Effect of ASE on the gain modulation in EDFAs

We investigate the effect of ASE on the gain modulation, referred to also as 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 amplified spontaneous emission (ASE), that they neglected it. The derivation of an analytical model for EDFA overmodulation response has been presented. This model provide 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 have some effect on predictions in the high gain/low saturation regime.