Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/411
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Article Citation - WoS: 6Citation - Scopus: 6Correlation of Multimode Fields in Atmospheric Turbulence(Optica Publishing Group, 2023) Gokce, Muhsin Caner; Ata, Yalcin; Gercekcioglu, Hamza; Baykal, YahyaMultimode field correlations are evaluated in atmospheric turbulence. High order field correlations are special cases of the results that we obtained in this paper. Field correlations are presented for various numbers of mul- timodes, various multimode contents of the same number of modes, and various high order modes versus the diagonal distance from various receiver points, source size, link length, structure constant, and the wavelength. Our results will be of help especially in the design of heterodyne systems operating in turbulent atmosphere and fiber coupling efficiency in systems employing multimode excitation.(c) 2023 Optica Publishing GroupArticle 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: 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 America