A 100 m deep borehole in mountain permafrost hasbeen equipped with both a thermistor chain and a fiber optic cable for DTS measurements. The device permits to assess the resolution and accuracy of DTS measurements through the comparison of parallel DTS profils and with classical sensors. First results show a reolution in the order of 0.1 °C can be achieved, but that the accuracy is strongly dependent on the calibration of the measurement.