Trade-off and design considerations of the erbium-doped fibre amplifier

The trade-off between gain efficiency and noise figure is evaluated for an optimised EDFA pumped at 980 nm. It is shown that operating at maximum gain efficiency always results in an increased noise figure well above the 3 dB quantum limit and that any attempt to reduce the amplifier noise figure results in a decrease in gain efficiency. Alternatively, for a fixed amplifier gain and pump power, increasing the fibre NA and the dopant confinement in the core reduces the amplifier NF. Finally, the input pump power required to achieve a target NF is calculated as a function of the amplifier gain, fibre NA and dopant confinement