Non-linear integral control of photon power transients in optical communication networks with erbiumdoped fibre amplifiers

In this study the authors present a novel technique for control of signal power transients caused by signal add/drops in optical communication networks with erbium-doped fibre amplifiers (EDFAs). The approach utilises the electronic automatic gain control that combines both feedback and feedforward control of EDFA. Feedback control is non-linear integral control and feedforward control is a steady-state gain scheduling technique. The feedback non-linear control requires information about the average inversion level that is obtained via a simple linearised first-order observer. The scheduling variable used is the nominal pump power needed to keep the average inversion level at the desired value at steady state and the input signal powers given at particular wavelengths. In the simplified gain scheduling version, the scheduling variable is the total input signal power. Simulation examples indicate that the proposed controller completely eliminates at steady state the photon power transients caused by signal add/drops with the steady state being reached within a few milliseconds.