A two-stage erbium-doped fiber amplifier (EDFA) providing constant output power and flat gain regardless of abrupt variations of the number of channels and upstream losses is designed and fabricated by controlling each stage's pump power and mid-stage attenuation. The two-stage EDFAs were successfully applied in the 10 Gbit/s/channel WDM network with a fast link control channel having a 1.6 mu s response time to transmit one surviving channel over a 180 km DSF when 7 out of 8 channels are added/dropped. (C) 1998 Published by Elsevier Science B.V. All rights reserved.