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1

Effect of circular aperture diffraction on propagation properties of cylindrical vector partially coherent Laguerre–Gaussian beams in turbulent atmosphere

Peng Z., Jia X.

Optica Applicata

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2018

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Vol. 48, nr 3

421--433

EN

On the basis of the extended Huygens–Fresnel integral formula, the analytical formulae for the cross-spectral density matrix of the arbitrary cylindrical vector partially coherent Laguerre–Gaussian beams diffracted by a circular aperture in turbulent atmosphere are derived. The average intensity, the degree of polarization, and the degree of coherence of the apertured cylindrical vector partially coherent beams propagating in turbulent atmosphere are investigated. The analyses indicate that both the beam diffraction effect by a circular aperture and the atmospheric turbulence have a great impact on the beam evolution, polarization and coherence properties of the apertured cylindrical vector partially coherent beams.

2

Characterization of sub-channel based Málaga atmospheric optical links with real β parameter

López-González F. J., Jurado-Navas A., Garrido-Balsells J. M., Castillo-Vázquez M., Puerta-Notario A.

Optica Applicata

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2017

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Vol. 47, nr 4

545--556

EN

A generalization of the Málaga atmospheric optical communications links treated as a finite number of generalized-K distributed sub-channels is analyzed in terms of outage probability and outage rate when its β parameter belongs to the set of real numbers. To the best of the author’s knowledge, this is the first time that β ∈ ℜ is considered. The new analytical expressions derived in this paper lead to a new physical and more realistic interpretation of atmospheric optical links, especially in terms of performance.

3

Optimal threshold detection for Málaga turbulent optical links

Jurado-Navas A., Garrido-Balsells J. M., Castillo-Vázquez M., Puerta-Notario A., Monroy I. T., Olmos J. J. V.

Optica Applicata

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2016

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Vol. 46, nr 4

577--595

EN

A new and generalized statistical model, called Málaga distribution (M distribution), has been derived recently to characterize the irradiance fluctuations of an unbounded optical wave front propagating through a turbulent medium under all irradiance fluctuation conditions. As great advantages associated to that model, we can indicate that it is written in a simple tractable closed-form expression and that it is able to unify most of the proposed statistical models for free-space optical communications derived until now in the scientific literature. Based on that Málaga model, we have analyzed in this paper the role of the detection threshold in a free-space optical system employing an on-off keying modulation technique and involved in different scenarios, and taking into account the extinction ratio associated to the employed laser. First we have derived some analytical expressions for the lower-bound performance of the free-space optical system with the light intensity fading induced by turbulence obtained when the additive white Gaussian noise is not present in the system. Then, we have analyzed the optimal threshold in the system and how it changes when atmospheric conditions vary. Finally, a closed form expression for the bit error rate of that system is derived.

4

Laser frequency stability estimation and velocity measurement in the atmosphere with self-heterodyne

Zhang H., Wang H., Zhao S.

Optica Applicata

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2016

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Vol. 46, nr 2

305--316

EN

We present a novel method of self-heterodyne for laser frequency stability estimation in the atmosphere. At the same time, it is used in the Doppler velocity measurement for moving targets in the atmosphere. The transmission range is 16.2 km (round-trip propagation with 8.1 km) in the horizontal atmospheric path, and the measuring results showed that the frequency stability of the whole laser detection system is 53.4 kHz with 20.7 kHz stand deviation. This frequency stability is the integrated influence with the whole detection system not just for the laser, but it can be considered as the estimation of the laser’s frequency stability. It is much more practical for the heterodyne detection in the atmosphere. At last, the method of self-heterodyne was used for 16.2 km round trip velocity measurement. It is showed that the velocity absolute error is less than 1.5 cm/s in the turbulent atmosphere, and the relative error is not higher than 5%.