Gain Dynamics of Few-Mode Erbium-Doped Fiber Amplifier

A model describing the dynamic behavior of a few-mode erbium-doped fiber amplifier (FM-EDFA) is derived using the average inversion level. In that model, when the amplification overlap factor and equivalent area are independent of time, the dynamic behavior of an FM-EDFA is described by a differential equation of the average inversion level. This condition is satisfied for an FM-EDFA with a ring-core erbium-doped fiber (EDF). The derived model is validated in simulations and experiments of transient and frequency responses of a 2-LP mode EDFA with a ring-core EDF.