| Term |
Definition |
A
|
|
| Absorption |
Loss
of power in an optical fiber, resulting from conversion of optical
power into heat and caused principally by impurities, such as transition
metals and hydroxylions, and also by exposure to nuclear radiation. |
| APC |
Angle polished
connector. A 5º to 15º angle on the connector tip for minimum
possible back reflection. |
| APD |
Avalanche
photodiode. A photodiode that exhibits internal amplification of photocurrent
through avalanche multiplication of carriers in the junction region.
|
| Apodization
|
Overall shape
and sharpness of filter. |
| AR Coating
|
Antireflection
coating. A thin dielectric or metallic film applied to an optical
surface to reduce its reflections and thereby increase its transmittance |
| AWG |
Array Waveguide
Gratings |
| |
|
| B |
|
| Bandwidth |
A range of frequencies. Translates into signal carrying capacity of
the fiber or communication system. |
| BER |
Bit
Error Rate. The ratio of incorrectly transmitted bits to correctly
transmitted bits. |
| Bi-Directional
Module |
An
active fiber optic component that can simultaneously launch and receive
light over a single fiber. |
| Buffer |
A
protective layer over the fiber, such as a coating, an inner jacket
or a hard tube. |
| Buffer
coating |
A
protective layer, such as an acrylic polymer, applied over the fiver
cladding for protective purposes. |
| |
|
| C |
|
| Chromatic
Dispersion |
All fiber has
the property that the speed an optical pulse travels depends on its
wavelength. This is caused by several factors including material dispersion,
wave guide dispersion and profile dispersion. The net effect is that
if an optical pulse contains multiple wavelengths (colors), then the
different colors will travel at different speeds and arrive at different
times, smearing the received optical signal. |
| Cladding |
The
outer concentric layer that surrounds the fiber core and has lower
index of refraction than the core. |
| Collimator
|
A device that
renders divergent or convergent rays nearly parallel. |
| Connector |
A
device for making connectable/disconnectable connections of a fiber
to another fiber, source, detector, or other devices. |
| Core |
The
central, light carrying part of the optical fiber; it has an index
of refraction higher than that of the surrounding cladding |
| Coupler |
An
optical device that combines or splits power from optical fibers. |
| Critical
Angle |
In geometric
optics, at a refractive boundary, the smallest angle of incidence
at which total internal reflection occurs. |
| Cutoff
Wavelength |
For
single-mode fiber, the wavelength above which the fiber exhibits single-mode
operation. |
| |
|
| D |
|
| Dark
Current |
The
thermally induced current that exists in a photodiode in the absence
of incident optical power. |
| dB |
Decibel |
| dBm |
Decibel
referenced to a milliwatt |
| dBm |
Decibel
referenced to a microwatt |
| Demultiplexing
|
The separation
of two or more channels previously multiplexed (combined). |
| Detector |
An
optoelectronic transducer used in fiber optics for converting optical
power to electric current. In fiber optics, usually a photodiode. |
| Dichroic
Filter |
An optical filter
that transmits light according to wavelength. Dichroic filters reflect
light that they do not transmit. |
| Diffraction
Grating |
An
array of fine, parallel, equally spaced reflecting or transmitting
lines that mutually enhance the
effects of diffraction to concentrate the diffracted light in a few
directions determined by the spacing of the lines and by the wavelength
of the light.
