Analytical Model for Overmodulation in EDFAs in the Presence of ASE

We investigate the effect of ASE(Amplified Spontaneous Emission) on the gain modulation, that also referred to overmodulation. The gain modulation is the low-frequency (kHz) amplitude modulation of the EDFA pump and the communication signal used for propagating line monitoring information. We develop the model of Novak and Moesle (2002), by including ASE, that they neglected. The derivation of an analytical model, for EDFA overmodulation response, has been presented. This model provides analytical expressions for the pump and input signal overmodulation responses, respectively. These expressions describe the output signal modulation index amplitude and phase, assuming small sinusoidal steady-state oscillations of the mean pump or input signal power. In this paper we show that ASE has some effects on predictions in the high gain/low saturation regime.