Thermally independent fibre optic absolute distance measurement system based on white light interferometry

A fully automated system is described that utilises white light interferometry to accurately measure the spacing between two plates. The system measures spacing in the range from 0 to 2 mm, with 5 m accuracy, at operating temperatures spanning at least 0 70 C. Results of measurements verifying this performance are presented. The system is immune from both fibre chromatic dispersion and spurious optical path differences introduced by environmental changes.