Nonlinear Photon Statistics of Pulse Amplification in Optical Fiber Amplifiers

The bit error rate (BER) in soliton amplification through a cascade of Erbium-doped fiber amplifiers (EDFA) is determined accounting for the signal-induced gain saturation. Steady state analysis under pulsed conditions is used since the level population densities respond to the time-averaged power of the soliton stream. Since shorter soliton duration is required for higher bit rates and the average soliton power increases as the duration decreases, EDFAs are operated under saturation at high bit rates. The EDFA gain and amplified spontaneous emission (ASE) noise change with the time-averaged input power and attain different values when operated under saturation than when not. In this work, the span distance and gain and noise levels are accurately determined accounting for the saturation effect in order to meet a bit error rate criteria in a given soliton communication system using a cascade of EDFAs.