Glossary
Term | Main definition |
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Modal noise |
A disturbance often measured in multimode fiber-optic
transmissions that are fed by diode lasers. The higher
quality the laser light feeding the fiber, the less modal
noise will be measured.
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Mode |
A single wave traveling in an optical fiber or in a light
path through a fiber. Light has modes in optical-fiber
cable. A high-order mode is a path that results in numerous
reflections off the core/cladding interface. A loworder
mode results in fewer reflections. A zero-order
mode is a path that goes through the fiber without
reflecting off the interface at all. In a single-mode fiber,
only one mode (the fundamental mode) can propagate
through the fiber. Multimode fiber has several hundred
modes that differ in field pattern and propagation velocity.
The number of modes in an optical fiber is determined
by the diameter of the core, the wavelength of the
light passing through it, and the refractive indexes of
the core and cladding. The number of modes increases
as the core diameter increases, the wavelength decreases,
or the difference between refractive indexes increases.
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Mode field diameter (MFD) |
The actual diameter of the light beam traveling through
the core and part of the cladding and across the endface
in a single-mode fiber-optic cable. Since the mode
field diameter is usually greater than the core diameter,
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Mode filter |
A device that can select, attenuate, or reject a specific
mode. Mode filters are used to remove high-order
modes from a fiber and thereby simulate EMD. See also
mandrel wrap.
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Mode stripper |
A device that removes high-order modes in a multimode
fiber to give standard measurement conditions.
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Modem |
A device that implements modulator-demodulator functions
to convert between digital data and analog signals.
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Modem Lead | A standard lead used for internet connections. Connecting PC/ Modem to BT outlet. Using 2 Pair telephone cable (CW1308) terminated with RJ11 Plug on both ends.
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Modified modular jack (MMJ) |
A six-wire modular jack used by the DEC wiring system.
The MMJ has a locking tab that is shifted to the righthand
side.
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Modular |
Equipment is said to be modular when it is made of plugin
units that can be added together to make the system
larger, improve the capabilities, or expand its size.
Faceplates made for use with structured cabling systems
are often modular and permit the use of multiple types
of telecommunications outlets or modular jacks such as
RJ-45, coaxial, audio, or fiber.
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Modular jack |
A female telecommunications interface connector.
Modular jacks are typically mounted in a fixed location
and may have four, six, or eight contact positions,
though most typical standards-based cabling systems
will have an eight-position jack. Not all positions need be
equipped with contacts. The modular jack may be keyed
or unkeyed so as to permit only certain types of plugs to
be inserted into the jack.
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Modulate |
(1) To convert data into a signal that can be transmitted
by a carrier. (2) To control.
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Modulation |
(1) Coding of information onto the carrier frequency.
Types of modulation include amplitude modulation
(AM), frequency modulation (FM), and phase
modulation (PM). (2) When light is emitted by a medium,
it is coherent, meaning that it is in a fixed-phase relationship
within fixed points of the light wave. The light is
used because it is a continuous, or sinusoidal, wave (a
white or blank form) upon which a signal can be superimposed
by modulation of that form. The modulation is
a variation imposed upon this white form, a variation
of amplitude, frequency, or phase of the light. There are
two basic forms of this modulation: one by an analog
form, another by a digital signal. This signal is created
in the form of the
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Monochromatic |
Light having only one color, or more accurately only one
wavelength.
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MORAN | Multiple-Operator Radio Access Network configuration
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Motion Pictures Experts Group (MPEG) |
A standards group operating under the ISO that develops
standards for digital video and audio compression.
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