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4-aperture differential image motion monitor as a new approach for estimating atmospheric turbulence parameters
摘要： The present study aims to evaluate the possibility of simultaneous measurements of Fried parameter and atmospheric Zernike defocus by measuring defocus aberration with 4-aperture differential image motion monitor (DIMM) for a portable telescope. Based on the results, a relation was observed between the variances of the defocus aberration (4-aperture defocus) and Fried parameter for G-tilt and Z-tilt methods. In addition, the variance of the 4-aperture defocus was compared with those of the Zernike defocus and the conventional DIMM and the results indicated a linear relationship. Based on the telescope and 4-aperture specifications, the variance of the 4-aperture defocus was converted into the Zernike defocus or the DIMM variances. Finally, the ability of estimating atmospheric coherence time by measuring the variance of the Zernike defocus velocity or the sum of the variances of two astigmatisms velocities with 4-aperture DIMM was investigated.
关键词： atmospheric defocus aberration,atmospheric turbulence parameters,Optical turbulence
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 30th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) - Istanbul, Turkey (2019.9.8-2019.9.11)] 2019 IEEE 30th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) - Transmit Laser Selection for Underwater Visible Light Communication Systems
摘要： Visible light communication (VLC) has the potential to serve as a high-speed underwater wireless connectivity solution to support real-time image and video transmission. Underwater propagation medium imposes additional challenges on the design of VLC systems which were originally proposed for indoor applications. Temperature and salinity fluctuations result in fluctuations of the refractive index of seawater and eventually introduce turbulence-induced fading. In this paper, to mitigate the effects of fading, we propose transmit laser selection for a diver-to-diver underwater VLC link where the transmitter has multiple laser sources and the receiver has one photodetector. The source with the highest received instantaneous signal-to-noise ratio is selected for transmission while the remaining sources remain idle. We derive a closed-form expression for asymptotical bit error rate over log-normal distributed underwater turbulence channels and derive the achievable diversity order. We further present simulation results to confirm our derivations and diversity gain analysis.
关键词： bit error rate performance,underwater optical turbulence,transmit laser selection,diversity order,Underwater visible light communication
更新于2025-09-16 10:30:52
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Complexity in Biological and Physical Systems - Bifurcations, Solitons and Fractals || Self-Organization, Coherence and Turbulence in Laser Optics
摘要： In the last decades, rapid progress in modern nonlinear science was marked by the development of the concept of dissipative soliton (DS). This concept is highly useful in many different fields of science ranging from field theory, optics, and condensed matter physics to biology, medicine, and even sociology. This chapter aims to present a DS appearance from random fluctuations, development and growth, the formation of the nontrivial internal structure of mature DS and its breakup, in other words, a full life cycle of DS as a self-organized object. Our extensive numerical simulations of the generalized cubic-quintic nonlinear Ginzburg-Landau equation, which models, in particular, dynamics of mode-locked fiber lasers, demonstrate a close analogy between the properties of DS and the general properties of turbulent and chaotic systems. In particular, we show a disintegration of DS into a noncoherent (or partially coherent) multisoliton complex. Thus, a DS can be interpreted as a complex of nonlinearly coupled coherent “internal modes” that allows developing the kinetic and thermodynamic theory of the nonequilibrious dissipative phenomena. Also, we demonstrate an improvement of DS integrity and, as a result, its disintegration suppression due to noninstantaneous nonlinearity caused by the stimulated Raman scattering. This effect leads to an appearance of a new coherent structure, namely, a dissipative Raman soliton.
关键词： dissipative solitons,chaos in nonlinear optical systems,generalized cubic-quintic nonlinear Ginzburg-Landau equation,dissipative Raman soliton,optical turbulence
更新于2025-09-12 10:27:22
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Incoherent Shock and Collapse Singularities in Non-Instantaneous Nonlinear Media
摘要： We study the dynamics of a partially incoherent optical pulse that propagates in a slowly responding nonlinear Kerr medium. We show that irrespective of the sign of the dispersion (either normal or anomalous), the incoherent pulse as a whole exhibits a global collective behavior characterized by a dramatic narrowing and amplification in the strongly non-linear regime. The theoretical analysis based on the Vlasov formalism and the method of the characteristics applied to a reduced hydrodynamic model reveal that such a strong amplitude-incoherent pulse originates in the existence of a concurrent shock-collapse singularity (CSCS): The envelope of the intensity of the random wave exhibits a collapse singularity, while the momentum exhibits a shock singularity. The dynamic behavior of the system after the shock-collapse singularity is characterized through the analysis of the phase-space dynamics.
关键词： non-linear waves,optical turbulence,shockwaves,partially coherent beams and pulses,Vlasov formalism,coherence,rogue waves
更新于2025-09-04 15:30:14