Abstract

In a ultra-long system with cascaded erbium-doped fiber amplifiers⁽¹⁾ (EDFAs), in order to keep a signal-to-noise ratio (SNR) as high as possible, EDFA⁽²⁾ having high output power and low noise is highly required as a post-amplifier or as an in-line-amplifier. Such an EDFA is also important for optical pre-amplifiers with large dynamic ranges. Although Way et al. reported a low noise figure (NF) in a saturation region under the condition of sufficiently high pump power⁽³⁾, the relationship between lowering the NF and optimizing the gain of EDFA was not clear. In this paper, we report that an EDFA having both a high output power (+15dBm) and a low NF (6dB) can actually be realized using 1.48μm pump LDs when the EDFA length is optimized to give a maximum gain for large signal power. In addition, we also show that there is a remarkable difference between forward and backward pump in terms of NF characteristics of EDFA in a deep saturation.

© 1991 Optical Society of America