Phase diffuser at the transmitter for lasercom link: effect of partially coherent beam on the bit-error rate

Korotkova, Olga; Andrews, Larry C.; Phillips, Ronald L.

doi:10.1117/12.473178

Cited by 11 publications

(5 citation statements)

References 15 publications

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“…The quantity x in Eq. ͑40͒ is the normalized large-scale cutoff frequency determined by the asymptotic behavior of ln x 2 in weak turbulence and saturation regime 36,38 :…”

Section: ͑40͒mentioning

confidence: 99%

Model for a partially coherent Gaussian beam in atmospheric turbulence with application in Lasercom

Korotkova

2004

Opt. Eng

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211

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Analytic expressions for the mutual coherence function (MCF) and the scintillation index of a partially coherent lowest order Gaussian beam wave propagating through the atmosphere (based on Kolmogorov spectrum model) are developed for the pupil plane of a receiving system. Partial coherence of the beam is modeled as a thin (complex) phase screen with Gaussian spectrum (Rytov theory and ABCD ray matrices are applied). The relation between the second-and fourth-order statistics for a beam with any degree of coherence in the atmosphere is introduced with the help of ''effective'' beam parameters, deduced from the free-space MCF. In particular, the scintillation (in weak and strong atmospheric conditions), based on these parameters, is studied as a function of the diffuser's strength and that of the atmosphere. The model is applied for the calculation of the SNR and bit error rates (OOK modulation) of the communication link with diffuser at the transmitter and slow detection system. The improvement of bit error rates is observed in weak and strong atmospheric turbulence. In the weak regime, the optimal diffuser can be found. © 2004 Society of Photo-Optical Instrumentation Engineers.

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“…The quantity x in Eq. ͑40͒ is the normalized large-scale cutoff frequency determined by the asymptotic behavior of ln x 2 in weak turbulence and saturation regime 36,38 :…”

Section: ͑40͒mentioning

confidence: 99%

Model for a partially coherent Gaussian beam in atmospheric turbulence with application in Lasercom

Korotkova

2004

Opt. Eng

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211

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“…The spatial diffuser placed over the laser exit is modeled as a thin complex phase screen with a Gaussian spectrum model [5][6][7] ( ) where κ (m -1 ) is the atmospheric wave number, l c (m) is the lateral correlation radius of the Gaussian phase screen. In model (2.2), <n 1 2 > is the fluctuation in the index of refraction induced by the screen.…”

Section: Basic Modelmentioning

confidence: 99%

“…Although simply physically realizable Free-Space Laser Communication and Active Laser Illumination III, edited by David G. Voelz, Jennifer C. Ricklin (usually with the help of a commercially sold diffuser placed over the laser exit) the new approach requires the development of a theoretical model for partially coherent beams propagating in atmospheric turbulence that could be useful for the FSO system design. Usually in literature existing on this account [10][11][12][13][14][15][16][17][18] one can find the analytic results only for two limiting cases of fast and slow detection and only for one of the atmospheric conditions: weak fluctuations or saturation regime. A model valid in all atmospheric fluctuations (weak-moderate-strong) was suggested by the authors for the particular case of a slow detector [5][6][7] where it was demonstrated that the application of the diffuser can significantly improve the FSO system performance. The purpose of this paper is to extend previous results to the case of arbitrary detection speed.…”

Section: Introductionmentioning

confidence: 99%

The effect of partially coherent quasi-monochromatic Gaussian beam on the probability of fade

2004

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The effect of a (spatially) partially coherent quasi-monochromatic lowest order Gaussian-beam on the direct detection system is studied in weak and strong atmospheric turbulence. The analytic expression for the scintillation index has been developed and analyzed as a function of the spatial correlation distance c l and the correlation time τ s , associated with the source, as well as the strength of turbulence and the integration time τ d of the detector. The probability of fade is also discussed as a function of relative detector speed τ d / τ s. including limiting cases of slow (τ d >>τ s ) and fast (τ d <<τ s ) detector.

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“…Although conceptually this idea seems to be similar to our proposal, the motivation in [37,38] is to reduce the scintillation at the entrance pupil of the coupler. As it is clear from our analysis, phase disturbances play the dominant role for the PIF fluctuations.…”

Section: Adaptive Optics and Fadingmentioning

confidence: 72%

“…Papers [37,38] considered the mitigation of the PIF scintillation by using the partially-coherent sources, or equivalently a diffuser place at the transmitter plane L z = in our notations. Although conceptually this idea seems to be similar to our proposal, the motivation in [37,38] is to reduce the scintillation at the entrance pupil of the coupler.…”

Section: Adaptive Optics and Fadingmentioning

confidence: 99%

Coupling turbulence-distorted wave front to fiber: wave propagation theory perspective

Charnotskii

2010

Free-Space Laser Communications X

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We use the results of the theory of wave propagation in turbulence to analyze the effects of the atmospheric turbulence on the Free-Space Optical Communication systems under weak and strong scintillation conditions. We found that for the traditional fiber coupling arrangement statistics of the Power-in-Fiber (PIF) is sensitive to the phase fluctuation at the collecting aperture, rather than amplitude fluctuation (scintillation). Larger receiving aperture produces stronger PIF fluctuation. Similar to the scintillation of the sharp focused beams second-order scattering dominates PIF fluctuation for the weak and strong scintillation conditions. This should have serious effect on the probability distribution of the PIF.A new coupling arrangement is suggested that alleviates the destructive effect of the phase fluctuation, and allows the use of large receiving apertures. The trade-off is the decreased coupling efficiency. For our new coupling scheme the PIF fluctuation is determined by the power flux fluctuation through the collecting aperture. This allows taking advantage of the scintillation averaging effect to suppress the fading. We review the results of the rigorous Markov-approximationbased theory of the scintillation averaging that is valid both for a weak and strong scintillation conditions. This technique reveals several distinct regimes of the power flux fluctuation including the situation where fluctuation is relatively small, but is not described by the perturbation (Rytov's) theory. We also show how the energy conservation principle inherent to the wave propagation in the clear air turbulence provides an accelerated rate of the scintillation averaging compare to the typical averaging estimates.

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Phase diffuser at the transmitter for lasercom link: effect of partially coherent beam on the bit-error rate

Cited by 11 publications

References 15 publications

Model for a partially coherent Gaussian beam in atmospheric turbulence with application in Lasercom

Model for a partially coherent Gaussian beam in atmospheric turbulence with application in Lasercom

The effect of partially coherent quasi-monochromatic Gaussian beam on the probability of fade

Coupling turbulence-distorted wave front to fiber: wave propagation theory perspective

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