Gaussian beam scintillation index for slant path in weak turbulence: closed form expressions

2019 ◽  
Vol 51 (4) ◽  
Author(s):  
Asmaa M. Aly ◽  
Heba A. Fayed ◽  
Nour Eldin Ismail ◽  
Moustafa H. Aly
Author(s):  
Hussein Thary Khamees ◽  
Ali Abdul Wahhab Mohammed

The formula of the scintillation index fixated on bit error rate of Super Lorentz Gaussian beam in turbulent atmosphere is derivative by using the Huygens Fresnel Process to evaluate the average bit error rate. The scintillation index guides of a higher beam order engrossed Super Lorentz Gaussian beam flat and Cartesian coordinates are compared. The average signal-to-noise ratio is computed via the versus scintillation index and bit error rate by using the formula of log-normal dispersed intensity for the beam order and absorbed the Super Lorentz Gaussian beams (SLG) is propagated in the slant path, which display several factors such as source size, focal length and wavelength, for example, 0.8 and 1.55 μm. Absorbed beams are initiated to take significant compensations over higher order beams. According to the two desired wavelength distributions processed theoretically, the results of bit error rate estimation were started to the value of source size rises, the system is improved and scintillation index, bit error rate decreased, the quality of bit error rate was enhanced, and the elevation was decreased. Bit error rate quality estimation of full reference objective relay on the feedback by SLG22 beam has the better bit error rate.


Atmósfera ◽  
2015 ◽  
Vol 27 (4) ◽  
pp. 385-401
Author(s):  
SHIVAN M. AUGUSTINE ◽  
NAVEN CHETTY

In this work, we have modified an existing experimental setup to fully classify the thermal effects on a laser beam propagating in air. Improvements made to the setup include a new, more powerful laser, a precision designed turbulence delivery system, an imbedded pressure sensor, and a platform for height adjustability between the laser beam and the turbulence model. The setup was not only able to reproduce previous results exactly but also allowed new data for the turbulence strength C2n, the Rytov variance (scintillation) and the coherence diameter (Fried’s parameter) to be successfully measured. Analysis of the produced interferograms has been discussed using fast Fourier transforms. The results confirm, within the Kolmogorov regime, that phase and intensity fluctuations increase relative to temperature. The turbulent region exhibited very strong disturbances, in the range of 1.1 × 10–12 m–2/3 to 2.7 × 10–12 m–2/3. In spite of the strong turbulence strength, scintillation proved otherwise, since the condition for a weak turbulence environment was determined in the laboratory and a low scintillation index was to be expected. This is as a result of the relatively short propagation distances achieved in the laboratory. In the open atmosphere, path lengths extend over vast distances and in order for turbulent effects to be realized, the turbulence model must generate stronger turbulence. The model was, therefore, able to demonstrate its ability to fully quantify and determine the thermal turbulence effects on a propagating laser beam.


2018 ◽  
Vol 39 (2) ◽  
pp. 247-253 ◽  
Author(s):  
Rahul Kaushik ◽  
Vineet Khandelwal ◽  
R. C. Jain

AbstractWeak atmospheric turbulence condition in an optical wireless communication (OWC) is captured by log-normal distribution. The analytical evaluation of average bit error rate (BER) of an OWC system under weak turbulence is intractable as it involves the statistical averaging of Gaussian Q-function over log-normal distribution. In this paper, a simple closed form approximation for BER of OWC system under weak turbulence is given. Computation of BER for various modulation schemes is carried out using proposed expression. The results obtained using proposed expression compare favorably with those obtained using Gauss-Hermite quadrature approximation and Monte Carlo Simulations.


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