Influence of atmospheric turbulence on coherent source in a horizontal long-distance laser link

2020 ◽  
Vol 122 ◽  
pp. 105877
Author(s):  
Qiang Wang ◽  
Siyuan Yu ◽  
Yanping Zhou ◽  
Liying Tan ◽  
Jing Ma
Author(s):  
Mingyang Yang ◽  
Xuewu Fan ◽  
Hui Zhao ◽  
Chuang Li ◽  
Meng Xiang

Author(s):  
Arturo Rodriguez ◽  
Carlos R. Cuellar ◽  
Luis F. Rodriguez ◽  
Armando Garcia ◽  
V. S. Rao Gudimetla ◽  
...  

Abstract The Large Eddy Simulations (LES) modeling of turbulence effects is computationally expensive even when not all scales are resolved, especially in the presence of deep turbulence effects in the atmosphere. Machine learning techniques provide a novel way to propagate the effects from inner- to outer-scale in atmospheric turbulence spectrum and to accelerate its characterization on long-distance laser propagation. We simulated the turbulent flow of atmospheric air in an idealized box with a temperature difference between the lower and upper surfaces of about 27 degrees Celsius with the LES method. The volume was voxelized, and several quantities, such as the velocity, temperature, and the pressure were obtained at regularly spaced grid points. These values were binned and converted into symbols that were concatenated along the length of the box to create a ‘text’ that was used to train a long short-term memory (LSTM) neural network and propose a way to use a naive Bayes model. LSTMs are used in speech recognition, and handwriting recognition tasks and naïve Bayes is used extensively in text categorization. The trained LSTM and the naïve Bayes models were used to generate instances of turbulent-like flows. Errors are quantified, and portrait as a difference that enables our studies to track error quantities passed through stochastic generative machine learning models — considering that our LES studies have a high state of the art high-fidelity approximation solutions of the Navier-Stokes. In the present work, LES solutions are imitated and compare against generative machine learning models.


2018 ◽  
Vol 15 (8) ◽  
pp. 085201 ◽  
Author(s):  
Chun-Ling Luo ◽  
Peng Lei ◽  
Zong-Lin Li ◽  
Jin-Quan Qi ◽  
Xiao-Xin Jia ◽  
...  

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1778
Author(s):  
Qian Ma ◽  
Hengkai Zhao

A partial receiving scheme based on limited angular aperture multi-beam receiving and demultiplexing can solve the difficulty caused by the divergence of the vortex beam in the conventional whole beam receiving scheme and realize the long-distance transmission of the vortex wave. The propagation of the radio vortex beam in atmospheric turbulence is of significant importance in theoretical study and practical applications. In this paper, the influence of atmospheric turbulence on the performance of a radio vortex (RV) communication system based on a partial angular aperture receiving (PAAR) scheme under the horizontal non-Kolmogorov channel model is studied. The spiral spectrum of the PAAR scheme and the channel capacity of the RV communication system using the PAAR scheme are derived. Simulation results demonstrate that the selected transmission frequency range has a great influence on the RV communication system based on the PAAR scheme, and the choice of the orbital angular momentum (OAM) mode number L has an influence on the propagation distance. The capacity of RV communication systems based on the PAAR scheme increases with the increase of the transmission frequency in the selected transmission frequency range of 10 GHz–60 GHz. When the number of orbital angular momentum (OAM) modes L is small, we can improve the signal-to-noise ratio (SNR) to obtain a larger capacity of the RV communication system based on the PAAR scheme over a longer propagation distance.


1955 ◽  
Vol 33 (6) ◽  
pp. 316-346 ◽  
Author(s):  
F. H. Northover

In this part the general solution developed in Part I is applied to the case in which the refractivity profile contains sharp layers (i.e. local regions where μ and dμ/dh change very rapidly compared with their rate of variation in a "standard" type atmosphere). It is found that such layers, when well developed, can cause distant fields of the order of magnitude of those which have been observed, but present experimental evidence seems to indicate that scattering from atmospheric turbulence is usually the important factor. An attempt is made to work out a physical interpretation of the field-formation below the elevated layer.


1955 ◽  
Vol 33 (5) ◽  
pp. 241-256 ◽  
Author(s):  
F. H. Northover

Reliable propagation of V.H.F. waves and microwaves from high power transmitters to distances of several hundred miles beyond optical range has been demonstrated by an ever increasing number of experiments during the last ten years. The fields which have been observed have consistently been many times greater than the field strengths predicted by the "effective radius" theory. The present paper will be published in two parts. In Part I the theory that the phenomenon can be explained solely in terms of "partial internal reflection" from elementary layers of a dielectric distribution where the rate of decrease of (μ – 1) with height is everywhere continuous and of the same order of magnitude as in a "standard" atmosphere is carefully examined and found to be untenable. In Part II, the case where the distribution contains "sharp layers" (i.e., local regions where (μ – 1) changes relatively rapidly with height) is examined and it is found that these could cause the phenomenon. However, in view of the other characteristics of the observed field, it is concluded that the effect in question is probably more usually due to scattering of the electromagnetic waves from atmospheric turbulence.


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