IMPROVED PROBE GEOMETRY FOR FLUORESCENCE-BASED FIBEROPTIC TEMPERATURESENSOR

A fluorescent fibre probe with high collection efficiency for fluoresc ence-lifetime measurements is presented. A numerical model for calcula ting the collection efficiency for different probe designs has been em ployed. The position and number of fibres, crystal geometry, crystal-f ibre gap and the backside crystal reflectivity are used as evaluation parameters for probe optimization. A possible three-fold increase in c ollected fluorescent light intensity is predicted in comparison with t he classical two-fibre configuration. The model has been confirmed by constructing a seven-fibre probe with alexandrite crystal as the sensi ng element. An accuracy of +/- 0.3 K is achieved in the 20-90 degrees C temperature range.