We investigated point defects induced in rad-hard Fluorine-doped optical fibers using both a mixed source of neutrons (fluences from 1015 to 1017 n/cm2) and γ-rays (doses from 0.02 to 2 MGy) and by a γ-ray source (dose up to 10 MGy). By combining several complementary spectroscopic techniques such as radiation-induced attenuation, confocal micro-luminescence, time-resolved photo-luminescence and electron paramagnetic resonance, we evidenced intrinsic and hydrogen-related defects. The comparison between the two irradiation sources highlights\ud close similarities among the spectroscopic properties of the induced defects and the linear correlation of their concentration up to 1016 n/cm2. These results are interpreted on the basis of the generation processes of defects from precursors sites, that are common to both γ-rays and neutrons. In contrast, the highest neutron fluence (1017 n/cm2) causes peculiar effects, such as the growth of a photoluminescence and variations of the spectral and decay properties of the emission related with nonbridging oxygen hole centers, that are likely due to silica network modification

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We report the study of a radiation resistant single mode optical fiber doped with fluorine exposed to mixed neutron and gamma-radiation up to 10(17) n/cm(2) fluence and >2 MGy dose to evaluate its performances when used as the sensing element of a distributed Optical Frequency Domain Reflectometry (OFDR). The use of complementary spectroscopic techniques highlights some differences between the responses of solely gamma-radiation (10 MGy) or mixed neutron and. (10(17) n/cm2 + >2 MGy) irradiated samples. Those differences are linked to the defect generation rather than to structural changes of the a-SiO2 host matrix. We show that a modification of the refractive index of similar to 10(-5) is induced at the highest investigated neutron fluence. However, the feasibility of distributed temperature measurements along the irradiated fiber is demonstrated with an accuracy of 0.1 degrees C over a sensing length up to similar to 130 m with the tested OBR4600 interrogator. These results are very promising for the integration of OFDR sensors in mixed neutron and gamma radiation environments

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