Temperature-Dependent Modeling of Cladding-Pumped Er3+/Yb3+-Codoped Fiber Amplifiers for Space Applications

In this paper, we present a multiphysics modeling of rare earth-doped cladding-pumped fiber amplifiers to predict the device performance with respect to the constraints associated with space missions. By combining the 3-D nonhomogeneous heat conduction equation with the nonlinear rate equations, the developed numerical algorithm makes possible the calculation of the spatial distribution of the different optical signals and temperature profiles. The temperature dependence of the refractive index, emission, and absorption cross sections, as well as the radiation induced attenuation and the lifetime versus the deposited dose have been considered, too. They lead to the optical signals changing inside the fiber creating a feedback loop that influences the temperature distribution within the fiber. Different operational regimes for a representative fiber design as well as different cooling configurations have been investigated. The obtained numerical results highlight that the thermal field inside the fiber could strongly deteriorate the amplifier performance especially in the space radiation environment.