Pump wavelength optimisation of erbium-doped fibre amplifier in 800 nm band

The absorption band centred around 805 nm suffers from two excited state absorption (ESA) bands which peak, respectively, at 790 nm. The difficulty in comparing the pump wavelength efficiencies comes from the fact that the optimum amplifier length depends not only on pump power but also on pump wavelength. It is shown that for high pump powers, pumping around 820 nm is most efficient, however for lower pump powers shorter wavelengths provide the highest gains.