A theoretical analysis of amplification characteristics of bi-directional erbium-doped fiber amplifiers with single erbium-doped fiber

Based on the discussion of the structure scheme of bi-directional EDFA (Bi-EDFA) with single erbium-doped fiber (EDF) which can efficiently suppress the internal reflections, a rate equation model for the Bi-EDFA is developed to calculate the signal gain, pump absorption and output noise spectrum. The effects of numbers of signals, pumps of arbitrary direction, amplified spontaneous emission (ASE) and inherent loss are taken into account. Using this model, the influence of EDF length, input signal power, pump style and pump power on the gain characteristics of the Bi-EDFA is analyzed. The forward and the backward noise figures versus bi-directional input signal power for different pump styles are also investigated. With these results, the optimal design for Bi-EDFAs in optical fiber communication systems and networks can be achieved. (C) 1999 Elsevier Science B.V. All rights reserved.