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INTRODUCTION: Rayleigh scatt ering (named after the British physicist Lord Rayleigh) is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light, which may be individual atoms or molecules. It can occur when light travels through transparent solids and liqui ds, but is most prominent ly seen in gases. Rayleigh scattering is a fu nction of the electricpolarizability of the particles. Rayleigh scattering of sunlight in the atmosphere causes diffuse, which is the reason for the blue color of the sky and the yellow tone of the sun itself scattering by  particles s imilar to or larg er than the wavelength of light is typically tr eated by the Mie theor y or the discrete dipole . In fiber optics, the mode field diameter (MFD) is an expression of distribut ion of the irradiance, i.e., the optical power per unit a rea, acr oss th e end face of a single-mode fiber. For a Gaussian intensity (i.e. power density, W/m 2 ) distribut ion in a single-mode optical fib er, t he mode field diameter is that at which the electric and magnetic field strengths are reduced to 1/e2 of their maximum values, i.e., the diameter at which power density is reduced to 1/e 2 of the maximum power density, because the power density is proportional to the square of the field strength. BASIC CONCEPT: RAY LIGHT SCATTERING IN FIBER: Rayleigh scattering is an important component of the scattering of optical signals in optical fibers. Silica fibers are disordered materials, thus their density varies, on a microscopic scale. The density fluctuations gives rise to energy loss due to the scattered light, with the following coefficient: Where n is the refraction index,  p is the photo elastic coefficient of the glass, k is Boltzmann constant, and is the isothermal compressibility. T  f is a f ictive temperature, representing the temperature at which the density fluctuations are "frozen" in the material.

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8/7/2019 focreylight

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MATLAB CODE FOR LOSS DUE TO RAYLIGHT SCATTERING:

clc;

clear all;alpha0 = 1.7;

lamda0 = 0.85;x = [700:1:1700];

Ralpha = alpha0*((lamda0/0.7)^4);

for i = x(1,2):x(1,1001)i = i/1000;Ralpha = [Ralpha,alpha0*((lamda0/i)^4)];

i = i*1000;end

x = x/1000;

 plot(x,Ralpha,'r');xlabel(' wavelength (micro meter) -------->');ylabel(' Rayleigh scattering (dB/km) --------->');

grid;

lamda = input('enter the wavelength in micrometer at which loss is to be calculated = ');Ralpha = alpha0*((lamda0/lamda)^4);disp('rayleigh scattering at given wavelength(dB/km)is =');

disp(Ralpha);

SIMULATION RESULTS:

enter the wavelength in micrometer at which loss is to be calculated = 1.5

rayleigh scattering at given wavelength(dB/km)is =

0.1753

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MATLAB CODE FOR MODEFILED DAIMETER:

clc;

clear all;d=input('diameter of core in micrometer=');n1=input('index of core=');n2=input('index of cladding=');

%NA=((n1^2)-(n2^2))^(1/2);

 NA = 0.13;d=d*1000;% convert diameter micrometer to nanometer 

Lamda = input('operating Wavelength at which number of modes to be calculated in nanometer=');%800to 1600 nanometer 

Vnumber = pi*d*NA/Lamda;MFD = 2*(d/2)*(0.65+(1.619/(Vnumber^(3/2)))+2.879/(Vnumber^6));

MFD = round(MFD);

MFD = MFD/1000;%convert MFD to micrometer disp('mode field diameter in micrometer = ');

disp(MFD);

SIMULATION RESULTS:

diameter of core in micrometer=1

index of core=1index of cladding=1.2

operating Wavelength at which number of modes to be calculated in nanometer=1.5mode field diameter in micrometer =

0.6500

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CONCLUSION:

From the results of the simulations one can conclude that if one knows the wavelength then

through it we can find loss due to ray light scattering in dB/km in fiber. This value is same as theoretical

value. If we know the diameter of core in micrometer, index of core, index of cladding then we get the

value of operating Wavelength at which number of modes to be calculated in nanometer.

ACKNOWLEDGEMENT:

We would like to thank Prof. Dhaval Pujara, for all the necessary guidance and information for 

the simulation code. His suggestion on how to improve the contents and design has made a definite

impact on this report and finally we would like to thank our family and friends for their coordination.