Coupled Experiment/Simulation Approach forthe Design of Radiation-Hardened Rare-EarthDoped Optical Fibers and Amplifiers

We developed an approach to design radiation hardened rare earth -doped fibers and amplifiers. Thismethodology combines testing experiments on these devices withparticle swarm optimization (PSO) calculations. The compositionof Er/Yb-doped phosphosilicate fibers was improved by introducing Cerium inside their cores. Such composition strongly reduces the amplifier radiation sensitivity, limiting itsdegradation: we observed a gain decreasing from 19 dB to 18 dBafter 50 krad whereas previous studies reported higher degradations up to 0°dB at such doses. PSO calculations, taking only into account the radiation effects on the absorptionefficiency around the pump and emission wavelengths, correctlyreproduce the general trends of experimental results. Thiscalculation tool has been used to study the influence of theamplifier design on its radiation response. The fiber length usedto ensure the optimal amplification before irradiation may berather defined and adjusted to optimize the amplifierperformance over the whole space mission profile rather thanbefore integration in the harsh environments. Both forward andbackward pumping schemes lead to the same kind of degradationwith our active fibers. By using this promising coupled approach,radiation-hardened amplifiers nearly insensitive to radiationsmay be designed in the future.