Scattering losses in optical fiber

Attenuation is the main loss mechanism in an optical fiber. Absorption and scattering of signals results in attenuation. There are two types of scattering losses. They are linear scattering and nonlinear scattering. In linear scattering, attenuation occurs when optical power is transferred from one mode to another keeping frequency unaltered. There are two categories in linear scattering. They are Rayleigh scattering and Mie scattering. Rayleigh scattering is the main loss mechanism in the visible range. It is proportional to the fourth power of the operating wavelength. Rayleigh scattering loss can be minimized by choosing longest possible operating wavelength. If the size of the defect is greater than one-tenth of the wavelength of light, the scattering mechanism is called Mie scattering. Non linear scattering occurs when frequency is changed during optical power transfer. The two types of nonlinear scattering are stimulated Brillouin scattering and stimulate Raman scattering. Stimulated Brillouin scattering is a cause of concern in long distance systems, in wavelength division multiplexing (WDM) systems and remote pumping of an erbium doped fiber amplifier (EDFA) through a separate optical fiber. Stimulated Raman scattering creates problems in wavelength division multiplexing (WDM) systems.