During studies on the heat resources of our subsoils, particularly in geothermal energy, it is necessary to be able to characterize the distribution of temperatures along the drillings. Thus, the technology of optical fibers associated with a DTS sentry (for "Distributed Temperature Sensing") has been chosen. The physical principles, based on the amplitude and the phase shift of a laser signal to measure the temperature on a 1'000 m long optical fiber, allowed me to understand the operation of this system and to improve the accuracy of the measurements. I was able to test and validate the calibration of the device in the laboratory, and then write a protocol for its configuration. Finally, I had the opportunity to participate in geothermal field experiments to verify if aquifers could store hot water: the application of the system proved to be appropriate. Indeed, the tool allowed to measure temperatures every meter on 500 m, every 30 seconds, during 7 days continuously with an accuracy of 0,5°C. In conclusion, the accuracy of the system is highly satisfactory for its application in geothermal energy. Moreover, the use of the measurement system is simple to manage (fixed device during the whole period of the experiment) and allows a large production of spatio-temporal temperature measurements.