The Implications of Fluctuation Noise in Multiplex Spectroscopy

The signal/noise ratio of a scanning spectrometer in the spectral region where shot noise is not limiting (sub-stantially the λ ≥ 1 μ region of the infrared spectrum) can be expressed as [Equation 1] where SNRsc(ν) is the signal/noise ratio as a function of ν, f(ν) is the spectral density function of the spectrum measured at resolution Δν, a is the noise equivalent power of the detector, b is the relative fluctuation amplitude of fluctuations in the source, sample, or measuring system, T is the total measurement time, and ν1, ν2 the scan limits.