Dual feedback loop power control in an optical fibre amplifier

摘要

An automatic power controlling device can stabilise the output of an optical erbium doped fibre amplifier (EDFA) 506 by selecting either a first feedback control loop, using an output photodiode 516, or a second feedback control loop, using a photodiode 514 provided in the pump laser diode 532. The optical excitation signal output from the pump laser diode 532 is thereby controlled on the basis of the intensity of the optical signal detected through the selected feedback control loop. The feedback loop to be used is selected on the basis of the current flowing through the pump laser diode 532. The control process may be either analogue or digital.