Then we present two types of sensor that we develop: elongation Fabry Perot sensor
- jointly with SCK.CEN- and Michelson type displacement sensor; they both rely on white light interferometry to retrieve the desired measurement. We report the results of irradiation of Fabry-Perot sensors in the core of BR2 material testing reactor in Mol (Belgium), under intense neutron-gamma flux and at high temperature. Six Fabry Perot fibre optics sensors are mounted on a support insensitive to radiation. The objective is to test the survival and the drift of the sensors. The temperature is maintained steady at 200ํC during 22 days then the temperature is increased up to 390ํC . Among five sensors built according to nominal scheme, four are still alive at the end of the cycle and three show a low drift of 1 to 4m. These results show a clear progress compared to the previous irradiation and make it possible to consider the use of these sensors in real tests of material in MTR reactor. However, improvement in the robustness of the interfaces is still necessary. The next part is devoted to the measurement of displacements perpendicular to the direction of the lead-in fibre, of interest for small room environments where the fibre cannot make a 90 turn. The optical scheme is based on the Michelson interferometer.