Gain-flattened L-band erbium-doped fibre amplifier using dual-core fibre

We show that an L-band EDFA can be constructed from a dual-core fibre with flat gain over the wavelength range 1565 nm to 1615 nm. The gain variation within the range is 0.6 dB and its noise figure is 3.9 dB at 980 nm pump power of 60 mW. The fibre has two cores, one doped with erbium and the other undoped. The feature of this amplifier is its simplicity: only a length of dual core fibre. There is no need for gain-equalization filters nor multiple pump sources. Furthermore, this amplifier can be combined with the dual-core C-band amplifier to form a very wide band dual-core fibre amplifier with very flat gain throughout.