Design and compact modeling of saturated erbium-doped fiber amplifiers with nonconfined doping

We present a theoretical and experimental study of erbium-doped fiber ampli fiers in saturated operation, examining designs in which erbium doping is d istributed throughout the core. We show the penalty due to reduced inversio n near the core boundary is negligible, while the reduced amplifier length can improve performance. We examine the accuracy of compact models for such nonconfined doping and show that a widely-used compact model exhibits subs tantial errors, while the Giles-Desurvire (G-D) model (1991. IEEE J. Lightw are Technol. 9, 271) is accurate, despite having been derived for confined erbium doping, Furthermore, we simplify the G-D model by eliminating the sa turation parameters and argue that this can improve accuracy. Finally. we e xperimentally validate the simplified G-D model for a moderately confined f iber, comparing amplifier measurements with predictions based on measured f iber parameters; measured and modeled gain and noise figure are in excellen t agreement, in the absence of adjustable parameters. (C) 2001 Academic Pre ss.