Common omissions and misconceptions of wave propagation in turbulence: discussion

Charnotskii, Mikhail

doi:10.1364/josaa.29.000711

Cited by 54 publications

(27 citation statements)

References 15 publications

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“…There are situations when there is an optimal distance between receivers that minimizes the probability of fade. We believe that this is related to the essential presence of the negative covariance of irradiance imposed by the energy conservation [16]. Overall impression is that there is no gain in making separation larger than 5 C r .…”

Section: Scintillations After Turbulent Phase Screenmentioning

confidence: 91%

Internal anisotropy of the turbulent scintillations

Charnotskii

2014

SPIE Proceedings

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We introduce a new concept of the Internal Anisotropy (IA) for the homogeneous and isotropic random fields. IA reflects the hidden structures that can exist in the samples of the random field, and are not revealed by the simplest, single and two-point statistical moments. There is presently no established theory of the IA, and no quantitative metrics of IA are available. It is understood, however, that IA cannot be present in any stationary isotropic Gaussian random field, or any single-point transformations of it. We illustrate the IA concept on a simple toy model of two-dimensional random field, and show that IA can affect the third and higher-order multipoint statistical moments. We generate samples of the random irradiance distributions for the plane wave passed through a phase screen with the quasiKolmogorov statistics. Visual evaluation suggests the presence of the IA in the irradiance samples. The statistical analysis reveals that the three-point third moment of irradiance exhibit the features consistent with the IA, especially in the focusing conditions. Conditional probabilities of the irradiance gradient components also proved to be sensitive to the IA. We discuss the role of the IA for optimal placement of the multiple receivers of the FSO system using the spatial diversity for fade mitigation.

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Section: Scintillations After Turbulent Phase Screenmentioning

confidence: 91%

Internal anisotropy of the turbulent scintillations

Charnotskii

2014

SPIE Proceedings

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“…Considering the uncertainty in comparison of the propagation results for different spectral models recently discussed in 13,14 , this seems a reasonable choice. While by no means universal, this normalization circumvents the dependence of results on the choice of the unit of length discussed in 13,14 . However, a definition of the coherence radius that is different from Eq.…”

Section: Monte-carlo Model For the Deep Turbulence Phasementioning

confidence: 99%

Modeling of the turbulent phase in strong scintillation conditions

Charnotskii

2014

SPIE Proceedings

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Monte-Carlo models of the turbulent phase are widely used in the studies of the optical propagation through turbulence atmosphere. However all algorithms, that are currently in use, generate continuous smooth phase samples. Meanwhile, it is well-known that under strong scintillation conditions turbulent phase has singularities, and phase is discontinuous across the branch cuts connecting the singularities. Markov approximation for wave propagation through random inhomogeneous media 1, 2 predicts that under the strong scintillation conditions optical field asymptotically has normal distribution 3 . We propose to generate the phase samples under strong scintillation conditions by first producing a complex normal random field with a given coherence function, and then recovering the random phase as the argument of this field. This approach allows generation of the two-dimensional discontinuous random phase samples that include phase singularities. Phase simulation algorithm is based on the Sparse Spectrum concept that was introduced in our earlier works, and can be modified to fit any desired shape of the turbulence spectrum. We verify the accuracy of the phase samples statistics by comparison with the theoretical results presented in the companion paper.

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“…Consequently, a modeling compromise was adopted based on Fried's quadratic correction to the long-exposure (LE) MTF. This approach was subsequently critiqued by Charnotskii [25][26][27][28] who argued its quadratic term would produce inaccurate results at high frequency.…”

Section: Introductionmentioning

confidence: 99%

Extended high-angular-frequency analysis of turbulence effects on short-exposure imaging

Tofsted

2014

Opt. Eng

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Abstract. An improved analysis of optical turbulence effects on short-exposure passive (SE) imaging is described, resulting in a new analytic expression for the SE modulation transfer function (MTF). This analysis expands on a 2011 study that examined characteristics of a tilt-phase component discovered in the standard theory of SE turbulence effects characterization. The analysis introduces an improved integration technique and a reformulated phase structure function, facilitating computation of a 38,007 element database of MTF results at low-to high-angular frequencies covering a wide range of diffraction and turbulence conditions. Analysis of this database is described, yielding a new analytic SE MTF, accurate to a root-mean-square error of 0.000218 versus the database. Comparisons show that the new expression is well correlated to an alternative computationally intensive method, and it is a factor 29 to 64 improvement over prior analytic expressions. Limits of applicability of the approach for incoherent imaging are also discussed. The low-computational cost of the new method is suitable for systems performance modeling of turbulence impacts, including path-varying turbulence scenarios. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Common omissions and misconceptions of wave propagation in turbulence: discussion

Cited by 54 publications

References 15 publications

Internal anisotropy of the turbulent scintillations

Internal anisotropy of the turbulent scintillations

Modeling of the turbulent phase in strong scintillation conditions

Extended high-angular-frequency analysis of turbulence effects on short-exposure imaging

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