WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653
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Article Scintillation Characteristics of Annular Beam Array in Underwater Optical Links(IOP Publishing Ltd, 2025) Erdogdu, Ekin; Gokce, Muhsin Caner; Baykal, YahyaUnderwater optical wireless communication systems offer a promising alternative to traditional acoustic methods for achieving high data rate transmission. However, the propagation of optical waves in underwater environments is severely impacted by oceanic turbulence, leading to intensity fluctuations and consequent performance degradation. In this work, we employ a laser beam array to model transmit spatial diversity for suppressing these fluctuations. The model uses annular-shaped lasers at the transmitter as a representation of beam shaping for turbulence mitigation, with a point detector assumed at the receiver. Through the use of the Huygens-Fresnel principle, we derive two key optical parameters: the average received intensity and the average of the intensity squared. We subsequently determine the scintillation index for this model. Our findings demonstrate reductions in scintillation under varying system parameters. For instance, increasing the number of beams in the array, the ring radius, and the secondary field amplitude of the annular beam leads to a lower scintillation index.Article Effects of Receiver Diversity on Bit Error Rate of Underwater Optical Wireless Communication Systems in Weak Oceanic Turbulence(Springer, 2025) Gokce, Muhsin Caner; Baykal, Yahya; Ata, YalcinThe receiver spatial diversity techniques are employed in underwater optical wireless communication (OWC) systems to mitigate oceanic turbulence, improving the bit error rate performance. In this paper, we consider an OWC system employing a binary phase-shift keying (BPSK) modulated Gaussian beam at the transmitter and employing receiver spatial diversity at the receiver. The techniques for receiver spatial diversity systems considered in the study are selection combining (SC), equal gain combining (EGC), and the maximum ratio combining (MRC). The bit error rate (BER) performance of the OWC system operating in weak oceanic turbulence is investigated by calculating the Gaussian beam's turbulence-induced scintillation index and the received optical intensity. It is found that the receiver spatial diversity techniques, especially EGC and MRC, are very effective for reducing the BER of an OWC system in weak oceanic turbulence. Furthermore, the BER performance of the underwater OWC system sees an improvement with an increase in the number of photodetectors or a decrease in the level of oceanic turbulence. Moreover, an improvement in the photodetector responsivity or a reduction in the system's noise factor contributes to achieving a favorable BER performance.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: 20Citation - Scopus: 22Analysis of Optical Wireless Mimo Communication in Underwater Medium(Ieee-inst Electrical Electronics Engineers inc, 2024) Ata, Yalcin; Baykal, Yahya; Gokce, Muhsin CanerLeveraging on the multiple-input-multiple-output (MIMO) application for enabling high data rates and ensuring reliable communication between underwater platforms connected to underwater sensor network, this article presents a comprehensive analysis of the performance of optical wireless MIMO communication systems depending on the various phenomena. The outage performance of an underwater optical wireless communication (UOWC) is obtained in analytical form using the Meijer-G function. Aysmptotic expression of outage probability is also derived for high signal-to-noise ratio (SNR) regime. Results show that the destructive combined effect of the underwater turbulence, pointing error, attenuation, and angle of arrival (AOA) on the outage performance can be reduced by applying the MIMO spatial diversity technique.Article Citation - WoS: 12Citation - Scopus: 15Intelligent Reflecting Surface Aided Vehicular Optical Wireless Communication Systems Using Higher-Order Mode in Underwater Channel(Ieee-inst Electrical Electronics Engineers inc, 2024) Ata, Yalcin; Gokce, Muhsin Caner; Baykal, YahyaInstead of traditional acoustic communication, optical wireless communication (OWC) remains as a prominent solution in terms of ensuring high data rates for underwater sensor network (USN) including autonomous underwater vehicles (AUVs), remotely operated vehicles (ROVs), submarines, and other underwater platforms. This study is devoted to the performance analysis of underwater optical wireless communication (UOWC) systems using higher-order mode optical beam source and performance improvement with the application of intelligent reflecting surface (IRS) by using realistic parameters. To make the study as comprehensive as possible, the effects of beam misalignment, attenuation (absorption- and scattering-induced), and underwater turbulence are included. The analytical expressions are obtained for probability density function (PDF), cumulative distribution function (CDF) and outage probability (OP) of UOWC channel. The benefit of IRS application is observed to attain at significant levels for UOWC.Article Citation - WoS: 4Citation - Scopus: 4Transmittance of Gaussian Beams in Biological Tissues(Pergamon-elsevier Science Ltd, 2025) Ozcan, Murat Kaan; Gokce, Muhsin Caner; Baykal, YahyaThe study examines the average transmittance of Gaussian beams passing through various biological tissues, taking into account the impact of turbulence, absorption, and scattering. The extended Huygens-Fresnel technique, which utilizes the power spectrum of turbulent biological tissues, is applied to determine the optical intensity at the observation point. Additionally, there are tabulated absorption and scattering coefficients available for the application of the Beer-Lambert law, facilitating the calculation of optical light attenuation in biological tissues. Examining the impact of turbulence, as well as absorption and scattering-induced attenuation on the Gaussian beam's propagation, the changes in transmittance are documented across different tissue parameters.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: 3Citation - Scopus: 4Adaptive Optics Compensation of M-Ary Pulse Position Modulated Communication Systems in Anisotropic Non-Kolmogorov Turbulent Atmosphere(Elsevier, 2021) Ata, Yalcin; Baykal, Yahya; Gokce, Muhsin CanerAdaptive optics compensation effect on the performance of an optical wireless communication system (OWC) employing M-ary pulse position modulation (PPM) scheme in anisotropic non-Kolmogorov turbulent atmosphere is investigated. Avalanche photodetector (APD) is used at the receiver side and log-normal channel that models the weak turbulence conditions is utilized. Anisotropy, generally resulting in better performance in OWC systems operating in the turbulent medium, combined with the adaptive optics applications will enhance the bit-error-rate (BER) of the OWC systems significantly. Results are obtained depending on various parameters for both the turbulent atmosphere and the receiver. Our work gives OWC system designers a perspective to optimize their design.Article 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.