|
| Dispersion |
The
temporal spreading of a light signal in an optical wave guide caused
by light signals traveling at different speeds through a fiber either
due to modal or chromatic effects. |
| |
|
| E |
|
| ELED |
Edge
emitting, Light emitting diode. A light emitting diode with a special
output that emanates from between the heterogeneous layers, i.e. from
the edge. |
| EMI |
Electromagnetic
interference. |
| Erbium-Doped
Fiber Amplifier |
Optical fibers
doped with the rare earth element erbium, which can amplify light
in the 1550 nm region when pumped by an external fight source. |
| Excess
Loss |
In
a fiber optic coupler, the optical loss from that portion of light
that does not emerge from the nominally operational ports of the device. |
| Extrinsic
loss |
In
a fiber interconnection, that portion of loss that is not intrinsic
to the fiber but is related to the imperfect joining, which may be
caused by the connector or splice. |
|
|
| F |
|
| FBG |
Fiber Bragg
Grating |
| Ferrule |
A
rigid tube that confines or holds a fiber as part of a connector assembly. |
| Fiber
Grating |
An optical fiber
in which the refractive index of the core varies periodically along
its length, scattering light in a way similar to a diffraction grating,
and transmitting or reflecting certain wavelengths selectively. |
| Fiber
Optic Attenuator |
A component installed
in a fiber optic transmission system that reduces the power in the
optical signal. It is often used to limit the optical power received
by the photo detector to within the limits of the optical receiver. |
| Fiber
Optic Cable |
A cable containing
one or more optical fibers. |
| Fiber-to-the-Curb
(FTTC) |
Fiber optic service
to a node connected by wires to several nearby homes, typically on
a block. |
| Fiber-to-the-Home
(FTTH) |
Fiber optic service
to a node located inside an individual home. |
| Fused
Coupler |
A method of making
a multimode or single-mode coupler by wrapping fibers together, heating
them, and pulling them to form a central unified mass so that light
on any input fiber is coupled to all output fibers. |
| FWHM |
Acronym
for Full Width at Half Maximum. |
| FWHP |
Acronym
for Full Width, Half Power |
| |
|
| G |
|
| Graded-Index
Fiber |
Optical
fiber in which the refractive index of the core is in the form of
a parabolic curve, decreasing toward the cladding. |
| GRIN
|
Gradient index.
Generally refers to the SELFOC lens often used in fiber optics. |
|
|
| H |
|
| Heatsink |
High
thermal conductivity mount that dissipates the heat generated during
cw or near cw operation of the diode laser, LEDs or microwave devices.
Typical heatsink materials are copper and diamond. |
| |
|
| I |
|
| IDP |
Integrated
detector/preamplifier. A detector package containing a pin photodiode
and transimpedance amplifier. |
| Index
of Refraction |
Also refractive
index. The ratio of the velocity of light in free space to the velocity
of light in a fiber material. Symbolized by n. Always greater than
or equal to one. |
| Infrared
(IR) |
The region of
the electromagnetic spectrum bounded by the long-wavelength extreme
of the visible spectrum (about 0.7 pm) and the shortest microwaves
about 0.1 mm). See also frequency, light. |
| InGaAs |
Indium
Gallium Arsenide |
| InGaAsP |
Indium Gallium Arsenide Phosphide |
| Inter-channel
Isolation |
The ability
to prevent undesired optical energy from appearing in one signal path
as a result of coupling from another signal path. Also called cross
talk. |
| Intrinsic
Losses |
Splice losses
arising from differences in the fibers being spliced. |
| Isolator |
A
device intended to prevent return reflections along a transmission
path.
|
|
|
| K |
|
| Kink |
Strong
non-linearity in the light output vs. current input of a diode laser.
|
| |
|
| L |
|
| Laser |
A light source producing, through stimulated emission, coherent, near
monochromatic light. |
| LED |
Light
emitting diode. A semiconductor diode that spontaneously emits light
from the pm junction when forward current is applied. |
| L-I
Curve |
Characteristic
of diode laser or LED displaying the output light power vs. the
input drive current. |
| Local
area network |
a geographically limited network interconnecting electronic equipment. |
| |
|
| M |
|
| Material
Dispersion |
Dispersion resulting
from the different velocities of each wavelength in a material. |
| Mechanical
Splice |
An optical fiber
splice accomplished by fixtures or materials, rather than by thermal
fusion. |
| Multimode
Fiber |
An optical fiber that has a core large enough to propagate more than
one mode of light The typical diameter is 62.5 micrometers. |
| Multiplexing |
The process by which two or more signals are transmitted over a single
communications channel. Examples include time-division multiplexing
and wavelength-division multiplexing. |
| |
|
| N |
|
| NA |
Numerical
aperture |
| Near-End
Cross Talk |
The optical power
reflected from one or more input ports, back to another input port.
