Effect of Radiodarkening on Optical Transmission Performance of Ytterbium-Doped Fibers

The great success of optical fibers in telecommunications today has been extended to the success of their rare-earth doped versions in medical applications, sensing technologies, high-power lasers, and amplifiers. The advantages such as excellent beam quality, high power capability, and cost-effectiveness, are increased to be widespread in high technological applications. However, exposure to ionizing radiation leads to degradation of these properties, significantly restricting the deployment of optical fibers in radiation-rich environments such as nuclear power facilities and space applications.In the present study, ytterbium-doped optical fibers were irradiated with the Co-60 gamma source using total doses of 0.5, 1, 10, and 50 kGy at a dose rate of 1.19 kGy/h. Radiation-induced attenuation (RIA) was measured at room temperature before and after irradiation. Optical transmission spectra were recorded over a broad wavelength range from 300 to 1000 nm, and RIA values at selected wavelengths (450, 560, 625, and 730 nm) were extracted. After irradiation at a total dose of 50 kGy, the formation of dopant-related color centers, including Al-OHC, POHC, and NBOHC, was observed in the optical fibers. Post-irradiation recovery behavior was monitored over periods ranging from one to three weeks. Additionally, radiation-induced variations in the refractive index of the fiber core were investigated by measuring the numerical aperture (NA) of the fibers.