Optimization Algorithm Applied to the Design of Few-Mode Erbium Doped Fiber Amplifier for Modal and Spectral Gain Equalization

Abstract

Gradient descent optimization algorithm is applied to design few-mode Er $^{3+}$ -doped fibers adapted to gain equalization over modes and wavelengths, for mode division multiplexing. Theoretical study is performed for fiber designs supporting six and ten spatial modes at signal wavelength. Flat gain is obtained by optimizing Er $^{3+}$ doping profile of a micro-structured core and modal composition of the pump beam.