Analysis of transient gain saturation and recovery in erbium-dopedfiber amplifiers

An analysis of transient gain dynamics in erbium-doped fiber amplifiers is presented to provide a qualitative explanation of its time constants. The theory yields analytical solutions at the fiber amplifier input end, making it convenient to study the time dependence of gain saturation and recovery under changing input signal conditions. It is shown that, independently of the pump wavelength, gain saturation and recovery effects have long characteristic times (0.2-10.0 ms) which advantageously reduce saturation-induced crosstalk in the amplifier. The effect of saturation-induced gain modulation is found to vanish at signal frequencies above F=1 kHz, which is in good agreement with observed experimental results