Аннотация
The paper describes the study of radiation-induced attenuation (RIA) spectra in reactor-irradiated single mode optical fibers (OFs) with differente high-temperature coatings (polyimyde, aluminum and copper). The OFs were previously irradiated up to fast neutron fluence 1.8·1020 n/cm2 and gamma dose 2.32 GGy. After three years of annealing at room temperature (RT), the RIA spectra were examined within the range of 650–1700 nm. All RIA mechanisms acting within this spectral range were identified: absorption bands attributed to non-bridging oxygen hole centers, a long-wavelength (LW) band with a maximum at λ > 1800 nm, and unsaturated “grey” loss due to coating microbendings or damage. It was found out that RIA asocciated with the LW band can be significantly annealed at room temperature in polyimide-coated OFs. RIA mechanisms influenced by the coating were found to be more stable than those causing LW-RIA. The LW-RIA arising during reactor and gamma irradiation exhibits a similar shape, approximated by the Kubo-Greenwood formula for alternative conductivity, which describes the absorption of self-trapped holes (STH) and exibits close thermal stability at RT. This suggests a STH-like nature of LW-RIA. The accurate approximation of the RIA spectrum in the near-infrared range requires considering contributions of the unsaturated loss or contributions of an absorption band peaking at an energy of 1.33 eV with a half-width of 0.45 eV.