From Free-Space Optics: Propagation and Communication
4.4. Meteorological Disturbances
4.4.1. Mie Scattering Attenuation
184.108.40.206. Theoretical Aspect
The phenomenon of scattering occurs when t he size of particles is of the same order of magnitude as the wavelength of the transmitted wave. In optics this is mainly due to mist and fog. Attenuation is a function both of frequency and of visibility related to the particle size distribution. This phenomenon constitutes the most restrictive factor to the deployment of Free-Space Optical systems over long distances.
Attenuation can reach 300 dB per km whereas rain attenuation in millimeter waves is only about 10 dB per km. The scattering coefficient ?n is given by the following equation:
? n( ?), in km -1, is the scattering coefficient of the aerosol,
?, in ?m, is the wavelength,
dN( r)/ dr, in cm -4, is the particle size distribution per unit of volume,
n' is the real part of the refractive index n of the considered aerosol,
r, in cm, is the radius of the particles,
Q d( 2 ?r/ ?, n') is the scattering cross section for a given type of aerosol.
Mie theory allows the expression of the scattering coefficient Q d due to the aerosol. This is calculated on the assumption that the particles are spherical and sufficiently distant from each other so that the field of scattering by a particle and of interaction with another one can...
Products & Services
Topics of Interest
4.5. Free-Space Optical Links In this chapter, some of the aspects of propagation to be considered at the point of installation of Free-Space Optical (FSO) links were presented (for example,...
OVERVIEW Aerosol light scattering plays a major role in the design of aerosol measurement systems (discussed in the next chapter) and radiation transfer through the atmosphere. There are also...
2.1. INTRODUCTION Both the Rayleigh and the Mie theories, which are based on the Maxwell equations, model the scattering of a plane monochromatic optical wave by a single particle. Even if the...
1.3 Scattering Cross Section As we have seen, the scattering of a particle in a potential is completely determined once we know the impact parameter and the energy of the particle; and, for a fixed...
The technique of laser diffraction relies on the fact that particles passing through a laser beam scatter light at an angle that is inversely proportional to their size (small particles scatter light...