The gain of erbium-doped fiber amplifiers is damaged by irradiation partly because of creation of color centers responsible of excess absorption at pump and signal wavelengths. Based on the combination of thermally stimulated luminescence and spectrophotometry, this Letter demonstrates that a part of the gain loss should be associated with the reduction of the density of Er3+ ions by irradiation.

This Letter demonstrates a remarkable interplay between photo- and radiation-induced darkening of ytterbium-doped alumino-silica optical fibers operated in amplifying conditions and harsh environments (as, e.g., in space-based applications). Influences of the pump power, ionizing dose, and dose rate on this interaction are characterized. The pump is capable of accelerating or slowing down the radiation-induced darkening build-up depending on the ionizing dose. The steady-state photo-radio-darkening level is independent of the dose and at least equal to the equilibrium level of pure photo-darkening. This lower limit is notably reached at low dose rates, including those encountered in space. We, therefore, argue that photo-resistant ytterbium-doped fibers will resist against a space mission, whatever the dose.

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.