WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653
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Article Citation - WoS: 3Citation - Scopus: 5Performance of M-Ary Pulse Position Modulated Optical Wireless Communications Systems in the Marine Atmosphere(Optical Soc Amer, 2021) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin C.The marine atmosphere exhibits different turbulence spectrum characteristics when compared to the turbulence spectra of the land atmosphere and underwater medium. The performance of M-ary pulse position modulated (PPM) optical wireless communications (OWC) systems operating in the marine atmosphere, as measured by the bit error rate (BER), is studied here. In our investigation, the scintillation index and the average intensity in marine atmospheric turbulence are used. The variations of BER performance are reported against the marine atmospheric turbulence parameters for various values of the average current gain of the avalanche photodetector (APD), data bit rate of theOWClink, and M value of the M-ary PPM. (C) 2021 Optical Society of AmericaArticle Citation - WoS: 12Citation - Scopus: 14M-Ary Pulse Position Modulation Performance in Strong Atmospheric Turbulence(Optical Soc Amer, 2018) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin CanerThe performance of an M-ary pulse position modulated (PPM) optical wireless communication system operating in strong atmospheric turbulence is investigated. Bit error rate (BER) is employed as the measure for the performance. In our overall performance formulation, average received power as measured by a finite-sized avalanche photodiode (APD) detector is used by the help of the extended Huygens-Fresnel principle. For the aperture averaged scintillation evaluations, the asymptotic Rytov theory with the gamma-gamma intensity statistics is utilized. Gamma-gamma statistics together with the large-scale and the small-scale log-intensity variances yield the scintillation index valid both in weak and strong atmospheric turbulence regimes. BER variations versus the plane wave scintillation index are examined at different values of receiver aperture diameters, data bit rates, M values of M-ary PPM, quantum efficiency, and average APD gain. (C) 2018 Optical Society of AmericaArticle Citation - WoS: 8Citation - Scopus: 8Structure Parameter of Anisotropic Atmospheric Turbulence Expressed in Terms of Anisotropic Factors and Oceanic Turbulence Parameters(Optical Soc Amer, 2019) Ata, Yalcin; Gokce, Muhsin C.; Baykal, YahyaThe structure parameter of the anisotropic atmospheric turbulence is expressed in terms of atmospheric, oceanic anisotropic factors in x and y directions, and the oceanic turbulence parameters, which are the wavelength, the link length, the ratio of temperature to salinity contributions to the refractive index spectrum, the rate of dissipation of mean-squared temperature, and the rate of dissipation of kinetic energy per unit mass of fluid. For the purpose of expressing the structure parameter of the anisotropic atmospheric turbulence in terms of atmospheric, oceanic anisotropic factors and the oceanic turbulence parameters, the spherical wave scintillation indices that are found in weak anisotropic atmospheric turbulence and in weak oceanic turbulence are equated to each other. We aim to utilize the structure parameter expressed in this paper in the evaluations of various physical entities such as the average intensity, scintillation index, and beam spread in anisotropic oceanic turbulence by exploiting the existing solutions for the same physical entities in anisotropic atmospheric turbulence. Use of this structure parameter will help us to obtain the anisotropic oceanic turbulence results easily because such results will be found by just inserting the structure parameter expressed in this paper to the already reported corresponding results of anisotropic atmospheric turbulence. (C) 2019 Optical Society of AmericaArticle Citation - WoS: 9Citation - Scopus: 11Effect of Strong Atmospheric Non-Kolmogorov Turbulence on the M-Ary Psk Subcarrier Intensity Modulated Free Space Optical Communications System Performance(Optical Soc Amer, 2019) Baykal, Yahya; Gokce, Muhsin C.; Ata, YalcinAtmospheric turbulence is one of the significant phenomena that degrades the free space optical (FSO) communications system performance, and thus designers need to define the requirements related to turbulence and optimize the system design to ensure optimum performance. The subcarrier intensity modulation (SIM) shows superiority in terms of bandwidth usage over the other modulation techniques. Performance of FSO communication systems exercising M-ary phase-shift-keying (PSK) SIM with the PIN photodiode receiver is evaluated in non-Kolmogorov strong atmospheric turbulence when a Gaussian beam is used as the excitation. Bit-error-rate (BER) of PSK SIM FSO communication systems is examined, and the results are presented versus the non-Kolmogorov atmospheric turbulence and positive-intrinsic-negative (PIN) photodetector parameters such as PIN photodetector responsivity, equivalent load resistor, modulation order, noise factor, bandwidth, propagation distance, and beam source size. (C) 2019 Optical Society of AmericaArticle Citation - WoS: 5Citation - Scopus: 5Performance of M-Ary Pulse Position Modulation for Aeronautical Uplink Communications in an Atmospheric Turbulent Medium(Optical Soc Amer, 2019) Baykal, Yahya; Gokce, Muhsin Caner; Ata, YalcinThis paper discusses the bit-error-rate (BER) performance of an aeronautical uplink optical wireless communication system (OWCS) when a Gaussian beam is employed and the M-ary pulse position modulation technique is used in an atmospheric turbulent medium. Weak turbulence conditions and log-normal distribution are utilized. The Gaussian beam is assumed to propagate on a slant path, the transmitter being ground-based, and the airborne receiver is on-axis positioned. Variations of BER are obtained against the variations in the link length, Gaussian beam source size, zenith angle, wind speed, wavelength, modulation order, data bit rate, equivalent load resistor, avalanche photodetector gain, and detector quantum efficiency. It is observed that the performance of the aeronautical uplink OWCS is affected from atmospheric turbulence significantly. (C) 2019 Optical Society of AmericaArticle Citation - WoS: 24Citation - Scopus: 25M-Ary Pulse Position Modulation Performance in Non-Kolmogorov Turbulent Atmosphere(Optical Soc Amer, 2018) Baykal, Yahya; Gokce, Muhsin C.; Ata, YalcinThe performance of atmospheric optical wireless communication systems in terms of the bit error rate (BER) is investigated when a Gaussian laser beam propagating in non-Kolmogorov turbulence is M-ary pulse-position-modulated (PPM). BER variations against the changes in different parameters such as the non-Kolmogorov power law exponent, symbol number, data bit rate, avalanche photodetector gain, equivalent load resistor, detector quantum efficiency, wavelength, turbulence structure constant, and the Gaussian beam source size are analyzed. Making the design of the PPM optical wireless communication system able to operate in a non-Kolmogorov atmosphere will give better BER performance if the parameters are taken into account in line with the trends presented in our results. (C) 2018 Optical Society of AmericaArticle Citation - WoS: 36Citation - Scopus: 39Effect of Anisotropy on Bit Error Rate for an Asymmetrical Gaussian Beam in a Turbulent Ocean(Optical Soc Amer, 2018) Ata, Yalcin; Baykal, YahyaEffect of anisotropy on the average bit error rate (BER) is investigated when an asymmetrical Gaussian beam is propagated in an anisotropic turbulent ocean. BER is found to decrease in response to an increase in anisotropy levels in the x and y directions. Higher average signal-to-noise ratio, wavelength, and microscale length yield smaller BER values. BER starts to rise with an increase in the asymmetrical beam source size in the x and y directions, source size ratio in the x and y directions, salinity and temperature contribution factor, the dissipation of the mean squared temperature, and the propagation distance. At the fixed source size ratio in the x and y directions of the asymmetrical beam source size, larger source sizes increase BER. An anisotropic turbulent ocean seems to exhibit better BER values as compared with an isotropic turbulent ocean. (c) 2018 Optical Society of AmericaArticle Citation - WoS: 137Citation - Scopus: 151Scintillations of Optical Plane and Spherical Waves in Underwater Turbulence(Optical Soc Amer, 2014) Ata, Yalcin; Baykal, YahyaThe scintillation indices of optical plane and spherical waves propagating in underwater turbulent media are evaluated by using the Rytov method, and the variations in the scintillation indices are investigated when the rate of dissipation of mean squared temperature, the temperature and salinity fluctuations, the propagation distance, the wavelength, the Kolmogorov microscale length, and the rate of dissipation of the turbulent kinetic energy are varied. Results show that as in the atmosphere, also in underwater media the plane wave is more affected by turbulence as compared to the spherical wave. The underwater turbulence effect becomes significant at 5-10 m for a plane wave and at 20-25 m for a spherical wave. The turbulence effect is relatively small in deep water and is large at the surface of the water. Salinity-induced turbulence strongly dominates the scintillations compared to temperature-induced turbulence. (C) 2014 Optical Society of AmericaArticle Citation - WoS: 14Citation - Scopus: 15Field Correlation of Spherical Wave in Underwater Turbulent Medium(Optical Soc Amer, 2014) Ata, Yalcin; Baykal, YahyaThe absolute field correlation of the spherical wave in an underwater turbulent medium is investigated at the receiver plane by using the extended Huygens-Fresnel principle. Results denote that increase in the propagation distance, the rate of dissipation of the mean squared temperature, and microscale length cause reduction in the absolute field correlation. Field correlation increases when the wavelength and the rate of dissipation of the turbulent kinetic energy and parameters of temperature and salinity contribution to the turbulence decrease. Salinity dominated turbulence corrupts the absolute field correlation much more in comparison to the temperature dominated turbulence. Change in the receiver coordinate is found not to affect the absolute field correlation. (C) 2014 Optical Society of America