EDFA chain control: a comparison of two all-optical approaches

Abstract

EDFAs are a key technology enabler for multiwavelength optical communications, but despite their usefulness, a number of significant technological challenges remain. One which can have a large impact, particularly on wavelength routed networks, is cross saturation, i.e. the dependence of the gain in any one channel on the total input power in all channels. When the number of wavelength channels in a saturated EDFA changes, the gain in the remaining channels also changes. The resulting power excursions in the surviving channels can degrade the system performance. Among the variety of methods used to prevent this problem is all-optical gain clamping. In this paper we present the results of a time- and spectrally-resolved simulation of two version of this all-optical stabilization method to examine some of the limitations of these techniques. The model assumes a completely homogeneous gain medium and a commercially available aluminosilicate fiber pumped at 1480 nm. We assume 2 input channels for the results presented, and we drop and add one of them. The numerical results are not necessarily optimized, but can be used to develop a quantitative understanding of the behavior of these amplifier chains.