Effect of attenuation in optical fiber

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Effect of attenuation in optical fiber

A minimum optical input is required by a receiver in an optical system for it to be able to operate with a specified probability error. Attenuation in an optical medium, reduces the power available at the output and consequently degrades the probability error. Most systems are known to have a probability error of up to 1 x 10-9. The operating span of a communication system is limited by attenuation effects in the system as it limits the power that can reach the receiver.Effect of attenuation in optical fiber

The types of attenuation include: absorption loss which is as a result of the fibre itself or impurities within it, scattering loss which is an intrinsic mechanism loss that arises due to the association between the photons with the glass and bending loss that arises due to stress on the fibre.

In light scattering, the transmission of light through the optical fibre core relies on the light wave’s total internal reflection. Diffuse reflection can occur if there exist rough surfaces, even at the molecular level. This is also referred to as light scattering, which depends on the wavelength of the scattered light resulting to a limit in spatial visibility. Depending on the incident light wave’s frequency and spatial scale, the dimensions of the scattering centers will have the same spatial scale. Therefore, attenuation arises from random scattering of light on the interfaces and internal surfaces.

When attenuation occurs the strength of signal gradually falls along the transmission medium, the longer the distance travelled by the signal in the transmission medium the weaker the signal becomes. Generally in a guided medium, the strength of the signal can be mathematically expressed as….Effect of attenuation in optical fiber……

Where  a function of frequency, and the attenuation is expressed as:


For the case of unguided media, attenuation becomes a more complex function of the distance and the composition of the atmosphere. This is because for example signals passing through the atmosphere usually pass through different layers making the analysis complex. Attenuation has the impact of creating a demand on the signal