Optimal design of L-band EDFAs with high-loss inter-stage elements

Abstract

In this paper, we theoretically investigate and optimize a multi-stage L-band EDFA including high-loss inter-stage element based on a reliable numerical model. Influences of inter-stage element as well as stage length on the amplification performance of different pumping schemes are analyzed and compared. The results show that a piece of unpumped Erbium doped fiber (EDF) should be placed before (forward pumping) or after (backward pumping) the loss element to improve the pump efficiency through ASE re-absorption, and by optimizing the EDF length of each stage properly, both high-output gain and uniform NF profile can be derived even with high-loss inter-stage devices. After optimization, only 2.4 dB gain decrease and 1.4 dB NF increase are obtained with up to 12 dB inter-stage attenuation by using a four-stage architecture, and dual-forward pumping scheme can have almost the same characteristics as forward–backward pumping. Moreover, we also consider the impact of pump adjustment on the noise performance of L-band EDFAs with inter-stage loss in case of channel add/drop, and some useful guidelines are obtained.