Mode-Dependent Gain Characteristic of Bent Coupled Multi-Core EDFA

We investigated the impact of varying the structural parameters, the bending and twisting conditions on the mode-dependent gain (MDG) in a coupled-multi-core erbium-doped fiber amplifier (C-MC-EDFA). We experimentally confirmed the differences in the MDG of the C-MC-EDFA between bent and straight conditions. We then numerically discuss the MDG dependency on the core pitch and bending radius of MC-EDF by using the core localization factors of the super-modes. The results show that the MDG greatly deteriorates for the C-MC-EDFA with a smaller core pitch in a straight condition, whereas it can be reduced by applying appropriate bending. We finally show the feasibility of the designing C-MC-EDFA with MDG lower than 0.1 dB by using the optimized bending radius, which is useful when designing C-MC-EDF with higher core density.