PROPAGATION OF SIGNAL AND NOISE IN CONCATENATED ERBIUM-DOPED FIBER OPTICAL AMPLIFIERS

Signal propagation and noise accumulation in lightwave systems using saturated optical amplifiers as repeaters are analyzed. Numerical simulations of amplified spontaneous emission in concatenated erbium-doped fiber amplifers indicate that a reach beyond 10 000 km is possible with a 1.55 mu-m system in the absence of fiber nonlinearities. Distributed optical amplifiers are shown to have low noise, but require higher pump power than lumped amplifers. Three operating modes of an amplifier lightwave system are identified and their relative signal power efficiency and noise performance are described.