Low-noise extended L-band phosphorus co-doped silicate EDFA consisting of novel two-stage gain-flattened gain blocks

A novel low-noise extended L-band silicate erbium-doped fibre amplifier (EDFA) is proposed, consisting of two novel gain-flattened gain blocks for wavelength-division multiplexing (WDM) signals from 1562.2 to 1619.6 nm. Each gain block consists of three isolated phosphorus/alumina co-doped silicate EDFs, an intermediate embedded gain flattening filter (GFF), a short wavelength pump laser diode, and a pump bypass and/or a recycle path. The proposed EDFA, which uses only three pump laser diodes, has achieved noise figures as much as 6.1 dB lower than those realised by an earlier EDFA, when its intermediate optical attenuator has large signal losses and the input signal power is low.