Abstract

It has not been generally appreciated that the erbium-doped fibre amplifier¹ (EDFA) has both a saturation output power which increases with pump power, as well as an ability to operate deep in saturation without signal distortion and interchannel crosstalk². The latter is a consequence of its slow gain dynamics and is quite different from diode-amplifier behaviour³. Most investigations of the gain-characteristics of EDFAs to date have concentrated on the small input signal regime and attempted to obtain high unsaturated gain for low-pump powers^4,5, an attribute which is required for an in-line amplifier. By contrast, in this paper we discuss the application of EDFAs as power (post) amplifiers where the input signal is large and the amplifier saturation behaviour outlined above can be exploited. In the highly-saturated regime we have obtained near-quantum-limited differential pump to signal conversion efficiencies, resulting in 47mW (16.7dBm) of amplified signal for only l00mW of pump power at 978nm. Operating in this mode EDFAs are attractive for application as power amplifiers to ease power budget restrictions in point-to-point digital links, video distribution networks⁶ and LANs.

© 1990 Optical Society of America