Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
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Article Mitigation of Laser Beam Fluctuation and Performance of Probability of Fade in Weak Ocean Turbulence(Pergamon-Elsevier Science Ltd, 2026) Gercekcioglu, Hamza; Baykal, YahyaUtilizing the Rytov method in weakly turbulent oceanic medium, minimum scintillation index of sinusoidal Gaussian (SG) laser beams, named as the optimum beam (OB), is investigated for the underwater wireless optical communication (UWOC). Horizontal link between any underwater vehicles is considered. The formulation of the on-axis scintillation index of these beams is derived analytically, and the minimum scintillation index is determined with suitable adjustment of the complex displacement parameters. The complex displacement parameters are identified and tabulated for the selected propagation distance and source size. Obtained scintillation index results are drawn against the propagation length and source size. When compared with the plane, spherical, collimated, focused Gaussian, cos-Gaussian and cosh-Gaussian beams, OB is found to possess essential advantage. Additionally, with the obtained scintillation index values, probabilities of fade of these beams are calculated and their behaviors are also presented. OB also has a significant advantage when considering the fade probability.Article Citation - Scopus: 1Multimode Laser Beam Field Correlations for Vertical Links Operating in Oceanic Turbulence(IEEE-Inst Electrical Electronics Engineers inc, 2025) Gercekcioglu, Hamza; Baykal, Yahya; Gokce, Muhsin Caner; Caner Gokce, MuhsinIn underwater optical vertical link medium, based on the extended Huygens-Fresnel principle, multimode laser beam field correlation is derived and evaluated analytically in the Atlantic Ocean at high latitude and high latitude- low latitudes. With the depth of seawater, the coherence length of a spherical wave operating in the underwater turbulent medium is demonstrated for the range of 0-4000 m. By utilizing the coherence length varying with parameters such as the rate of dissipation of turbulent kinetic energy per unit mass of fluid epsilon, the rate of dissipation of the mean squared temperature chi(T) and non-dimensional representing the relative strength of temperature and salinity fluctuations omega, which depend on depth, the field correlation is examined in detail for single modes and multimode. Their variations are exhibited. Our results indicate clearly that as the mode increases, field correlation gets better.Article Citation - WoS: 1Citation - Scopus: 1Scintillations of Higher-Order Optical Beams in Biological Tissues(Optica Publishing Group, 2025) Baykal, Yahya; Gokce, Muhsin Caner; Ata, Yalcin; Gercekcioglu, HamzaThe Scintillation index of a higher-order laser beam in turbulent biological tissue is formulated and evaluated. Behaviors of the scintillation indices of various higher-order beams against the tissue turbulence parameters of the strength coefficient of the refractive index fluctuations, fractal dimension, characteristic length of heterogeneity, small length-scale factor, and the source size, tissue length, and wavelength are examined. Fluctuations in the intensity are also investigated when various types of tissues, such as the intestinal epithelium (mouse), liver parenchyma (mouse), and upper dermis (human), are excited by different higher-order laser beams. (c) 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: 3Citation - Scopus: 3Field Correlations of Multimode Optical Beams in Underwater Turbulence(Optica Publishing Group, 2024) Baykal, Yahya; Gokce, Muhsin C.; Ata, Yalcin; Gercekcioglu, HamzaFor multimode optical beams, field correlations at the receiver plane are found in underwater turbulence. Field correlations of single high order beams in underwater turbulence are special cases of our formulation. Variations of field correlations against the underwater turbulence parameters and the diagonal length from various receiver points are examined for different multimode and single high order beams. Stronger underwater turbulence is found to reduce the field correlations of multimode and single high order optical beams. The results will be of help in heterodyne detection analysis and fiber coupling efficiency in an underwater medium experiencing turbulence. (c) 2024 Optica Publishing GroupArticle Citation - WoS: 5Citation - Scopus: 6Bit Error Rate of M-Pulse Position Modulated Laser Beams for Vertical Links Operating in Weak Oceanic Turbulence(Iop Publishing Ltd, 2024) Gercekcioglu, Hamza; Baykal, YahyaThe on-axis scintillation index of laser beams is investigated by employing the Rytov method in a weakly turbulent oceanic medium for up/downlink coupling of laser communication between any underwater vehicles or divers. For vertical links, the formulation of the on-axis scintillation index of laser beams is derived analytically and evaluated for plane, collimated Gaussian and spherical beams in specific mediums, including the Atlantic Ocean at mid and low latitudes associating temperature and salinity changes at low latitudes, at mid latitude-summer and at mid latitude-winter. Using the scintillation index, bit error rate (BER) performance of M-pulse position modulation is investigated for these types of laser beams. The variations of the scintillation index against the uplink/downlink propagation distances, source size and zenith angle are examined, and BER variations versus the Kolmogorov microscale and the symbol orders, and results are compared. It is noted that the behavior of the scintillation index that depends on the relative strength of temperature and salinity fluctuations which changes in depth, is different for uplink/downlink and for each latitude due to its distinct characteristics. The source size that minimizes the scintillation index values is in the range of about 0.1 cm-0.2 cm for all latitudes.Article Citation - WoS: 4Citation - Scopus: 4Intensity and Degree of