Studies on Radiation Response of Optical Fibers

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Various radiation-resistant optical fibers were irradiated with 14-MeV neutrons, thermal neutrons ^<60>Co gamma-rays. The induced loss in light transmission was measured in-situ during irradiation. The radiation response of optical fibers was approximately explained by using an equation for the density of color centers related to charge trap levels in optical fibers under irradiation. Also experimental results showed there was not large difference in effects between 14-MeV neutron and ^<60>Co gamma-ray irradiations. This means that radiation response of optical fibers is influenced predominately by ionization effects closely related with dose, rather than by structural changes due to neutron displacement effects. However, response of B-doped optical fibers to thermal neutrons was different from that to other radiations. There was also large difference in the induced loss rate between thermal neutron and other irradiations. The ^<10>B (n, alpha) ^7Li reaction affects light transmission in not whole but specialized region of the optical fibers. The difference may be explained by the microscopic examination of the damage mechanism of optical fibers. This is not discussed in the present study but is an important subject in the future.