spectral width 光谱宽度
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光谱宽度
FWHM Full Width Half Maximum 谱线最大宽度
定义1：光谱或光谱特性的波长范围的量度。
基于不同的光源类型，光谱宽度有几种不同的定义：
定义2：均方根谱宽（RMS）。
均方根谱宽定义为：在标准工作条件下，光谱包络分布用高斯函数P（λ）来近似。
定义3：-3dB 谱宽（FWHM）。
-3dB 谱宽定义为：在标准工作条件下，主纵模峰值波长的幅度下降一半处光谱线两点间的波长间隔，称之为FWHM 谱宽（或称-3dB 谱宽）。
(半高宽)
定义4：-20dB 谱宽。
-20dB 谱宽定义为：在标准工作条件下，主纵模峰值波长的幅度下降20dB 处光谱线两点间的波长间隔，称之为-20dB 谱宽。
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.
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.。
