![]() ![]() This distortion is due to dispersion effect. The optical signal becomes increasingly distorted as it travels along a fiber. In such cases, even when the external forces are applied, the jacket will be deformed but the fiber will tend to stay relatively straight and safe, without causing more loss. Micro-bend losses can be minimized by extruding (squeezing out) a compressible jacket over the fiber. This lead to loss of light by leakage through the fiber. ![]() This micro bends in fiber appears due to non uniform pressures created during the cabling of the fiber or even during the manufacturing itself. Micro-bends losses are caused due to non-uniformities or micro bends inside the fiber as shown. Also note that this loss is negligible for small bends. This is called as macroscopic / macro bending losses. At these corners the light will not satisfy the condition for total internal reflection and hence it escapes out from the fiber. If the radius of the core is large compared to fiber diameter, it may cause large-curvature at the position where the fiber cable turns at the corner. Radiative loss occurs in fibers due to bending of finite radius of curvature in optical fibers. this type of scattering is called Raleigh scattering. As a result, if light is passed through the atoms in the fiber, a portion of light is scattered (elastic scattering). ![]() Since the glass is used in fabrication of fibers, the disordered structure of glass will make some variations in the refractive index inside the fiber. Scattering is also a wavelength dependent loss, which occurs inside the fibers. Usually absorption of light occurs due to imperfections of the atomic structure such as missing molecules, (OH -), hydroxyl ions, high density cluster of atoms etc., which absorbs light. Since attenuation plays a major role in determining the transmission distance, the following attenuation mechanisms are to be considered in designing an optical fiber. It is defined as the ratio of optical power output (P out) from a fiber of length ‘L’ to the power output (P in) The loss of optical power is measured in terms of decibels per km for attenuation losses. When light propagates through an optical fiber, a small percentage of light is lost through different mechanisms. ![]()
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