Abstract: Systems and methods for performing optical annealing of an optical fiber disposed in a cryogenic environment subject to ionizing radiation, such as in a fusion energy source, are provided. The techniques include optically annealing the optical fiber using first light having a first peak wavelength and second light having a second peak wavelength different than the first peak wavelength. The first and second peak wavelengths may be selected to optically anneal defects associated with transient radiation-induced attenuation (RIA) and permanent RIA.