Optimization of the Design of High Power $\hbox {Er}^{3+}/\hbox {Yb}^{3+}$ -Codoped Fiber Amplifiers for Space Missions by Means of Particle Swarm Approach

In this paper, the optimization of the design of rare earth-doped cladding-pumped fiber amplifiers is investigated to improve their performance with respect to the constraints associated with space missions. This work is carried out by means of a computer code based on particle swarm optimization (PSO) and rate equation model. We consider a fiber that is radiation tolerant at the space dose levels, and we characterize the radiation response of the amplifier based on it. By simulations, we study how the design of the radiation-tolerant double-cladding Er³⁺/Yb³⁺-codoped fiber amplifiers (EYDFAs) can improve the global system response in space. The rate equations model includes the first and secondary energy transfer between Yb³⁺ and Er³⁺, the amplified spontaneous emission and the most relevant upconversion and cross relaxation mechanism among the Er³⁺ ions. The obtained results highlight that the developed PSO algorithm is an efficient and reliable tool to perform the recovering of the most relevant spectroscopic parameters and the optimum design of this kind of devices. These results demonstrated that the performance of high power optical amplifiers can be optimized through such a coupled approach, opening the way for the design of radiation-hardened devices for the most challenging future space missions.