Fundamental limits on Nd/sup 3+/-doped fiber amplifier performance at 1.3 mu m

To explore the fundamental limits on performance at 1.3 mu m, a model for Nd/sup 3+/-doped fiber amplifiers which includes signal saturation and excited state absorption (ESA) at the signal wavelength has been constructed. Ignoring ESA, the difference in pump efficiency between a low-performance and a high-performance glass host is approximately=60%, indicating that ESA is the critical parameter distinguishing experimental results reported for different materials. The pump efficiency for a linear Nd/sup 3+/ amplifier is an order of magnitude less than for an Er/sup 3+/ amplifier without ESA and degrades still further with its inclusion. Applications as power amplifiers are more promising, because, in principle, high power conversion efficiencies can be obtained.<>