Fiber attenuation

The factors that cause fiber attenuation include scattering loss, absorption loss, and microbending loss. The scattering loss is mainly caused by Rayleigh scattering, which is caused by the microscopic refractive index fluctuation caused by the irregular molecular structure of the glass. It is the inherent loss of the fiber and the minimum attenuation of the fiber. It is inversely proportional to λ4. At wavelengths less than 0.8 μm, the Rayleigh scattering loss rises rapidly, limiting the use of optical fibers. The intrinsic absorption loss of the fiber matrix material SiO2 and doped oxide molecules makes the attenuation of the fiber increase rapidly when the wavelength is greater than 1.7 microns. Therefore, the use wavelength of this kind of fiber is limited in the range of 0.8-1.7 microns. In this range, the attenuation is mainly the transition metal ions such as Fe + + and Cu + + and OH- contained in the quartz glass. due to absorption losses. With the improvement of the purification process, the impurity absorption loss has been substantially eliminated, thus reaching the limit of the Rayleigh scattering loss. The irregular micro-bending of the optical fiber causes mode coupling, resulting in micro-bending loss. Therefore, the micro-bending of the optical fiber should be avoided as much as possible during processing and use.