Photon shot noise is the ultimate limit on SNR measurements of optical information. It thus represents the ultimate limit as well for an ideal FT-IR spectrometer. Calculation of this limiting performance is useful in evaluation of the performance of existing real instruments.
T. Hirschfeld, "Ideal FT-IR Spectrometers and the Efficiency of Real Instruments," Appl. Spectrosc. 40, 1239-1240 (1986)