Spectral width
Encyclopedia
In telecommunication
s, spectral width is the wavelength
interval over which the magnitude of all spectral component
s is equal to or greater than a specified fraction of the magnitude of the component having the maximum value.
In optical communications
applications, the usual method of specifying spectral width is the full width at half maximum
. This is the same convention used in bandwidth, defined as the frequency range where power drops by less than half (at most −3 dB).
The FWHM method may be difficult to apply when the spectrum has a complex shape. Another method of specifying spectral width is a special case of root-mean-square deviation
where the independent variable is wavelength, λ, and f (λ) is a suitable radiometric quantity.
The relative spectral width, Δλ/λ, is frequently used where Δλ is obtained according to note 1, and λ is the center wavelength.
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
s, spectral width is the 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...
interval over which the magnitude of all spectral component
Spectral component
In telecommunications, spectral component is any of the waves that range outside the interval of frequencies assigned to a signal. Any waveform can be disassembled into its spectral components by Fourier analysis or Fourier transformation...
s is equal to or greater than a specified fraction of the magnitude of the component having the maximum value.
In optical communications
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
applications, the usual method of specifying spectral width is the full width at half maximum
Full width at half maximum
Full width at half maximum is an expression of the extent of a function, given by the difference between the two extreme values of the independent variable at which the dependent variable is equal to half of its maximum value....
. This is the same convention used in bandwidth, defined as the frequency range where power drops by less than half (at most −3 dB).
The FWHM method may be difficult to apply when the spectrum has a complex shape. Another method of specifying spectral width is a special case of root-mean-square deviation
Root mean square
In mathematics, the root mean square , also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids...
where the independent variable is wavelength, λ, and f (λ) is a suitable radiometric quantity.
The relative spectral width, Δλ/λ, is frequently used where Δλ is obtained according to note 1, and λ is the center wavelength.