Wideband, gain-flattened, erbium-doped fibre amplifiers with 3 dB bandwidths of >50 nm

3 dB bandwidths of 52 nm (1556 – 1608 nm) for a silicate erbium-doped fibre amplifier (EDFA) and 50 nm (1554 – 1604 nm) for a fluoride EDFA have been obtained by a novel scheme with two-stage erbium-doped fibres and an intermediate equaliser. Low noise figures and high pump efficiencies of the EDFAs have been confirmed.