Material dispersion coefficient
Encyclopedia
In an optical fiber
, the material dispersion coefficient, M(λ), characterizes the amount of pulse broadening by material dispersion
per unit length of fiber and per unit of spectral width
. It is usually expressed in picosecond
s per (nanometre
·kilometre
).
For many optical fiber materials, M(λ) approaches zero at a specific wavelength
λ0 between 1.3 and 1.5 μm. At wavelengths shorter than λ0, M(λ) is negative and increases with wavelength; at wavelengths longer than λ0, M(λ) is positive and decreases with wavelength.
Pulse broadening caused by material dispersion in a unit length of optical fiber is given by the product of M(λ) and spectral width
(Δλ).
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
, the material dispersion coefficient, M(λ), characterizes the amount of pulse broadening by material dispersion
Dispersion (optics)
In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency, or alternatively when the group velocity depends on the frequency.Media having such a property are termed dispersive media...
per unit length of fiber and per unit of spectral width
Spectral width
In telecommunications, spectral width is the wavelength interval over which the magnitude of all spectral components is equal to or greater than a specified fraction of the magnitude of the component having the maximum value....
. It is usually expressed in picosecond
Picosecond
A picosecond is 10−12 of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to 31,700 years....
s per (nanometre
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
·kilometre
Kilometre
The kilometre is a unit of length in the metric system, equal to one thousand metres and is therefore exactly equal to the distance travelled by light in free space in of a second...
).
For many optical fiber materials, M(λ) approaches zero at a specific wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
λ0 between 1.3 and 1.5 μm. At wavelengths shorter than λ0, M(λ) is negative and increases with wavelength; at wavelengths longer than λ0, M(λ) is positive and decreases with wavelength.
Pulse broadening caused by material dispersion in a unit length of optical fiber is given by the product of M(λ) and spectral width
Spectral width
In telecommunications, spectral width is the wavelength interval over which the magnitude of all spectral components is equal to or greater than a specified fraction of the magnitude of the component having the maximum value....
(Δλ).