[en] Photon beams produced by a cobalt-60 Unit and a 6 MV linear accelerator equipped with stereotactic collimators were used to investigate some dosimetric properties of a radioluminescent dosimeter based on a Ce-doped optical fibre. The stability of the signal with increasing the irradiation time, enabled a reliable and real-time measurement of the dose rate. The methods, recently developed, of optical coupling, light collection and signal processing allowed to achieve a satisfactory signal to noise ratio, a good reproducibility and a linear dose-response. The punctual dimension of the doped fibre diameter was exploited in the characterization of stereotactic fields, providing results in agreement with those obtained using a micro-ionization chamber