The flat-gain operation of a gain-shifted EDFA (GS-EDFA : 1580 nm-band EDFA) is described. The GS-EDFA provides a flat gain profile with a gain variation of < 0.2 dB for an average gain of 28 dB in the 1579-1592 nm wavelength range (13 nm). 16 channel x 10 Gbit/s WDM signals are successfully transmitted over 800 km (80 km x 10 span) of dispersion-shifted fibre using the proposed GS-EDFA with no gain equalisation or preemphasis.