Glossary
Tunable Laser Source
77
channel
A communication path. For WDM systems, a channel is
determined by a wavelength and width.
chromatic dispersion
A phenomenon caused by the wavelength dependence of
the group velocity in an optical fiber. Since any practical light
source has a certain spectral width, chromatic dispersion
results in pulse broadening. The coefficient describing
chromatic dispersion per unit length is generally given in
units of ps/nm·km
CNR
Carrier-to-noise ratio
coherence
A phenomenon whereby the phases of the photons (or
constituent wavetrains) of a light beam maintain a definite
relationship with each other. A narrow-linewidth laser is said
to exhibit a high “degree of coherence”.
connector
A junction that allows an optical fiber or cable to be
repeatedly connected or disconnected to a device such as a
source or detector.
core eccentricity
A measure of the displacement of the core center relative to
the cladding center.
core ellipticity
(non-circularity)
A measure of the departure of the core from roundness.
coupler
A device whose purpose is to distribute optical power
among two or more ports or to combine optical power from
two or more fibers into a single port.
coupling ratio
Value obtained by measuring the power at both output ports
and providing the output ratio between them. Also, CR.
crosstalk
The phenomenon of light leakage or information
transmission from one wavelength channel to an adjacent
channel, from a waveguide to an adjacent waveguide, or
from one modulated carrier frequency to another.
cutoff wavelength
For a singlemode fiber, the wavelength above which the
fiber can only support the propagation of the lowest order
transverse mode.
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