A simple white-light fiber-optic interferometric sensing system for absolute position measurement

An absolute position-sensing system based on a white-light spectrum modulation in a very simple fiber-optic interferometer is presented. The channelled spectrum, captured by a commercial spectrometer, is analyzed using the algorithm based on fitting the calculated autocorrelation function of the captured optical power spectrum with the sum of two Gaussian functions. The absolute position is obtained directly from the separation between two fitted Gaussian functions. The system currently provides unambiguous measurement over a range of 200 μm with a minimal error of better than 6 nm.