The impact of power transients stemming from channel reconfiguration on erbium-doped fiber amplifier (EDFA) gain dynamics in wavelength division multiplexing (WDM) optical networks is investigated. The impact of power transients on EDFA gain dynamics leads to error bursts and impact on the network performance. First, we model an EDFA simulator with one-dimensional nonlinear differential equation that describes the time-dependent population density. For the model to show gain flattening multiplexed channels at different wavelengths, new function blocks are used. Next, to simulate the noise performance of EDFA, forward amplified spontaneous emission noise blocks are designed that add noise dynamically at signal wavelength. Finally, EDFA simulator is used as an in-line amplifier for amplitude shift keying-modulated WDM fiber communication link where the gain clamping facility is provided to protect power imbalance at the receiver. Next, we apply the mentioned model in the estimation on the link performance parameters, like signal-to-noise ratio and bit error rate, and variations in these values by channel add/drop results from variation in incremented signal output of EDFA. The variations are almost equal at different wavelengths in C- or L-band, which is due to flat gain and also the gain clamping facility of the present EDFA simulator.