Rayleigh scattering is one of several optical backscattering phenomena. It is a light scattering caused by material inhomogeneities in an optical waveguide.
Caused by disordered, microcrystalline regions within the fused silica, Rayleigh scattering causes non-uniform deflection of light rays. It depends on the wavelength of the light and is less than 0.4 dB/km for silicon dioxide (SiO2) at a wavelength of 1300 nm. In Rayleigh scattering, the wavelength of the backscattered light is the same as that of the injected light. Rayleigh scattering is named after its discoverer Lord Rayleigh (1842 to 1919).