Reactor radiation-induced attenuation in fused silica optical fibers heated up to 1000 °c

The goal of this work was to experimentally determine the performance of commercially available fused silica optical fibers, particularly at the wavelengths used in commercial optical instrumentation (850, 1300, and 1550 nm), as they are simultaneously subjected to reactor radiation and heated to temperatures up to 1000 °C. For that, the broadband (400-2000 nm) optical attenuation in 10 meter lengths of low-OH and high-OH multimode fused silica fibers was continuously monitored in-situ. This work presents the first in-situ measurements of reactor radiation-induced attenuation in fused silica as a function of temperature. Results showed that, for the wavelengths monitored in this experiment, the spectral features of the reactor radiation-induced attenuation are similar to those obtained from a previous high temperature (up to 600 °C) Co-60 gamma irradiation experiment. Both radiation environments were found to primarily affect wavelengths below 1200 nm and 800 nm in the low-OH and high-OH fibers, respectively. The radiation-induced attenuation generally decreased with increasing temperature. However, thermally-induced attenuation caused increases in attenuation unrelated to radiation damage when the low-OH and high-OH fibers were heated during irradiation to temperatures at or above 400 and 800 °C, respectively. At the end of the reactor irradiation at 600 °C, the added attenuation in the low-OH fiber at 1550 nm and the high-OH fiber at 850 nm were as low as 0.04 and 0.02 dB/m, respectively. The results of this work suggest that silica optical fibers are excellent candidates for light transmission at 850 nm (using high-OH fibers), and at 1550 nm (using low-OH fibers) under the high temperature irradiation conditions tested in this work.