Analysis of the frequency components of phase-modulated white light interferometry to determine the central maximum position

A detailed theoretical analysis with numerical calculations was conducted to study the frequency spectrum resulting from the application of a sinusoidal phase modulation to a two beam interferometer illuminated by a low coherence source with a Gaussian spectral profile. Results of these calculations shows behavior of the frequency components which was unexpected from earlier derivations of the frequency spectrum. The results of the calculations have been experimentally confirmed using an all-fiber interferometer illuminated by a source with a Gaussian spectral profile. The results are useful for the signal processing of tandem interferometers for 'white light' interferometry.