&lt;title&gt;Fourier-series-based phase and amplitude optical field screen generator for weak atmospheric turbulence&lt;/title&gt;

Louthain, James A.; Welsh, Byron M.

doi:10.1117/12.323950

Cited by 6 publications

(7 citation statements)

References 5 publications

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“…The process to be simulated is expanded over a set of some basic functions (Fourier series : Sedmak 2004;Louthain & Welsh 1998, Zernike polynomials: Roddier 1990, Karhunen-Loeve functions: Cannon 1995Orlov et al 1998, etc. ), and the expansion coefficients are sought in such a way as to allow one to reproduce the given statistics in simulated samples.…”

Section: Introductionmentioning

confidence: 99%

Simulating the phase fluctuations produced by many stars in the weak atmospheric turbulence limit

Voitsekhovich

Kouznetsov

Orlov

2005

A&A

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We propose a method allowing for a simulation of cross-correlated turbulence-induced phase fluctuations produced by many stars is proposed. It turns out that for weak-turbulence conditions which are important for many applications, it is possible to suggest a relatively simple and fast simulation procedure. Both the variation of C 2 n along a propagation path and an effect of finite outer scale of the turbulence are considered. The validity of the simulation is verified by comparing theoretical and simulated results, and it is shown that there is good agreement takes place even for big separations between the observation points. Adaptive optics, guide stars, speckle interferometry, long-base interferometry, imaging through the turbulence, as well as simulations of the image distortions of extended objects are among the possible applications of this method.

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Section: Introductionmentioning

confidence: 99%

Simulating the phase fluctuations produced by many stars in the weak atmospheric turbulence limit

Voitsekhovich

Kouznetsov

Orlov

2005

A&A

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“…The low spatial frequencies (e.g., tilt) contain a large fraction of the power for atmospheric-turbulence-induced-wavefront perturbations. A modal-based approach allows for much better low frequency representation [48,66,83].…”

Section: Layered Atmosphere Modelmentioning

confidence: 99%

“…(Many times the centroid was located in a low intensity location on the aperture) In addition, new tracking and pointing algorithms could be developed for multiple-transmitter systems, since the separation required to average out the scintillation is smaller than the tilt isoplanatic angle. Scintillation does adversely affect centroid determination in a centroid-tracking system [48].…”

Section: Tracking Systemsmentioning

confidence: 99%

“…The turbulence effects explored subsequently in simulated scenarios were generated using 10 Fourier-series-based random phase screens with the correct statistics placed along the path [48,83]. The layered analytic spherical coherence diameter r 0sp , spherical Rytov number R sp , and isoplanatatic angle θ 0 matched within 1% of the full path continuous atmospheric turbulence parameters.…”

Section: Modeling the Turbulencementioning

confidence: 99%

“…FS-based phase screens were used, since it allows for better low spatial frequency representation than other techniques [45,48,66,67,83]. This modal phase screen is defined in terms of the spatial frequencies of the refractive-index PSD and need only be evaluated at the grid points of interest.…”

Section: Simulation Set-upmentioning

confidence: 99%

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Integrated approach to airborne laser communication

Louthain¹

2008

SPIE Proceedings

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Lasers offer tremendous advantages over RF communication systems in terms of bandwidth and security due to their ultra-high frequency and narrow spatial beamwidth. Unfortunately, atmospheric turbulence significantly increases the received power variation and bit error rate (BER) in free-space optical communication (FSOC) systems. Further, airborne optical communication systems require special considerations in size, complexity, power, and weight.If two or more laser beams are sufficiently separated so that their turbulence effects are uncorrelated (i.e. anisoplanatic), they can effectively "average out" turbulence effects. This requisite separation distance is derived for multiple geometries, turbulence conditions, and optical properties. In most cases and geometries, the angles ordered from largest to smallest are: phase uncorrelated angle (equivalent to the tilt uncorrelated angle and phase anisoplanatic angle), tilt isoplanatic angle, phase isoplanatic angle, scintillation uncorrelated angle (or scintillation anisoplanatic angle), and scintillation isoplanatic angle (θ ψ ind > θ T A > θ 0 > θ χ ind > θ χ 0 ). Conventional adaptive optics (AO) systems only correct for phase and cannot correct for strong scintillation, while multiple-transmitter systems use several transmission paths to "average out" effects of the strong scintillation by incoherently summing up the beams in the receiver.Since all three airborne geometries (air-to-air, air-to-ground, and ground-toair) are studied, a comparison of multiple-beam airborne laser communication system performance is presented for the first time. Wave optics simulations show that a combination of transmitter diversity, receiver and transmitter trackers, and adaptive thresholding can significantly reduce BER in an air-to-air FSOC system by over 10,000 times. As demonstrated in this work, two transmitters alone separated by only 31 cm (100 km path length, 1.55 µm wavelength, 4 km in altitude) provide a significant iv BER improvement over one transmitter, especially for the strong turbulence regime where the required SNR for a fixed BER is reduced by 9 dB. Including the tracking and adaptive thresholding techniques, resulted in a 13 dB overall improvement.Two beams also reduce the fade length, suggesting even greater improvement can be obtained when interleaving and forward error correction coding is implemented. Major Schmidt also knew when to hand me water and how to keep me on the road, since he had just finished his marathon.

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Calculation of minimum-variance estimators for Hartmann sensing using random wave vector simulations

Voitsekhovich

Bará

Mayor

2001

J. Opt. A: Pure Appl. Opt.

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<title>Fourier-series-based phase and amplitude optical field screen generator for weak atmospheric turbulence</title>

Cited by 6 publications

References 5 publications

Simulating the phase fluctuations produced by many stars in the weak atmospheric turbulence limit

Simulating the phase fluctuations produced by many stars in the weak atmospheric turbulence limit

Integrated approach to airborne laser communication

Calculation of minimum-variance estimators for Hartmann sensing using random wave vector simulations

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