Optimal bidirectional Raman pumping in dispersion-shifted fibres for WDM inter-channel FWM reduction

Bidirectional Raman pumping schemes for C-band dense-WDM transmission in dispersion-shifted fibres are experimentally investigated taking into account both pump-to-signal and inter-channel four wave mixing (FWM) interactions, as well as optical signal-to-noise ratio (OSNR) performance. For the first time it is shown that an optimal combination of co- and counter-propagating pumping technologies leads to acceptable OSNR performance allowing, at the same time, for an effective reduction of inter-channel FWM crosstalk with limited pump-to-signal FWM interaction.