Analysis of stimulated Raman scattering on an optical WDM communication system considering chromatic dispersion

Abstract

Optical communication utilizes the huge potential bandwidth of fiber through the use of Wavelength Division Multiplexing (WDM). However, the performance of an optical WDM communication system is degraded by fiber attenuation, chromatic dispersion, nonlinear effects including Stimulated Raman Scattering (SRS), stimulated Brillouin scattering, four wave mixing, self- and cross-phase modulation. In this research work the effect of SRS on the performance of an optical WDM system is studied in presence of chromatic dispersion. The SRS effect occurs at high power level and is observed to cause the amplification of longer wavelength channels at the expense of shorter wavelength channels in the WDM system. In this way the effect limits the maximum transmitter power that can be launched maintaining a given system performance. The allowable transmitter power is found to decrease with increase in' the number of channels. The performance evaluation is done using the triangular model of Raman gain, which is being well-employed in the literature. However, this model gives inaccurate results if we consider a wideband WDM system. Therefore, an improved model for the Raman gain is employed to evaluate more accurately the transmitter power limitations including the SRS effect from all the channels in the wideband WDM system. Fiber chromatic dispersion causes phase delay among the propagating pulses. Thus it is observed to reduce the probability of power transfer from shorter to longer wavelength channels by the SRS effect. The effect of chromatic dispersion on the phenomenon of SRS interaction is evaluated in terms of the walk off length, which is defined as the length after which a pulse gets dispersed by a time duration of bit period. The SRS limitations on the system performance are investigated for different chromatic dispersion parameters and bit rates.