Highly efficient 978 nm dipole-pumped erbium-doped fibre amplifier with 24 dB gain

We report an Er3+-doped fibre amplifier pumped with a strained InGaAs/A lGaAs quantum-well diode laser operating at 978nm. Efficient optical coupling was achieved with a wedge-tipped fibre. An optical gain of 24dB at 1535nm was obtained with only 6.2mW of pump power, corresponding to a gain of 3.9dB/mW of pump power. This is the highest efficiency for a fiber amplifier reported to date.