It has been established that single-mode fluorosilicate light guide fibers, produced by the modified chemical vapor deposition method, dramatically decrease the radiation resistance when 1 mol % GeO2 is introduced into a silica glass core. By eliminating the impurities of chlorine and OH groups from the fluorosilicate light guide pure silica core, a low level of radiation-induced optical losses was achieved. The attenuation of the optical fibers before radiation treatment is 0.18 and 0.3 dB/km at a wavelength of 1.55 and 1.31 μm, respectively. The dependence of the optical losses of such light guide on the diameter of their bend, equal to 6 - 12 mm, was studied.

A simple design of a small cryothermostat is proposed to study the effect of gamma irradiation on optical losses of single-mode fluorosilicate light guides at a wavelength of 1.31 µm. An increase in their radiation resistance with a decrease in the test temperature from + 25 to minus 60 °C was found.