Characterizing the propagation path in moderate to strong optical turbulence

Vetelino, Frida Strömqvist; Clare, Bradley A.; Corbett, Kerry A.; Young, Cynthia; Grant, Kevin; Andrews, Larry C.

doi:10.1364/ao.45.003534

Cited by 31 publications

(14 citation statements)

References 19 publications

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“…Optical measurements, in combination with a scintillation theory developed by Andrews et al 17,25 were used to infer the refractive index structure parameter C n 2 , the inner scale of turbulence l 0 , and the outer scale of turbulence L 0 , along the propagation path. 26 The theoretical expressions for the scintillation index, at a fixed range and wavelength, depend on four parameters: C n 2 , l 0 , L 0 , and D. By specifying three different collecting aperture sizes, and measuring the corresponding scintillation index experimentally, a minimization problem for the atmospheric parameters was created. It was solved numerically with the downhill simplex method, 26,27 which is a multidimensional minimization algorithm that requires only function evaluations, not derivatives.…”

Section: A Experimental Datamentioning

confidence: 99%

“…26 The theoretical expressions for the scintillation index, at a fixed range and wavelength, depend on four parameters: C n 2 , l 0 , L 0 , and D. By specifying three different collecting aperture sizes, and measuring the corresponding scintillation index experimentally, a minimization problem for the atmospheric parameters was created. It was solved numerically with the downhill simplex method, 26,27 which is a multidimensional minimization algorithm that requires only function evaluations, not derivatives. The experimental scintillation index was measured for the same 5 min of data used to calculate the PDF, at each receiving aperture (1, 5, and 13 mm diameter).…”

Section: A Experimental Datamentioning

confidence: 99%

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Aperture averaging effects on the probability density of irradiance fluctuations in moderate-to-strong turbulence

et al. 2007

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The lognormal (LN) and gamma-gamma (GG) distributions are compared to simulated and experimental data of the irradiance fluctuations of a Gaussian beam wave propagating through the atmosphere along a horizontal path, near the ground, in the moderate-to-strong turbulence regime. Irradiance data were collected simultaneously at three receiving apertures of different sizes. Atmospheric parameters were inferred from the measurements and scintillation theory and were used to develop the parameters for the theoretical probability density functions. Numerical simulations were produced with the same C n 2 value as the experimental data. Aperture-averaging effects were investigated by comparing the irradiance distributions for the three apertures at two different values of the structure parameter C n 2 , and, hence, different values of the coherence radius 0 . For the moderate-to-strong fluctuation regime, the GG distribution provides a good fit to the irradiance fluctuations collected by finite-sized apertures that are significantly smaller than 0 . For apertures larger than or equal to 0 , the irradiance fluctuations appear to be LN distributed.

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Section: A Experimental Datamentioning

confidence: 99%

Section: A Experimental Datamentioning

confidence: 99%

Aperture averaging effects on the probability density of irradiance fluctuations in moderate-to-strong turbulence

et al. 2007

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“…Unlike previous work [4,17], an optical intensity-modulated sinusoid is transmitted through the channel to measure the loss and fading, h(t) in Eq. (2).…”

Section: A Measurement Proceduresmentioning

confidence: 99%

Channel Measurement and Markov Modeling of an Urban Free-Space Optical Link

Mostafa

Hranilovic

2012

J. Opt. Commun. Netw.

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Free-space optical (FSO) communication links provide high data rates; however, their reliability is heavily dependent on weather conditions. This paper presents our experimental urban 1.87 km FSO link based on a customized commercial system and develops a library of channel measurements in clear and light rain weather conditions. A channel model for the link is proposed and experimentally quantified. Channel measurements are obtained by modulating a 60 mW laser source. At the receiver, a 2 GSa/s data converter is used and 16 fast-Fourier transform cores are implemented in the hardware to improve noise immunity. The resulting signal-to-noise ratio of the channel samples is around 40 dB under clear weather conditions. Fittings with log-normal, gamma-gamma, and Erlang distributions are presented, and the scintillation index and coherence time are measured. A computationally efficient finite-state Markov chain is derived for the channel to model both the distribution and the autocorrelation of the fading and is verified by the measurements. The Markov models and channel measurements in a variety of atmospheric conditions are available for download to permit easy verification of communication algorithms on this urban FSO channel.

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“…A number of recent papers [1][2][3][4][5][6][7][8][9][10][11][12][13][14] discussed the issues related to the performance of the Free-Space Optical Communication Systems (FSO) in the turbulent atmosphere. In the literature the emphasis is made on the mitigating the signal fading due to the turbulence-induced fluctuation by the aperture averaging of the scintillations or spatial diversity.…”

Section: Introductionmentioning

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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Characterizing the propagation path in moderate to strong optical turbulence

Cited by 31 publications

References 19 publications

Aperture averaging effects on the probability density of irradiance fluctuations in moderate-to-strong turbulence

Aperture averaging effects on the probability density of irradiance fluctuations in moderate-to-strong turbulence

Channel Measurement and Markov Modeling of an Urban Free-Space Optical Link

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

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