Precision of frequency scanning interferometry distance measurements in the presence of noise

A lower limit-the Cramer-Rao bound-on the variance of frequency scanning interferometry (FSI) distance measurements in the presence of noise is presented. We show that, with a suitable analysis method, the variance of experimental measurements almost reaches this limit. In particular, the variance of results with a simple analysis method was 1.54 times the limit over a range of signal-to-noise ratios. This bound aids the understanding of FSI distance measurement uncertainty, and provides a benchmark against which to compare FSI analysis algorithms.