Evaluation of three different optical fibre temperature sensor types for application in gamma radiation environments

We compare the gamma radiation response of three different types of commercially available optical fibre temperature sensors. These are semiconductor absorption, Fabry-Perot cavity and fluorescence sensors. In order to evaluate their possible application in nuclear environments, we first highlight the principles of operation and the constructions. We then report on the gamma irradiation results and explain the observed degradation phenomena. For all three sensor types, the basic transduction mechanism does not seem to be affected by gamma radiation. The semiconductor absorption sensor shows a good radiation resistance (up to 160 kGy) in its present form, whereas the other sensor constructions need to be adapted. For the semiconductor absorption sensor, additional neutron irradiation experiments are performed, which are found to affect the principle of operation of this sensor.