Gamma-rays and pulsed X-ray radiation responses of nitrogen-, germanium-doped and pure silica core optical fibers

The sensitivities of three single-mode optical fiber types were characterized under gamma(similar to1 MeV)-rays and pulsed X(similar to1 MeV)-ray radiation environments at room temperature. The radiation-induced attenuation (RIA) time dependent changes were measured at 1.55 and 1.31 mum for undoped, germanium- and nitrogen-doped core fibers. The nitrogen-doped core fiber exhibited the lowest RIA level for the time range 10(-6) to 10(+2) s after pulse and a non-linear RIA dose dependence for our tested dose range 0.01-1 kGy (SiO2). This fiber showed also a good radiation response under steady-state gamma-irradiation. The tested pure silica core fiber was the most resistant fiber under gamma-rays, but had the highest RIA levels after a pulsed X-ray one. The radiation-properties of the germanosilicate fibers depend greatly on their cladding composition. The phosphorus-codoping of these fibers suppressed their pulsed X-ray RIA peaks but was responsible for the highest permanent RIA levels after both types of irradiation. Our results showed that the two environments lead to the same RIA levels in germanosilicate and nitrogen-doped fibers, implying that the same mechanisms and color centers are involved at the different dose rates. We proposed some explanations, based on spectroscopic measurements, concerning the influence of the different tested core dopants. (C) 2003 Elsevier B.V. All rights reserved.