EDFA gain equalization with fiber filter for WDM systems

Abstract

Erbium doped fiber amplifiers can achieve a high gain over more than 40nm bandwidth. However, they suffer from a non uniformity of the gain, and this is particularly detrimental to WDM applications. As they propagate through a chain of EDFAs, the channels at different wavelengths will accumulate increasing discrepancies between them in terms of gain and SNR. In order to make it possible to chain EDFAs in a WDM environment, the EDFAs should have ideally both a flattened gain and SNR. A method as proposed in [1] and [2] admittedly cannot achieve equalization of both gain and SNR. On the other hand, some EDFAs are optimized for WDM by adjusting the characteristic and length of the fiber and the pump power [3], but in that case they usually show a flattened gain for a small range of input power. © 1995 Optical Society of America