Stimulated Raman crosstalk in bi-directional pumped distributed Raman amplifier for DPSK and OOK modulation format

Novel closed form formulae are derived to study crosstalk degradation due to stimulated Raman scattering (SRS) in WDM systems employing bi-directional pumped distributed Raman amplifier (DRA). They are applied to evaluate the crosstalk performance of different modulation formats, especially differential phase-shift keying (DPSK) and ON–OFF keying (OOK), which are widely used in optical communication. Further, SRS crosstalk is evaluated for different data rates and pulse shapes prevalent in optical data transmission. Next, crosstalk is calculated for different pumping schemes as special cases of bi-directional pumped DRA. The study shows that minimum SRS crosstalk can be achieved for 40 Gb/s RZ-DPSK signal with 33.3% duty cycle in WDM system employing backward pumped DRA.