WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653

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Author: search.filters.author.Baykal, YahyaPublisher: search.filters.publisher.Taylor & Francis Ltd

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Now showing 1 - 10 of 23
  • Article
    Citation - WoS: 5
    Citation - Scopus: 4
    Laser Array Field Correlations in Underwater Turbulence
    (Taylor & Francis Ltd, 2022) Gokce, Muhsin C.; Baykal, Yahya; Ata, Yalcin
    In underwater turbulent medium, field correlations are found when the incidence is a laser beam array. Variations of the field correlations against the variations in the ring radius of laser array beam, number of beamlets composing the laser array, source size, underwater turbulence parameters, i.e. the ratio of temperature to salinity contributions to the refractive index spectrum, rate of dissipation of mean-squared temperature and rate of dissipation of kinetic energy per unit mass of fluid, are investigated. Field correlations of laser arrays are found to be larger than the field correlations of the single beams. The effect of underwater turbulence is to reduce the field correlation of laser arrays.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 1
    Signal-To Ratio With Adaptive Optics Compensation in Non-Kolmogorov Weak Turbulent Atmosphere
    (Taylor & Francis Ltd, 2021) Baykal, Yahya; Gokce, Muhsin Caner; Ata, Yalcin
    This study investigates the average signal-to-noise ratio < SNR > at the shot-noise limited receiver of an optical wireless communication system (OWC) that uses collimated Gaussian beam with adaptive optics correction in non-Kolmogorov weak turbulent atmosphere. < SNR > and the variation in the percentage < SNR > are calculated and the results are presented against various adaptive optics correction modes, non-Kolmogorov power-law exponent, receiver aperture size, Gaussian beam source size, photodetector quantum efficiency, electronic bandwidth, link length, and turbulence strength. Adaptive optics correction is analyzed for tilt, defocus, astigmatism, coma and trefoil modes and their variations. The effects of adaptive optics compensation are examined that cause an increase in SNR, hence improve the performance of an OWC system using collimated Gaussian beam and operating in the non-Kolmogorov weak turbulent atmosphere.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 9
    Multimode Laser Beam Scintillations in Weak Atmospheric Turbulence for Vertical Link Laser Communications
    (Taylor & Francis Ltd, 2022) Sayan, Omer F.; Gercekcioglu, Hamza; Baykal, Yahya
    Scintillation index of multimode laser beams used for communication systems in vertical paths of weak atmospheric turbulent medium are examined by employing the Rytov method. On-axis scintillation index is examined versus the source size, propagation distance and zenith angle for vertical link including uplink and downlink. At the selected values of source sizes and propagation distances, scintillation responses of multimode laser beams are evaluated. In general, it is found for both uplink and downlink that the laser beam with multimode content has larger scintillation noise as compared to a Gaussian laser beam. However, for the downlink at L=700 km, at the chosen parameters, the multimode beam possessing larger mode content, is found to attain slightly smaller scintillations.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 6
    Intensity Correlation of Collimated Gaussian Beams Propagating in Biological Tissues
    (Taylor & Francis Ltd, 2021) Baykal, Yahya
    Intensity correlations in turbulent biological tissues are evaluated when collimated Gaussian laser beam is used. Variations of the intensity correlations in biological tissues are investigated versus the diagonal distance from the origin of the observation plane for various tissue distances, biological tissue types, strength coefficients of the refractive-index fluctuations, starting points at the observation plane. Also, intensity correlations in biological tissues for various biological tissue types versus the strength coefficient of the refractive-index fluctuations, small length-scale factor, fractal dimension. It is found that intensity correlations become smaller at larger diagonal distance, tissue distance, strength coefficients of the refractive-index fluctuations, and at smaller source size, small length-scale factor and fractal dimensions. Behaviour of the intensity correlations is found to depend on the type of the biological tissue. Our results can be used in tissue identification and to find the disorders in biological tissues.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 5
    Effects of Underwater Turbulence on Average Transmittance of Cos-Gaussian and Cosh-Gaussian Optical Beams
    (Taylor & Francis Ltd, 2021) Baykal, Yahya; Keskin, Aysan
