Dynamic EDFA gain-flattening filter using two LPFGs with divided coil heaters

Abstract

We introduce a new type of dynamic erbium-doped fiber amplifier (EDFA) gain-flattening filter using two long-period fiber gratings (LPFGs) equipped with divided coil-heaters. By individually controlling each of the 64 segments of coil heaters over the grating, we adjusted the temperature distribution of LPFGs piecewise-uniformly, thus, to maintain optimum gain-flatness for different EDFA operation conditions. By controlling the different cladding modes for each LPFGs, we also achieve enhanced controllability/flexibility for the filter spectrum of dynamic LPFG. Wide dynamic-range gain/power control with less than 0.8-dB signal ripples, over 30 nm was demonstrated.