Irradiation of Multimode Ge-doped and F-doped Optical Fibers at Cryogenic Temperatures Down to 10 K

The combined effect of radiation and cryogenic temperatures on the response of two different multimode fibers (MMF), one conventional and one radiation resistant, has been investigated. This article presents the outcome of the measurements of the radiation induced attenuation (RIA) in those fibers at 830 nm and 1310 nm under gamma irradiation and at temperatures of 300 K, 218 K, 143 K and 10. The results reveal a strong increase of the RIA when decreasing the temperature down to cryogenic levels, with substantial different growth dynamics between the two fibers. However, both cases show a non-linear dependence of the RIA on the temperature. It is also observed that after a long recovery time, including the heating of the fiber from cryogenic temperature to room temperature, a large amount of the defects created are annealed, bringing the radiation resistant fiber close to its initial performance.