Also known as isolation directivity.
|
| Numerical
Aperture (NA) |
The light-gathering
ability of a fiber; the maximum angle to the fiber axis at which light
will be accepted and propagated through the fiber. The measure of
light acceptance angle of an optical fiber. NA = sin x, where x is
the acceptance angle. NA is also used to describe the angular spread
of light from a central axis, as in exiting a fiber, emitting from
a source, or entering a detector |
| |
|
| O |
|
| Optical
Attenuator |
In
an optical fiber data link or integrated optical circuit, a device
used to reduce the intensity |
| Optical
Channel Spacing |
The wavelength
separation between adjacent WDM channels. |
| Optical
Channel Width |
The optical wavelength
range of a channel. |
| Optical
Directional Coupler (ODC) |
A component used
to combine and separate optical power. |
| Optical
Isolator |
A component used
to block out reflected and unwanted light. Used in laser modules,
for example. Also called an isolator. |
| Optical
Return Loss |
The ratio (expressed
in units of dB) of optical power reflected by a component or an assembly
to
the optical power incident on a component port when that component
or assembly is introduced into a link or system.
|
| Optical
Rise Time |
The time interval
for the rising edge of an optical pulse to transition from 10% to
90% of the pulse amplitude. Alternatively, values of 20% and 80% may
be used. |
| |
|
| P |
|
| Photodector |
An
optoelectronic transducer, such as a pin photodiode or avalanche photodiode.
|
| Photodiode |
A
semiconductor diode that produces current in response to incident
optical power and used as a detector in fiber optics |
| Photon |
A
quantum of electromagnetic energy. A "particle" of light. |
| Pigtail |
A
short length of fiber permanently attached to a component, such as
a source, detector or coupler. |
| Pin
Photodiode |
a
photodiode having a large intrinsic layer sandwiched between p-type
and n-type layers. |
| Planar
Waveguide |
A waveguide fabricated
in a flat material such as thin film. |
| Plastic-Clad
Silica Fiber |
An
optical fiber having a glass core and plastic coating. |
| PMD |
Polarization
mode dispersion is an inherent property of all optical media. It is
caused by the
difference in the propagation velocities of light in the orthogonal
principal polarization states of the transmission medium. The net
effect is that if an optical pulse contains both polarization components,
then the different polarization components will travel at different
speeds and
arrive at different times, smearing the received optical signal.
|
| Polarization
|
The direction
of the electric field in the lightwave |
| |
|
| R |
|
| Refractive
Index |
A property of
optical materials that relates to the speed of light in the material. |
| Responsivity |
The
ratio of a photodetector's electrical output to its optical input
in amperes/watt. |
| |
|
| S |
|
| Single-Mode
Fiber |
A
small-core optical fiber through which only one mode will propagate.
The typical diameter is 8-9 microns. |
| Splice |
An
interconnection method for joining the ends of two optical fibers
in a permanent or semi permanent fashion. |
| Step
Index Fiber |
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. |
| Spectral
Width |
A
measure of the wavelength extent of a spectrum. |
| |
|
| T |
|
| TDM |
Time
Division Multiplexing. A transmission technique whereby several low
speed channels are multiplexed into a high speed channel for transmission.
Each low speed channel is allocated a specific position based on time.
|
| TFF |
Thin Film Filter |
| Threshold
Current |
The
driving current corresponding to the lasing threshold. |
| |
|
| W |
|
| Wavelength |
The
distance between the same two points on adjacent waves; the time required
for a wave to complete a single cycle. |
| WDM |
Wavelength Division Multiplexing Sending several signals
through one fiber with different wavelengths of light. |
| |
|
