Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
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Article Comparison of the Unmodified Rytov Method and the Modified Rytov Method in Obtaining Scintillations in Various Strongly Turbulent Media(Optica Publishing Group (Formerly OSA), 2026) Baykal, Y.The scintillation index as evaluated by the unmodified (classical) Rytov method solution for weak turbulence and evaluated by the modified or the extended Rytov method solution for strong turbulence is compared in different turbulent media, such as non-Kolmogorov atmospheric, non-Kolmogorov jet engine exhaust, marine atmospheric, and oceanic turbulences. When the scintillations are evaluated against the turbulence strength for various non-Kolmogorov power law and source sizes, the distinction between the modified Rytov and the unmodified Rytov method solutions, as the strength of turbulence increases, is clearly observed in all the turbulent media. This distinction is emphasized when the comparison is made at larger power law and source sizes. The results in this paper will be helpful in optical wireless communication system performance evaluations. © 2025 Optica Publishing Group.Article Field Correlations of a Gaussian Vortex Laser Beam in Vertical Turbulent Oceanic Links(Optica Publishing Group (Formerly OSA), 2026) Gerçekcioǧlu, H.; Baykal, Y.Utilizing the extended Huygens–Fresnel principle, field correlations of a Gaussian vortex beam propagating in the vertical turbulent oceanic link are examined analytically and evaluated by simulation in the Atlantic Ocean at low- and mid-latitude and high-latitude summer. Our formulation is based on the coherence length of a spherical wave operating at the depth range between 3000 and 3500 m. Variations in the rate of dissipation of turbulent kinetic energy per unit mass of fluid ε, the rate of dissipation of the mean-squared temperature χT, and the ratio of temperature to salinity contributions to the refractive index spectrum ω are taken into account at these depths in the underwater turbulent medium. The field correlation obtained using the coherence length found with the help of the depth-dependent power spectrum is expressed in detail. When the topological charge is selected considering the source size and propagation distance, it is seen that the normalized field correlation of the Gaussian vortex beam gives better results as compared to Gaussian beams. © 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.Article Citation - WoS: 1Citation - Scopus: 1Optical Wireless Communication in Atmosphere and Underwater: Statistical Models, Improvement Techniques, and Recent Applications(Institute of Electrical and Electronics Engineers Inc., 2026) Ata, Y.; Al-Sallami, F.M.; Gökçe, M.C.; Vegni, A.M.; Rajbhandari, S.; Baykal, Y.Optical Wireless Communication Systems (OWCSs) are becoming more popular each day, especially after numerous mobile applications are being employed within the concept of Internet of Things (IoT). OWCSs are largely used in both terrestrial and non-terrestrial environments, like underwater, air, and space scenarios. Due to the large applicability of OWCS, it represents one of the main candidate technologies for the future 6G wireless communication systems. Naturally, this market trend forces the system designers to reach the best performance in their designs, as well as optimize the cost. In this survey paper, we intend to provide information to the researchers working in this field on the statistical models adopted in OWCS, the methods and techniques used to improve their performances, mainly in outdoor environment like air, space, and underwater. In this respect, the background on theoretical aspects of OWCS, together with their benefits, limitations and challenges are presented. Performance improvement techniques employed in OWCSs, such as power increase, partial coherence, beamforming, aperture averaging, spatial diversity, and intelligent reflecting surfaces, are also introduced. Finally, we discuss the open challenges that researchers are still facing, together with future directions on next steps for a large-scale adoption of OWCS. © 1998-2012 IEEE.Article Field Correlations in Jet Engine Exhaust Turbulence(Optica Publishing Group (Formerly OSA), 2026) Baykal, Y.Field correlations of collimated Gaussian beams are formulated and examined in jet engine exhaust turbulence. Variations of the field correlations are evaluated against the changes in the parameters of the wireless optical communication link and the jet engine exhaust turbulence. It is found that for all the link and turbulence parameters of interest, as the diagonal distance at the receiver plane increases, the field correlation decreases. Also, at the same diagonal distance from the receiver plane, field correlations tend to become smaller as the receiver points are at a larger distance from the receiver origin, at a smaller source size, wavelength, and inner scale values of jet engine exhaust turbulence. On the other hand, field correlations have a tendency to attain larger values at smaller link length, structure constant, amplitude coefficient for the additional high frequency spectrum area, outer scale of inhomogeneity, and the outer scale values of jet engine exhaust turbulence. © 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.Article Propagation Characteristics of Higher-Order Annular Gaussian Beams in Oceanic Turbulence(Institute of Physics, 2025) Arpali, S.A.; Arpali, Ç.; Baykal, Y.This study aims to explore the propagation characteristics of higher-order annular Gaussian (HOAG) beams in oceanic turbulence. We provide an analytical derivation of the average intensity at the receiver plane based on excitation from a HOAG source field. Additionally, we conduct a detailed analyses of various beam intensity moments including kurtosis parameter, power-in-the-bucket (PIB) and the beam