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Light Scattering Essay

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SCATTERING
Scattering takes place when obstacle dimension is smaller than wavelength of signal.Light scattering is a form of scattering in which light is the form of propagating energy which is scattered. Light scattering is deflection of a ray from a straight path i.e. Irregularities in the propagation medium, particles, or in the interface between two media. Deviations from the law of reflection due to irregularities on a surface are also usually considered to be a form of scattering. Scattering is defined as the dispersal of a beam of radiation into a range of directions as a result of physical interactions. When a particle intercepts an electromagnetic wave, part of the wave’s energy is removed by the particle and re-radiated into a solid
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Mie scattering is the main cause of attenuation at laser wavelength of interest for FSO communication at terrestrial altitude. Transmitted optical beams in free space are attenuated most by the fog and haze droplets mainly due to dominance of Mie scattering effect in the wavelength band of interest in FSO (0.5 μ m – 2 μ m). This makes fog and haze a keys contributor to optical power/irradiance attenuation. The attenuation levels are too high and obviously are not…show more content…
Scintillation may be the most noticeable one for FSO systems. Light traveling through scintillation will experience intensity fluctuations, even over relatively short propagation paths. The scintillation index, σi2 describes such intensity fluctuation as the normalized variance of the intensity fluctuations given by

here,
I = |E |2: is the signal irradiance (or intensity).

The strength of scintillation can be measured in terms of the variance of the beam amplitude or irradiance σi given by the following:

σi2 = 1.23Cn2 k 7/6L 11/6

Where Cn2 is the refractive index structure, k = 2π /λ is the wave number (an expression suggests that longer wavelengths experience a smaller variance), and l is the link range (m). Where the Eq. 26 is valid for the condition of weak turbulence mathematically
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