm (decibels referred to 1 milliwatt).
Reflectance
Light that is reflected back
along the path of transmission, from either the coupling region,
the connector or a tertninated fiber.
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.
Refraction
The bending of a beam of light
at an interface between two dissimilar media or a medium whose
refractive index is a continuous function of position (graded
index medium).
Refractive Index
See Index of Refraction.
Regenerative Repeater
A repeater designed for digital
transmission that both amplifies and reshapes the signal.
Repeater
A device which consists of
a transmitter and a receiver or transceiver, used to regenerate
a signal to increase the system length.
Return Loss
See reflectance.
Ring Network
A network topology in which
terminals are connected in a pointtopoint serial fashion
in an unbroken circular configuration.
Rise Time
The time it takes the signal
output to rise from low levels to peak value. Usually measured
from 10% to 90% of max. output.
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.
Scattering
A property of glass which
causes light to deflect from the fiber and contributes to losses.
Sensitivity
For a fiberoptic receiver,
the minimum optical power required to achieve a specified level
of performance, such as a BER.
SignaltoNoise Ratio (SNR)
The ratio of signal power
to noise power. Measured in dB.
Simplex Cable
A term sometimes used for
a singlefiber cable.
Simplex Transmission
Transmission in one direction
only.
SingleMode Fiber
An optical waveguide (or fiber)
in which the signal travels through its core. The fiber has a
smaller core diameter.
SMA
A connector type with screw
threads.
Source
The means used to convert
an electrical information carrying signal to a corresponding optical
signal for transmission by fiber. The source is usually a Light
Emitting Diode (LED) or Laser.
Spectral Width
A measure of the extent of
a spectrum. For a source, the width of wavelengths contained in
the output at one half of the wavelength of peak power. Typical
spectral widths are 20 to 60 nm for an LED and 2 to 5 nm for a
laser diode. The width of wavelengths in a light pulse, based
on 50% intensity.
Splice Closure
A container used to organize
and protect splice trays.
Splice Tray
A container used to organize
and protect spliced fibers.
Splice
(1)A permanent joint between
two optical waveguides. (2)Means for joining two fiber ends.
Splicing
The permanent joining of fiber
ends to identical or similar fibers, without the use of a connector.
See also Fusion Splicing and Mechanical Splicing.
Splitting Loss
See coupling ratio.
ST
A connector type with a bayonet
housing which is spring loaded "ST" stands for "straight
tip".
Star Coupler
An active or passive device
where energy presented at an input port is distributed through
several output ports.
Star Network
A network in which all terminals
are connected through a single point, such as a star coupler.
StepIndex
Fiber Optical fiber which
has an abrupt ("step") change in its refractive index,
due to a core and cladding that have different indices or refraction.
Typically used for single mode.
Strength Member
That part of a fiber optic
cable composed of Kevlar aramid yarn, steel strands, or fiberglass
filaments that increase the tensile strength of the cable.
Tap
Loss
In a fiber optic coupler,
the ratio of power at the tap port to the power at the input port.
Tap Port
In a coupler in which the
splitting ratio between output pods is not equal, the output port
containing the lesser power.
Tee Coupler
A ThreePod Optical Coupler.
Thermal Stability
A measure of insertion loss
variation as the device undergoes various environmental changes.
Tight Buffer
Type of cable construction
whereby each glass fiber is tightly buffered by a protective thermoplastic
coating to a diameter of 900 microns. High tensile strength rating
achieved, providing durability, ease of handling and ease of connectorization.
TimeDivision Multiplexing (TDM)
A transmission technique whereby
several lowspeed channels are multiplexed into a highspeed
channel for transmission.
Topology
The physical layout of a network.
Total Internal Reflection
Total reflection of light
back into a material when it strikes the interface of a material
having a lower index at an angle below the critical angle.
Transceiver
An electronic device which
has both transmit and receive capabilities.
Transducer
A device for converting energy
from one form to another, such as optical energy to electrical
energy.
Transmission Loss
Total loss encountered in
transmission through a system.
Transmitter
An electronic package which
converts an electrical signal to an optical signal.
Tree Coupler
A passive fiber optical component
in which power from one input is distributed to more than two
output fibers.
UL
Underwriters Laboratories,
Inc.
Uniformity
The maximum insertion loss
difference between ports of a coupler.
Waveguide
Structure that guides electromagnetic
waves along its length. An optical fiber is an optical waveguide.
Wavelength Division Multiplexing (WDM)
Simultaneous transmission
of several signals in an optical waveguide at differing wavelengths.
Wavelength
The distance between two crests
of an electromagnetic waveform.
Wavelength Dependence
The variation in an optical
parameter caused by a change in the operating wavelength.
WAVELENGTH DIVISION MULTIPLEXING (WDM)
The process of using multiple
wavelengths to carry multiple signals on a single fiber.
WAVELENGTH
The distance between two peaks
on an electromagnetic waveform.
WDM
Wavelength Division Multiplexer
a passive fiber optical device used to separate signals of different
wavelengths carried on one fiber.
WIC
Wavelength Independent Coupler.