Radiation Resistance of Single-Mode Optical Fibers at λ = 1.55 μm Under Irradiation at IVG.1M Nuclear Reactor

Radiation-induced attenuation (RIA) at a wavelength of λ = 1.55 μm as well as the RIA spectra were investigated in optical fibers during and after irradiation at the IVG.1M nuclear reactor (Republic of Kazakhstan). The fibers studied were single mode at λ = 1.55 μm, had an undoped silica core and an-F-doped silica cladding [pure-silica fibers (PSFs)], and were provided by different manufacturers. In addition to five PSFs, a single-mode revolver hollow-core fiber was also studied. The PSFs had different coating materials: polyimide, copper, or aluminum. All fibers were exposed to three runs of reactor irradiation at enhanced temperature (155-355 °C) so that by the end of the third run, the fast-neutron fluence amounted to Φ = 4.46·10
¹⁷
n/cm
²
and y-dose to D = 2.91·10
⁷
Gy. The total induced loss at λ = 1.55 μm was found to be composed of 1) RIA, 2) bending loss (BL), caused by thermal expansion of the copper cylinder the PSFs were wound on, and 3) thermo-induced microbending loss (ML) in Cu-coated PSFs. At the end of the irradiation campaign, the net RIA in PSFs proved to lie in the interval of 0.12-0.16 dB/m, which appears to be admissible to intrareactor transport fibers. It was confirmed that long-wavelength RIA tail is the only RIA origin at λ = 1.55 μm in PSFs in such strong radiation fields. The hollow-core fiber was found to feature zeroth RIA throughout the campaign.