This document discusses the effect of stimulated Raman scattering (SRS) in a wavelength division multiplexing (WDM) optical fiber communication system. It describes how SRS non-linearly transfers energy between optical signals in the fiber, causing power to be transferred from lower to higher wavelength channels. This results in signal distortion at the receiver. The document presents a simulation of a 40-channel WDM system using OptiSystem software. It shows how increasing the input power leads to greater power tilt and channel steepening due to SRS. This degrades the optical signal-to-noise ratio and increases the bit error rate, demonstrating that SRS negatively impacts WDM system performance.