Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651

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Start date: 2010Institution Author: search.filters.institutionAuthor.Baykal, Yahya

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Now showing 1 - 10 of 43
  • Article
    Citation - WoS: 1
    Scintillation Index in Non-Kolmogorov Jet Engine Exhaust Turbulence
    (IOP Publishing Ltd, 2026) Baykal, Yahya
    In a non-Kolmogorov jet engine exhaust turbulence environment, scintillation index is found and evaluated. Effects of non-Kolmogorov turbulence spectrum, i.e., power law on the scintillations are studied. Variations of the scintillations against the change in the power law are found for various link lengths, structure constants, wave numbers, jet engine exhaust turbulence strengths, source sizes and scale parameters of jet engine exhaust turbulence. When the power law of non-Kolmogorov turbulence varies, the changes in the scintillations in jet engine exhaust turbulence are not large. The results in this paper could be of help to designers of optical wireless communication systems operating in atmosphere experiencing non-Kolmogorov jet engine exhaust turbulence.
  • Article
    Transmittance of Gaussian Beam in Anisotropic Jet Engine Exhaust Turbulence
    (Pergamon-Elsevier Science Ltd, 2026) Baykal, Yahya
    Transmittance is a metric that provides information on how much of the intensity is transferred to the receiver for a given medium. One of the definitions of transmittance is the ratio of the average received intensity in the presence of turbulence to the received intensity in the absence of turbulence. Under such definition, transmittance is found in an anisotropic jet engine exhaust turbulent environment. For various receiver points, transmittances versus the wireless optical communication (WOC) link and anisotropic jet engine exhaust turbulence parameters are presented. The results are useful for designers of WOC links that are installed in the premises such as the airports that possess jet engine exhaust turbulence.
  • Conference Object
    Citation - WoS: 2
    Flat-Topped Field Correlations in Extremely Strong Turbulence
    (Electromagnetics Acad, 2011) Baykal, Yahya Kemal; Baykal, Yahya; Elektrik-Elektronik Mühendisliği
    In extremely strong turbulent horizontal atmospheric optical links, field correlations of flat-topped Gaussian incidence are evaluated. Field correlations are represented versus the diagonal distance at the receiver plane, for variations in the number of beams forming the flat-topped structure, receiver points, source sizes, link lengths, structure constants and the wave-lengths. Our results in extremely strong turbulence are compared to their free space counterparts which only reflect the diffraction patterns at the receiver plane. The effects of the inner scale of turbulence on the field correlations in extremely strong turbulence are examined in detail and it is observed that the size of the inner scale in extremely strong turbulence can considerably influence the field correlations of flat-topped beams.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 1
    Off-Axis Field Correlations in Turbulence
    (Ieee, 2013) Baykal, Yahya Kemal; Baykal, Yahya; Elektrik-Elektronik Mühendisliği
    The field correlations in atmospheric turbulence are evaluated for off-axis optical incidence. Within the practical range of the source and the medium parameters, increase in the diagonal length at the receiver plane is found to decrease the off-axis field correlations in turbulence. At a fixed diagonal length at the receiver plane, off-axis beams that have smaller displacement parameters and larger source sizes possess larger field correlations. When the field correlations of the off-axis beams in atmospheric turbulence are compared to their no turbulence counterparts, it is observed that the behaviour of the field correlation variations do not change, however the field correlations in turbulence diminish at smaller diagonal lengths.
