Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/411
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Article Citation - WoS: 9Citation - Scopus: 8Effect of Partial Coherence on Signal-To Ratio Performance of Free Space Optical Communication System in Weak Turbulence(Elsevier, 2022) Aymelek, Goerkem; Yolcu, Beguem; Kayam, Orkun; Unal, Onur; Caner Gokce, Muhsin; Baykal, Yahya; Akbucak, Volkan; Gökçe, Muhsin CanerThe effect of source coherence on the average signal-to-noise ratio ((SNR)) performance of free space optical communication (FSOC) systems operating in weak atmospheric turbulence is investigated with the help of the extended Huygens-Fresnel principle. For an FSOC system that uses a partially coherent laser source, first, the received power at the finite-sized receiver aperture is derived. Then, the power scintillation index is evaluated that reflects the aperture averaging. Using these derived optical entities, the variations of (SNR) are examined versus parameters such as the degree of source coherence, wavelength, link distance, source size, structure constant of atmosphere and the receiver aperture radius. Obtained results show that a decrease in the degree of source coherence has a positive effect on (SNR).Article Citation - WoS: 3Citation - Scopus: 3Laser Beam Scintillations of Lidar Operating in Weak Oceanic Turbulence(Optica Publishing Group, 2022) Baykal, Yahya; Gercekcioglu, HamzaThe formulation of light detection and ranging (LIDAR) systems is derived and examined for the scintillation index, evaluated on-axis, of laser beams in horizontal links in the ocean with weak turbulence by utilizing the Rytov method. These scintillation indices, obtained for the Gaussian beam which is collimated, the limits of plane and spherical waves, are depicted versus the source size, target size, and parameter of the normalized reflector size. It is found that the source size, target size, and normalized reflector size parameter, lessening the scintilla-tion index evaluated on-axis, are approximately 0.44 cm, 56 x 10-4 cm, and 2.2, respectively. Additionally, by using these values that minimize the scintillation index, the variation of the scintillations is shown against the propagation distance, radius of reflector, temperature and salinity fluctuation effects, mean squared temperature, and turbulent kinetic energy dissipation rate per unit mass of fluid at various selected source size and radius of reflector values. (c) 2022 Optica Publishing GroupArticle Citation - WoS: 106Citation - Scopus: 115Effect of Eddy Diffusivity Ratio on Underwater Optical Scintillation Index(Optical Soc Amer, 2017) Elamassie, Mohammed; Uysal, Murat; Baykal, Yahya; Abdallah, Mohamed; Qaraqe, KhalidThe performance of underwater optical wireless communication systems is severely affected by the turbulence that occurs due to the fluctuations in the index of refraction. Most previous studies assume a simplifying, yet inaccurate, assumption in the turbulence spectrum model that the eddy diffusivity ratio is equal to unity. It is, however, well known that the eddy diffusivities of temperature and salt are different from each other in most underwater environments. In this paper, we obtain a simplified spatial power spectrum model of turbulent fluctuations of the seawater refraction index as an explicit function of eddy diffusivity ratio. Using the derived model, we obtain the scintillation index of optical plane and spherical waves and investigate the effect of the eddy diffusivity ratio. (C) 2017 Optical Society of AmericaArticle Citation - WoS: 22Citation - Scopus: 23Scintillations of Higher Order Laser Beams in Anisotropic Atmospheric Turbulence(Optical Soc Amer, 2016) Baykal, Yahya; Luo, Yujuan; Ji, XiaolingThe scintillation index of higher order laser beams is examined when such beams propagate in anisotropic atmospheric turbulence. Anisotropy is introduced through non-Kolmogorov atmospheric turbulence. The scintillation index results are obtained by employing the Rytov method solution; thus the results are valid for weak anisotropic atmospheric turbulence and for horizontal links. Variations in the scintillations are shown for various higher order laser modes against the changes in the optical source size, power law exponent of anisotropic non-Kolmogorov spectrum, anisotropic factors, and link length. Our results can be used in the design of optical wireless communication systems used between airplanes. (C) 2016 Optical Society of America