Fiber Scattering Loss

Scattering loss is the loss caused by the optical power coupling out or leaking out of the fiber core due to the micro-fluctuation of the atomic density in the fiber material components or the structural defects of the fiber waveguide.
Intrinsic scattering is the most important scattering in material scattering, and its loss power is linear with the power of the propagating mode. It is due to the inhomogeneity of material atoms or molecules and material structure. The microscopic inhomogeneity of the refractive index of the material causes the scattering of the transmitted light wave. This kind of scattering is inherent in the material and cannot be eliminated. It is the lowest limit of fiber loss, and Rayleigh scattering belongs to this category. The Rayleigh scattering loss is inversely proportional to the fourth power of the wavelength. When working at long wavelengths, the loss of the optical fiber can be greatly reduced.
Another type of intrinsic scattering is caused by uneven doping. In optical fiber manufacturing, in order to change the refractive index of glass, it is necessary to dope some kind of oxide. This kind of scattering will be caused when the concentration of oxide is uneven or fluctuates.
Nonlinear scattering includes stimulated Brillouin scattering and stimulated Raman scattering. Under the action of strong optical power density in the medium, phonons will be generated when the incident photons collide with the medium molecules inelastically. When the light is scattered by the propagating acoustic phonons, it is called Brillouin scattering; when the light is scattered by the molecular vibration Or when scattered by optical phonons, it is called Raman scattering. Both types of stimulated scattering have a threshold power that occurs only above this value. In common optical communication systems, the optical power input to the optical fiber is generally low, and nonlinear scattering usually does not occur.