Module 4 : Signal Distortion on Optical Fibers - Attenuation
Lecture : Signal Distortion on Optical Fibers - Attenuation
MICRO-BENDING LOSSES
While commissioning the optical fiber is subjected to micro-bending as shown in Fig.
The analysis of micro-bends is a rather complex task. However, just for basic understanding of how the loss takes place due to micro-bending, we use following arguments.
In a fiber without micro-bends the light is guided by total internal reflection (ITR) at the core-cladding boundary. The rays which are guided inside the fiber has incident angle greater than the critical angle at the core-cladding interface. In the presence of micro-bends however, the direction of the local normal to the core-cladding interface deviates and therefore the rays may not have angle of incidence greater than the critical angle and consequently will be leaked out.
A part of the propagating optical energy therefore leaks out due to micro-bends.
Depending upon the roughness of the surface through which the fiber passes, the micro-bending loss varies.
Typically the micro-bends increase the fiber loss by 0.1-0.2 dB/Km.
