Fibre optic broadband interferometry for absolute distance measurements through optically dense media

In this paper we describe absolute distance measurement through an optically dense transparent polymer, using a fibrebased, broadband interrogated, Fabry-Perot interferometer. The dual fibre sensor demonstrates a system that provides 'on-line' compensation for temperature and stress effects through recovery of refractive index information. Over a typical sensing range of 1mm distance measurements with sub-micron accuracy are reported.