  To understand the behaviour of rocks under changing load or temperature
conditions, the determination of physical parameters like pore pressure or
temperature within the pore space is essential. Within this study, the
implementation of a novel fibre optic point sensor for pressure and temperature
determination into a high pressure / high temperature triaxial cell is
presented. For the first time, pressure was measured directly within the pore
space of a Flechtinger sandstone specimen during a hydrostatic compression test
at up to 70 MPa. The sensor used within this study consists of a miniature
all-silica fibre optic Extrinsic Fabry-Perot Interferometer (EFPI) sensor which
has an embedded Fibre Bragg Grating (FBG) reference sensor element to determine
temperature and pressure directly at the point of measurement.
