A study of the potential advantages of light beams in weak and strong turbulent atmospheres to satisfy robust free space communication channels with longer link distances

Firstly, plane phase distribution sources and receivers with multi-values of topological charge were evaluated in this study. This evaluation was implemented in a computer environment. It is expected that our results will be beneficial to optical links incorporating the use of the Gaussian vortex, Elliptical Gaussian vortex, and Laguerre-Gaussian vortex beams. Computer modeling of the phase distributions of vortex beams was investigated by numerical simulation of propagation through free space. This work will help to know the phase distribution receiver by changing the numbers of the topological charge and to estimate those receivers' messages in the photodetector device. Secondly, a scintillation index (SI) formulation was carried out for the Gaussian beam on the propagation length in a turbulent atmosphere depending on the generalized beam formulation of the field. The scintillation methods were compared in order to determine the best method that describes the phenomenon. Three types of scintillation methods were examined: the Rytov, Huygens-Fresnel and Random Phase Screen. From our graphical outputs, it was observed that the Random Phase Screen exhibits an acceptable scintillation index value. Thirdly, the results indicate that the topological charge of the Laguerre-Gaussian beam has a greater effect than the degree of the polynomial on the SI values. Moreover, if the polynomial degree is fixed, the SI has lower values in cases of a topological charge increase. Therefore, for a good state of transmission, it is recommended that the degree of the polynomial be made equal to 1 and the topological charge numbers equal to 0, 1, 2, 3, 4, 5 and 6. Fourthly, the Gaussian, Elliptical, Laguerre and Bessel vortex beams were selected and measurements of the SI were computed for different values of the n and m parameters for their beams. Then, it was found that the Elliptical beam with topological charges equaling 7 and 3 was best. Fifthly, the Gaussian beam and Gaussian vortex beams were chosen and measurements of the scintillation index were computed for the different values of the parameters of the Gaussian vortex beams. Then, it was shown that the Gaussian vortex beams with the degree of the polynomial and the topological charge equaling values of n = 6, m = 3 and n = 5, m = 6 were better than the Gaussian beam. Despite the increasing propagation distance, the SI values of the Gaussian vortex beam remained between 0.04 and 0.14 with an increase in this propagation distance compared with the Gaussian beam, the value of whose scintillation index will increase with an increase in the propagation distance. Sixthly, receiver intensities for the Laguerre-Gaussian beam in free space are affected by changes in the polynomial parameters of the Laguerre beam. It becomes evident that when the degree of the polynomial and the topological charge parameters are the same, the receiver intensities of the Laguerre-Gaussian beam become more separate. Finally, we compute the Symbol Error Rate for the Gaussian vortex beam for 8 Mary against a structure constant, and it appears that the Symbol Error Rate increases with an increasing structure constant parameter. The prime idea of this study is that distribution sources and receivers are more beneficial to optical channels, and the Random Phase Screen method is an acceptable method for computing the scintillation; then the Gaussian vortex beam is better than the Gaussian beam, and we can change the values of the topology parameter and polynomial degree of the Laguerre-Gaussian beam or other beams, such as the Gaussian vortex beam, to decrease the value of the scintillation index. In the end, the symbol error rate is increased by increasing the structure constant of turbulence.