This lecture covers the physics behind stimulated scatterings in nonlinear fibre optics, including Brillouin and Raman scattering. It explains the spectral characteristics, energy-momentum conservation, and mechanisms behind these phenomena. The instructor discusses the mechanisms of spontaneous inelastic scatterings, the optical effects, and the spectral characteristics of these processes. Additionally, the lecture delves into Brillouin amplifiers, the power handling capacity limitations imposed by Brillouin scattering, and the implementation of Brillouin and Raman lasers. The presentation concludes with a discussion on Brillouin Fibre Laser Gyroscopes and their applications.