Stimulated Raman scattering (SRS) plays a vital role as a nonlinear process in optical communication systems. As the optical signal power increases, the SRS effect grows, causing severe inter-channel crosstalk, thereby limiting the maximum power of optical signal transmission. However, judicious utilization of SRS can transform an optical fiber into a broadband Raman amplifier, offering power amplification capabilities. This chapter deeply explores into a comprehensive exploration of SRS effects in optical fibers. Firstly, the fundamental principles of Raman scattering are analyzed, with particular emphasis on the threshold conditions for Raman amplification and the Raman gain spectrum.