Coherence of Vortex Beams in Atmospheric Turbulence(Ieee-inst Electrical Electronics Engineers inc, 2024) Gokce, Muhsin Caner; Baykal, Yahya; Gercekcioglu, Hamza; Ata, Yalcin; Caner Gokce, MuhsinWe utilize the Huygens-Fresnel principle to derive the mutual coherence function (MCF) for a vortex beam, which is the main focus of our investigation. Then, we examine the intensity and modulus of the complex degree of coherence (DOC) characteristics of vortex beams in atmospheric turbulence. Our results indicate that as the topological charge increases, the intensity distribution of the vortex beam becomes less affected by atmospheric turbulence. However, the modulus of the complex DOC decreases.Article Citation - WoS: 1Citation - Scopus: 2Scintillation Index and Outage Probability of Vortex Gaussian Beams for Horizontal Links in Weak Atmospheric Turbulence(Iop Publishing Ltd, 2024) Gercekcioglu, Hamza; Baykal, YahyaUsing the Rytov method, the off-axis scintillation index for a Gaussian vortex beam is examined in horizontal laser communication links operating in a weakly turbulent atmosphere. The performance of laser communication systems, defined in this study by the outage probability, is evaluated using the lognormal distributed intensity to find the scintillation index. The off-axis scintillation index of vortex Gaussian beams is analytically derived and evaluated in horizontal atmospheric links. The scintillation index obtained from the figures drawn versus the source size and propagation length is used to calculate the outage probability. It is found that turbulence affects vortex Gaussian beams less than non-vortex Gaussian beams. Our important finding is that the scintillation index is reduced when the topological charge increases.Editorial Citation - WoS: 4Citation - Scopus: 1Intensity Fluctuations of Flat-Topped Beam in Non-Kolmogorov Weak Turbulence: Reply(Optical Soc Amer, 2012) Gercekcioglu, Hamza; Baykal, YahyaIn our recent publication, we have examined the intensity fluctuations of flat-topped beam in non-Kolmogorov weak turbulence [J. Opt. Soc. Am. A 29, 169 (2012)] in which our comparison of the scintillation indices in the Kolmogorov and in various non-Kolmogorov turbulences was based on the same structure constant, no matter what power law the non-Kolmogorov spectrum takes. In such choice of the fixed structure constant, which is also being used by many researchers in the field [Opt. Express 18, 451 (2010); Proc. SPIE 6747, 67470B (2007); Opt. Commun. 285, 880 (2012)], we have found that the variation of the scintillation index against non-Kolmogorov power law exhibits a peak at the worst power law, which happens to be smaller than the Kolmogorov power law of 11/3. Charnotskii commented [J. Opt. Soc. Am. A. 29, 1838 (2012)] on our paper. In this paper, in our to reply to Charnotskii's comment, we have re-evaluated the scintillation index of flat-topped beam in non-Kolmogorov weak turbulence by employing our recently reported equivalent structure constant [Opt. Lett. 36, 4554 (2011)] and re-compared the intensity fluctuations in Kolmogorov and in non-Kolmogorov turbulences. As the result of such re-comparison, the worst power law is observed to disappear. c 2012 Optical Society of AmericaArticle Citation - WoS: 11Citation - Scopus: 9Multimode Beam Propagation Through Atmospheric Turbulence(Pergamon-elsevier Science Ltd, 2024) Baykal, Yahya; Ata, Yalcin; Gercekcioglu, Hamza; Gokce, Muhsin CanerThe investigation focuses on studying the propagation characteristics of multimode lasers in the turbulent amosphere. By employing the Huygens-Fresnel integral, we develop analytical formulations for various propagation parameters. These include the average intensity distribution, kurtosis parameter, beam spread, and the average transmittance of multimode beams in turbulent atmosphere. Our findings reveal that as the propagation distance or the structure constant of the atmosphere increases, i.e., turbulence becomes stronger, the kurtosis parameter and the beam spread increase. The multimode beam exhibits a Gaussian like intensity profile when the propagation distance is significantly increased or when the structure constant becomes sufficiently large. For the case of the Gaussian beam, the kurtosis parameter is found to be 3. The multimode beam's kurtosis parameter rises as the turbulence becomes stronger and eventually approaches 3. Raising the mode content leads to a rise in the average transmittance; however, it leads to a decline in the Kurtosis parameter and the beam spread.Article Citation - WoS: 3Citation - Scopus: 5Depth Dependence of Oceanic Turbulence Optical Power Spectrum Under Any Temperature and Salinity Concentration(Iop Publishing Ltd, 2024) Gercekcioglu, Hamza; Baykal, YahyaThe Oceanic Turbulence Optical Power Spectrum (OTOPS) with depth variations is acquired under any temperature and salinity concentration. It is supposed that specific medium is the Atlantic Ocean at high latitude and the Pacific Ocean at high, mid and low latitudes. For the OTOPS model, a depth-varying functions that include low-latitude, high- and mid-latitude-summer and mid-latitude-winter salinity and temperature changes are found. With the help of the equations for the temperature and salinity changes, figures are obtained for the eddy diffusivity ratio depth of seawater and OTOPS model against the depth and kappa at these media. In the ocean, downlink (uplink) is defined as the optical wireless communication link where the receiver (transmitter) is located at a deeper point than the transmitter (receiver), i.e., in the downlink, optical signal proceeds from a point close to ocean surface to deeper ocean and in the uplink, optical signal proceeds from deeper ocean to a point close to ocean surface. In this paper, the OTOPS model is investigated on how its properties change in the underwater environment in downlink and uplink. Different behavior of the OTOPS model is exhibited.
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