In
telecommunications
Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...
, spectral width is the width of a
spectral band, i.e., the range of wavelengths or frequencies over which the magnitude of all
spectral component
In psychoacoustics, a pure tone is a sound with a sinusoidal waveform; that is, a sine wave of constant frequency, phase-shift, and amplitude.
By extension, in signal processing a single-frequency tone or pure tone is a purely sinusoidal signal ...
s is significant, i.e., equal to or greater than a specified fraction of the largest magnitude.
In
fiber-optic communication
Fiber-optic communication is a form of optical communication for transmitting information from one place to another by sending pulses of infrared or visible light through an optical fiber. The light is a form of carrier wave that is modul ...
applications, the usual method of specifying spectral width is the ''
full width at half maximum
In a distribution, full width at half maximum (FWHM) is the difference between the two values of the independent variable at which the dependent variable is equal to half of its maximum value. In other words, it is the width of a spectrum curve ...
'' (FWHM). This is the same convention used in
bandwidth
Bandwidth commonly refers to:
* Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range
* Bandwidth (computing), the rate of data transfer, bit rate or thr ...
, 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
The root mean square deviation (RMSD) or root mean square error (RMSE) is either one of two closely related and frequently used measures of the differences between true or predicted values on the one hand and observed values or an estimator on th ...
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.
See also
*
Spectral linewidth
A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used ...
in
optics
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...
*
Spectral bandwidth
References
*
Telecommunication theory
Optical communications
Optical quantities
Spectrum (physical sciences)
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