Temperature measurement using rare earth doped fibre fluorescence

Optical fibre sensors have been developed to measure a wide range of parameters and in many circumstances show significant advantages over conventional measurement techniques. This thesis investigates a relatively new method of measuring temperature using optical fibres, known as the fluorescence intensity ratio technique. The fluorescence intensity ratio technique uses the thermal coupling of two closely spaced energy levels in an ion. When populated the relative number of ions, and hence the intensity of fluorescence from each of the two closely spaced levels, follow a Boltzmann distribution. Measurements of the fluorescence intensity originating from the two levels can therefore be used to determine temperature. The fluorescence intensity ratio was studied using six different rare earth ions, doped into a variety of glasses and crystals to investigate the feasibility of developing an accurate, low cost temperature sensor