Stimulated Raman crosstalk in WDM system employing distributed Raman amplifier for DPSK and OOK modulation format

Abstract

Novel closed form formulae are derived to study crosstalk degradation due to stimulated Raman scattering (SRS) in WDM systems employing multi-span bi-directional pumped distributed Raman amplifier (DRA). The formulae are used to evaluate the crosstalk performance of differential phase-shift keying (DPSK) and ON-OFF keying (OOK) modulation format which are widely used in optical communication. SRS crosstalk is further evaluated for different data rates and pulse shapes prevalent in optical data transmission. Next, crosstalk is calculated for different pumping schemes by taking into account the launched power 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.