Nowadays, fibre optic sensors have been widely used to detect temperature, pressure, vibration and other physical properties. To design high performance fibre optics sensors, sensing elements such as light propagation need to be investigated for parameters such as absorbance, transmittance and scattering. In this study, the backscattered light is studied and modelled using MATLAB based on Brillouin and Rayleigh scattering. The scattering effects on the output power and Stokes power are clearly seen where both powers reduce with the increase of fibre length. The Rayleigh power in terms of Coherent Rayleigh Noise is studied where broader source linewidth, higher spatial resolution and lower group velocity produce less noise. The less fluctuation due to noise can be attributed to the less temporal and spatial fluctuations of the optical pump power or pump current. The output from this research can benefit experimental studies to design fibre optic sensors in future.