Noise performance evaluation of distributed erbium-doped fiberamplifiers with bidirectional pumping at 1.48 μm

An accurate model for unsaturated fiber amplifiers with fiber background loss is used to determine optimal parameters for distributed amplification in erbium-doped fibers. Pump power at 1.48 μm and erbium-doping levels required for transparency are studied for both unidirectional and bidirectional pumping schemes. An optimal erbium absorption coefficient which minimizes the required pump power is found. However, this case corresponds to the highest amplifier noise figure. The authors conclude that, in practice, distributed erbium-doped fiber amplifiers are not significantly advantageous compared to 980-nm-pumped lumped amplifier schemes