Wideband erbium-doped fibre amplifiers with three-stage amplification

Abstract
A novel three-stage amplification configuration with two intermediate gain equalisers is proposed to enlarge the bandwidth of erbium-doped fibre amplifiers. Seamless 3 dB gain bandwidths of 57 nm (1550–1607 nm) with an erbium-doped silica fibre amplifier and 62 nm (1540.5–1602.5 nm) with an erbium-doped fluoride fibre amplifier have been achieved with this configuration.