    The impacts of underwater turbulence on the average optical transmittance are investigated when optical cosine-Gaussian and optical cosine-hyperbolic-Gaussian (cosh-Gaussian) beam propagate in weakly turbulent underwater medium. Findings obtained by using MATLAB reveal that when the displacement parameter is smaller (larger) for the cos-Gaussian (cosh-Gaussian) beam, the average transmittance increases. Also, an increase in the source size results in elevated average transmittance values. Rate of dissipation of kinetic energy per unit mass of fluid is found to be directly proportional to the average transmittance. However, the rate of dissipation of the mean-squared temperature is inversely proportional to the average transmittance. Average transmittance is found to be essentially the same when the temperature-induced optical turbulence is dominant. An increase in the salinity-induced optical turbulence suddenly reduces the average transmittance of the cos-Gaussian and cosh-Gaussian beam in underwater turbulence. Finally, it is observed that for the same sized beams in the same underwaterturbulent medium, cosh-Gaussian beam will have larger average transmittance than the corresponding cos-Gaussian beam. As the influence and value of our research conclusion on the development of our research, we comment that cosh-Gaussian beams can be preferred over the cos-Gaussian and Gaussian beams in obtaining larger average transmittance in underwater turbulence.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Ber Performance Ofm-Ary Pulse Position Modulated Communication Systems in Anisotropic Non-Kolmogorov Turbulent Atmosphere
    (Taylor & Francis Ltd, 2022) Gokce, Muhsin Caner; Ata, Yalcin; Baykal, Yahya
    We investigated the effect of anisotropic non-Kolmogorov atmospheric turbulence on the performance of the optical wireless systems whenM-ary Pulse Position Modulation (PPM) is applied to a Gaussian beam. The performance of the optical wireless systems that use avalanche photodetector at the receiver is evaluated in terms of the bit error rate (BER). The effects of the parameters, such as the anisotropy factors inx-ydirections, modulation order, data bit rate, equivalent load resistor, photodetector quantum efficiency, non-Kolmogorov turbulence power law exponent, beam source size, link length, photodetector gain and structure constant on BER of theM-ary PPM Gaussian beam propagating in anisotropic non-Kolmogorov atmospheric turbulence, are examined.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 5
    Anisotropic Non-Kolmogorov Turbulence Effect on Transmittance of Multi-Gaussian Beam
    (Taylor & Francis Ltd, 2020) Ata, Yalcin; Baykal, Yahya
    The effect of anisotropic non-Kolmogorov turbulent atmosphere on multi-Gaussian beam is investigated and the results are presented against different beam and medium parameters. Results show that anisotropy increases the power efficiency of wireless communication systems. Besides anisotropy, turbulence effects on the multi-Gaussian optical beam are represented versus the beam source size, beam flatness order, propagation distance, inner scale length, turbulence strength, non-Kolmogorov turbulence power law exponent, wavelength, inner and outer source sizes for flat-topped and annular beams.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Intensity Correlations of Flat-Topped Beams in Oceanic Turbulence
    (Taylor & Francis Ltd, 2020) Baykal, Yahya
    Intensity correlations of flat-topped beams are formulated and evaluated in oceanic turbulence. Variations of the intensity correlations are examined against the diagonal distance from different starting points at the receiver plane, for the various number of beams composing the flat-topped beam, for various starting points at the receiver and for various source sizes. Also, the variations of the intensity correlations are investigated against the ratio of temperature to salinity contributions to the refractive index spectrum for the various number of beams composing the flat-topped beam, against the rate of dissipation of mean-squared temperature for various starting points at the receiver plane and against the rate of dissipation of kinetic energy per unit mass of fluid for various source sizes.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 8
    M-Ary Pulse Position Modulation Performance With Adaptive Optics Corrections in Atmospheric Turbulence
    (Taylor & Francis Ltd, 2020) Gokce, Muhsin C.; Baykal, Yahya; Ata, Yalcin
    The performance of M-ary pulse position modulated (PPM) optical wireless communication (OWC) systems in atmospheric weak turbulence medium is evaluated by using adaptive optics corrections. Piston, tilt, defocus and coma components of adaptive optics corrections are applied to the avalanche photodetector (APD) type of receiver and the results are obtained depending on various turbulence and receiver parameters. The lognormal channel distribution is used to model the weak atmospheric turbulence conditions. Adaptive optics correction increases the bit-error-rate (BER) performance of an OWC system operating in atmospheric turbulence conditions. Piston component yields the highest BER performance, followed by the tilt, defocus and coma adaptive optics correction components respectively.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 13
    Field Correlation of Flat-Topped Beams in Anisotropic Non-Kolmogorov Turbulent Atmosphere
    (Taylor & Francis Ltd, 2019) Baykal, Yahya; Ata, Yalcin
    Field correlation of flat-topped beams in anisotropic non-Kolmogorov turbulent atmosphere is formulated and evaluated. Larger anisotropic factor causes higher field correlations. Smaller field correlations are seen when the transverse distance at the receiver plane increases. Smaller field correlations are observed at large off-axis transverse receiver points, which are valid for any anisotropic factor and for any power-law exponent of non-Kolmogorov turbulence. When the flat-topped beam is composed of large number of Gaussian beams, the field correlation becomes smaller. In anisotropic non-Kolmogorov turbulence, longer propagation distances, larger structure constants, smaller inner scales and smaller source sizes decrease the field correlation. Larger power law exponent of non-Kolmogorov turbulence increases the field correlations at any anisotropic factor.