We have investigated the thermoluminescent response of three Germanium-doped silica-based optical fibers obtained by varying the drawing parameters from a unique preform. We compared under X-ray irradiation, their dosimetric properties to those of two widely used commercial dosimeters based on different technologies. Then, we investigated the potential of these optical fibers to monitor gamma rays at different doses and dose-rates, and to different fluences of particles (0.8 and 14 MeV neutrons and 63 MeV protons). Our results show that the thermoluminescence response of the Ge-doped optical fibers depends linearly on the direct ionizing dose (gamma-, X-rays) or on the indirect ionizing dose (protons, neutrons). As a consequence, this class of fibers is an excellent candidate for passive dosimetry in various fields from medical applications to high-energy physics.