  • Conference Object
    Effects of Focusing on Scintillations of Higher Order Laser Modes in Non-Kolmogorov Turbulence
    (Electromagnetics Acad, 2014) Baykal, Yahya Kemal; Baykal, Yahya; Elektrik-Elektronik Mühendisliği
    The scintillation index of focused higher order laser beam propagating in non-Kolmogorov atmospheric turbulence is formulated by employing the Rytov method and the equivalence of the structure constant. Our evaluations are performed for even modes. The equivalence formula for the structure constant is extracted from our earlier work in which the equivalence is obtained by equating the scintillation indices found in the Kolmogorov and the non-Kolmogorov turbulence. If not specified otherwise, the focused beam is defined when the focal length is equal to the link length. For the focused higher order laser beams, as the power law exponent of the non-Kolmogorov spectrum decreases, the scintillations decrease. At any power law exponent, the scintillations tend to become larger when the mode order of the focused beam becomes larger, i.e., the focused Gaussian beam is advantageous over the focused higher order laser beams for any realization of the non-Kolmogorov turbulence. Again being valid for any power law exponent, increase in the source size is found to decrease the intensity fluctuations of all the focused higher order mode scintillations. Especially for the larger order beams, focusing the higher order beam at a distance smaller than the link length results in a change in the behaviour of the scintillation index versus the power law exponent. In such cases, the scintillations are observed to increase. Comparison of the focused higher order beam scintillations with the previously obtained collimated higher order beam scintillations yields that the focused higher order beam scintillations are lower. Collimated higher order beams exhibit lower scintillations than the collimated Gaussian beams whereas this is reversed in the focused case. Another observation in such comparison shows that the difference of the intensity fluctuations between the Gaussian and the higher order beams are much larger in the focused case, especially at larger power law exponent values.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Optical Wireless Sensor Networks in Underwater Turbulence Using Multimode Beams
    (Elsevier Sci Ltd, 2025) Baykal, Yahya
    Optical wireless sensor networks (OWSN) that employ multimode optical beams operating in underwater turbulence are investigated. For this purpose, off-axis average intensity at the destination point (receiver) is formulated in underwater turbulence when the incidences at the sensors are multimode optical beams. Based on the trends of the appropriately determined off-axis received average intensities of various multimode beams, identification of the sensor can be made. The proposed procedure is also applied as special cases, to optical wireless sensor networks that employ single higher mode beams.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 1
    Degradation of Signal-To Ratio Due To Turbulence in Various Biological Tissues
    (Iop Publishing Ltd, 2024) Baykal, Yahya
    When a biological tissue is excited by an optical beam, the presence of turbulence in the tissue causes the signal-to-noise ratio (SNR) to degrade. This degradation is in reference to the SNR value in the absence of tissue turbulence. The effect of tissue turbulence in reducing the SNR is examined. SNR reductions are examined for various types of biological tissues such as liver parenchyma (mouse), intestinal epithelium (mouse), upper dermis (human). Also, SNR reductions in the turbulent tissue are evaluated against the changes in the strength coefficient of the refractive-index fluctuations, fractal dimension, characteristic length of heterogeneity, small length-scale factor, tissue length, wavelength and the source size.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Field Correlations of a Partially Coherent Optical Gaussian Wave in Tissue Turbulence
    (Optica Publishing Group, 2022) Baykal, Yahya
    For a partially coherent Gaussian optical wave, field correlations in turbulent tissues are examined. Changes in the field correlations are evaluated when the degree of source coherence, diagonal length from the receiver point, transverse receiver coordinate, tissue type, tissue length, source size, characteristic length of heterogeneity, strength coefficient of the refractive-index fluctuations, fractal dimension, and the small length-scale factor of the turbulent tissue vary. Investigated turbulent tissue types are liver parenchyma (mouse), upper dermis (human), intestinal epithelium (mouse), and deep dermis (mouse). For all the examined tissue types, field correlations are found to increase as the degree of source coherence, fractal dimension, and small length-scale factor increase and as the diagonal length from the receiver point, transverse receiver coordinate, tissue length, characteristic length of heterogeneity, and strength coefficient of the refractive-index fluctuations decrease. For the coherent source, an increase in the source size will increase the field correlations; however, for the partially coherent source, this trend is reversed. (c) 2022 Optica Publishing Group
  • Article
    Citation - WoS: 7
    Citation - Scopus: 6
    Adaptive Optics Correction of Beam Spread in Biological Tissues
    (Pergamon-elsevier Science Ltd, 2022) Baykal, Yahya
    Beam spread in turbulent biological tissues is examined when the tissue is excited with a collimated Gaussian laser beam. Adaptive optics correction is applied to the beam spread in the form of piston only (P Only), tilt only (T Only), piston + tilt (P + T), and the reduction in the beam spread is evaluated as com-pared to the no adaptive optics (No AO) corrected beam spread. No AO and adaptive optics corrected beam spread are expressed for various biological tissue types, against the variations in the strength co-efficient of the refractive-index fluctuations, source size, small length-scale factor of turbulence, tissue length, fractal dimension, characteristic lengths of heterogeneity and the wavelength. For the examined tissue types of liver parenchyma (mouse), intestinal epithelium (mouse), upper dermis (human) and deep dermis (mouse), No AO beam spread and the adaptive optics corrected beam spread are found to increase as the strength coefficient of the refractive-index fluctuations, tissue length, fractal dimension, the char-acteristic lengths of heterogeneity increase, and to decrease as the source size, small length-scale factor, wavelength increase. Reduction ratio of P + T correction is almost the same for all the evaluated cases which is 74%.(C) 2022 Elsevier Ltd. All rights reserved.
  • Editorial
    Citation - WoS: 1
    Citation - Scopus: 1
    Editorial: Optical Wave Propagation and Communication in Turbulent Media
    (Frontiers Media Sa, 2023) Baykal, Yahya