size variation. As oceanic turbulence strength increases, the HOAG beam gradually transforms into a pure Gaussian beam. As the strength of turbulence increases, PIB values for all modes of HOAG beams gradually decrease in an exponential manner until they stabilize, exhibiting behavior similar to that of Gaussian beams. It is also observed that modes of HOAG beams having larger mode numbers carry less energy to the receiver compared to lower-order modes as turbulence strength increases. Analyses of the kurtosis parameter for HOAG beams indicate that during propagation over intermediate distances, there is a tendency for more beam energy to be distributed toward the wings rather than to the center. In contrast, at longer distances, the beam redistributes its energy, resulting in a lower energy concentration in the wings compared to the center. This research can enhance our understanding of the effects of higher-order laser beams, thereby potentially facilitating longer communication distances in underwater wireless optical communication technologies. © 2025 IOP Publishing Ltd.Conference Object Effects of Type of Incidence on the Second and Fourth Order Moment Parameters Evaluated in Turbulent Atmosphere(2010) Baykal, Y.; Baykal, Yahya Kemal; Elektrik-Elektronik MühendisliğiUsing a general type incidence, the second and fourth order moments are formulated in atmospheric turbulence. Received field and intensity correlations are evaluated and the behaviour of these correlations are compared for different beam types. © 2010 OSA/FiO/LS.Conference Object Citation - Scopus: 2Scintillation Index of Partially Coherent Asymmetrical Multi Gaussian Beams in Extremely Strong Turbulence(2010) Baykal, Yahya Kemal; Öztan, M.A.; Baykal, Y.; Elektrik-Elektronik MühendisliğiIt is investigated whether partial coherent asymmetrical annular and flat-topped Gaussian beams provide advantage to decrease the scintillation noise effect when free space optics systems are used in long distance (longer than 5km) transmission links. Scintillation index of partially coherent asymmetrical multi Gaussian beam propagating in extremely strong turbulence is formulated and the scintillation indexes of asymmetrical annular and flat-topped Gaussian beams are calculated. Scintillation index variations are plotted against the source size and asymmetry ratio. It is determined that asymmetric beams have advantage over the symmetric beams in terms of the scintillation. It is found that the scintillation index decreases as the asymmetry ratio increases. It is also detected that by decreasing the coherence degree scintillation index of the propagating beam quickly goes to zero.Conference Object Citation - WoS: 1Citation - Scopus: 1Scintillations in Weak Turbulence of Annular Beams Whose Individual Components Are Incoherent(Electromagnetics Acad, 2010) Eyyuboğlu, Halil Tanyer; Baykal, Y.; Eyyuboglu, H. T.; Baykal, Yahya Kemal; Cai, Y.; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik MühendisliğiThe scintillation index, arising from the intensity fluctuations in weak atmospheric turbulence of annular beams whose individual components are incoherent, is formulated. For such beams whose annularities are obtained by varying the source sizes and magnitudes of the individual beams, evaluations show that at very small sized beam structures, thinner beams possess smaller scintillations. As the sizes increase, the scintillation index values of thick and thin beams approach each other, eventually exhibiting the same scintillation behavior at large sized beam structures. Examination of the intensity fluctuations of the annular beams, whose individual incoherent components are at the same size but at different magnitudes, yield reverse behavior such that at very small sized beam structures, thicker beams possess smaller scintillations, however the scintillation values are very close to each other. Again, for large sized beams, the scintillation index values of thick and thin beams approach each other, eventually exhibiting the same scintillation behavior at large sized beam structures. Comparing the scintillation indices of annular beams whose individual components are incoherent to those of traditional annular beams of coherent components, it seems that for large sized beams, incoherently subtracted beams are advantageous, however the reverse is valid for very small sized beam structures.Conference Object Citation - WoS: 1Formulation of Scintillations for Optical Incidence of Arbitrary Field Profile(Electromagnetics Acad, 2008) Eyyuboğlu, Halil Tanyer; Baykal, Y.; Eyyuboglu, H. T.; Baykal, Yahya Kemal; Cai, Y.; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik MühendisliğiScintillation index on the receiver axis is formulated in random medium when an optical source with an arbitrary field profile is employed. To represent the arbitrary source field profile, source is decomposed into pixels and the incident field to form the scintillations is expressed as the superposition of the fields from each pixel area. Thus obtained arbitrary field distribution is then introduced into the weak atmospheric turbulence formulation by using Rytov method. Our result, which is in summa ion and integral forms, reduces correctly to the known scintillation index of a Gaussian beam wave in atmospheric turbulence.Article Citation - Scopus: 70Influence of Turbulence on the Effective Radius of Curvature of Radial Gaussian Array Beams(Optical Society of American (OSA), 2010) Ji, X.; Eyyuboglu, H.T.; Baykal, Y.The analytical formula for the effective radius of curvature of radial Gaussian array beams propagating through atmospheric turbulence is derived, where coherent and incoherent beam combinations are considered. The influence of turbulence on the effective radius of curvature of radial Gaussian array beams is studied by using numerical calculation examples. © 2010 Optical Society of America.