Transient gain dynamics in wide bandwidth discrete Raman amplifiers

Abstract

This paper has described measurements of transient gain effects caused by dropping channels in a wide bandwidth backward pumped discrete Raman amplifier. These measurements have shown that in a WDM amplifier the transients include two different features. There is a small but fast component due to signal-to-signal Raman crosstalk which can either increase or decrease the signal power depending on whether the surviving channels are at a longer or shorter wavelength than the dropped channels. There is also a larger, slower component due to pump readjustment which occurs on a time scale determined by the length of the amplifier. After changing the signal power at the input to the amplifier it requires up to three times the transit time of the amplifier for the new steady state to be reached.