Design and modeling of laser-controlled erbium-doped fiber amplifiers

This paper presents a comprehensive theoretical analysis of erbium-doped fiber amplifiers (EDFAs) which use lasing to achieve automatic gain control. We have derived, for the first time, the explicit analytical expressions for the calculation of optical gain and noise spectra, critical input signal power, and optimum amplifier length for the laser-controlled EDFAs. Based on these expressions, the design of this type of EDFA becomes a simple and straight-forward task. Two amplifier design criteria, one maximizing the critical input signal power and the other optimizing gain spectra flatness, are discussed. Two examples are given to illustrate the design of gain controlled amplifiers with maximum critical input power and optimum gain spectra flatness, respectively