Component position measurement through polymer material by broadband absolute distance interferometry

We describe the development of a fibre optic system using absolute distance interferometry for application to long-term monitoring of component positions. Initially we demonstrate the operation of a single probe in air with a distance resolution of 8 nm and an absolute displacement accuracy of 0.08% over relatively short baselines of up to a few mm. The technique is then developed to measure distance through a transparent polymer. Our in situ method utilizes a dual probe arrangement to measure optical path length and refractive index simultaneously. © British Crown Copyright 2005/MOD.