D-EDFA have their signal gain distributed over long fiber lengths. This paper deals with gain and noise figure characteristics at 150dB/km Rayleigh constant of a forward, and bidirectional pumped distributed EDFAs, operating in 1550 nm as a function of fiber length, Erbium ion density, injected pump power and signal input power. These studies are done by using optiystem 6.0 software simulation (optical
amplifier and communication system design software) at bit rate of 2.5 Gbps