Chirping introduced into a Michelson interferometer permits correction for nonlinearities, distortion, and intermodulation in the final spectrum. This is because the false harmonics of each frequency carry the characteristic phase of the original frequency, whereas true spectral components at higher frequencies have their own characteristic phase. In an unchirped interferogram, there is no such distinguishing phase. This paper explains how the distinguishing phase occurs, presents two algorithms for carrying out the distortion correction when the form of the distortion is known, and displays results of correcting selected distorted experimental interferograms. This capability is a new advantage of chirping in Fourier spectroscopy.
Thomas P. Sheahen, "Use of chirping to compensate for nonlinearities in Fourier spectroscopy," J. Opt. Soc. Am. 64, 485-494 (1974)