Performance analysis of a concatenated erbium-doped fiber amplifier supporting four mode groups

• A concatenated amplifier supporting four mode groups is designed by cascading a central-doped EDF and an annular-doped EDF.
• We have presented a modified optimization algorithm to perform detailed investigations about this kind of amplifier.
• Design tolerances on fiber length, erbium doping radius and erbium doping concentration for each EDF are analyzed to achieve a desirable amplification performance.

An erbium-doped fiber amplifier (EDFA) supporting four mode groups has been theoretically designed by concatenating two sections of erbium-doped fibers (EDFs). Each EDF has a simple erbium doping profile for the purpose of reducing its fabrication complexity. We propose a modified genetic algorithm (GA) to provide detailed investigations on the concatenated amplifier. Both the optimal fiber length and erbium doping radius in each EDF have been found to minimize the gain difference between signal modes. Results show that the parameters of the central-doped EDF have a greater impact on the amplifier performance compared to those of the annular-doped one. We then investigate the influence of the small deviations of the erbium fiber length, doping radius and doping concentration of each EDF from their optimal values upon the amplifier performance, and discuss their design tolerances in obtaining a desirable amplification characteristics.