The Effects of Complex Energy Transfer Dynamics and Gaussian Profiles on the Performance of High-Concentration EDFAs

In this paper, we investigate the effects of complex energy transfer dynamics and Gaussian profiles on the gain and noise figure performance of erbium-doped fiber amplifiers (EDFAs) with high doping concentration. We use a two-level system to study the complex energy transfer dynamics that comes from the homogeneous up-conversion (HUC) and the pair-induced quenching (PIQ). In our model, the system is stimulated by a pump source at the wavelength of 1480 nm and operated with a signal source at the wavelength of 1560 nm. Assuming a uniform distribution of erbium ions in the fiber core, we approximate the fundamental mode distributions by Gaussian profiles which are commonly used to calculate the mode radius or spot size. Using the numerical calculations and analysis of the rate and power propagation equations for a two-level model under consideration, the most advantageous Gaussian profile is determined as the Whitley mode radius to obtain a high-gain and a low-noise figure per unit length of silica-based fiber amplifiers. The effects of the number of ions per cluster and the percentage of ions in clusters on the calculated gain and noise figure are compared for several pump powers. Results are discussed to achieve a desired gain and noise figure performance, and compared with the available experimental data to verify the feasibility of the model.