Investigation of the radiation response of optical fibers induced by pulsed ionizing radiation

Abstract

We have studied the radiation response of a single-mode optical fiber under the influence of pulsed photon and gamma-neutron radiation. The recovery time of the characteristics of the same optical fiber for one dose per pulse can vary within a wide range from a few milliseconds to several seconds, depending on various influencing factors. It is for the first time that we have experimentally recorded an increase of radiation-induced attenuation (RIA) of an optical fiber in the short-wavelength region after exposure to a pulsed neutron flux, simultaneously with RIA decrease in the long-wavelength region after the end of exposure and a subsequent RIA decrease in the entire studied wavelength range. This may mean a reversible rearrangement of the glass structure of the optical fiber. The RIA curves of the optical fibers under the influence of pulsed ionizing radiation are analyzed using the approaches of chemical kinetics. It has been established that the reaction order of the relaxation processes of short-lived radiation-induced color centers (RTCs) is fractional, which indicates a complex, possibly multi-stage process. After a few microseconds after exposure, all relaxation processes are in the diffusion region. The paper is the first to show that the characteristic RTCs relaxation time is directly related not only to temperature but also to the level of the stress-strain state of the optical fiber, and for an optical fiber with a pure-silica core, it is additionally related to the input optical power.