WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653
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Conference Object Citation - WoS: 1Citation - Scopus: 1Off-Axis Field Correlations in Turbulence(Ieee, 2013) Baykal, Yahya Kemal; Baykal, Yahya; Elektrik-Elektronik MühendisliğiThe 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 Citation - WoS: 5Citation - Scopus: 6Propagation of Optical Flat-Topped Gaussian Beams in Satellite Links(Ieee, 2009) Kamacioglu, Canan; Arpali, Serap A.; Baykal, Yahya; Yazgan, ErdemPropagation of optical flat-topped Gaussian beams in earth-satellite optical communication links is investigated where part of the link is turbulent atmosphere. Flat-topped Gaussian source field is obtained by superposing many Gaussian beams of different source size. Starting with the flat-topped Gaussian incidence at the earth surface, the average intensity at the satellite is formulated by using the extended Huygens Fresnel principle. For the structure constant variation versus height, Hufnagel-Valley model is employed in the vertical and slant paths. The received average intensity is numerically calculated and the effects of the source and medium parameters on the received average intensity profile are examined for different zenith angles. In earth-satellite optical communications links, the advantages of using flat-topped Gaussian beams as compared to Gaussian beams are scrutinized.Conference Object Citation - Scopus: 1Laser Array Beam Scintillation in Oceanic Turbulence(Ieee, 2020) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin C.In this study, on-axis scintillation of laser array beam in oceanic turbulent medium is investigated. By using Rytov method, scintillation index variations are reported in connection with the propagation distance, rate of dissipation of turbulent kinetic energy, microscale length, rate of dissipation of the mean squared temperature, salinity ratio, radius of the ring of beamlets which compose the beam array, source size and number of beamlets. Results show that turbulence effect on the laser beam increases with the propagation distance, microscale length, rate of dissipation of the mean squared temperature, salinity ratio, array radius, source size and number of beamlets but decreases when rate of dissipation of turbulent kinetic energy increases.Conference Object Citation - WoS: 2Citation - Scopus: 3Ber for Higher Order Laser Modes in Optical Wireless Underwater Communications(Ieee, 2016) Arpali, Serap Altay; Baykal, Yahya; Arpali, CaglarAverage bit error rate (<BER>) of an underwater optical communication system is analyzed for higher order laser beams. For this purpose, the effects of oceanic turbulence parameters and link parameters on single mode higher order laser beams are investigated.Conference Object Citation - Scopus: 2Effect of Partial Coherence on Miso Fso Systems(Ieee, 2015) Baykal, Yahya; Uysal, Murat; Gokce, Muhsin CanerMultiple-input single-output (MISO) techniques are employed in free space optical (FSO) systems to mitigate the degrading effects of atmospheric turbulence and therefore the link reliability is improved. In this paper, we consider an incoherent radial array beams and a finite sized slow detector for MISO FSO systems. We have derived the average power and power correlation formulas on the finite sized slow detector using the Huygens Fresnel principle in weak atmospheric turbulence. This helps us to find the system performance, such as power scintillation and aperture averaging factor. Effect of system parameters such as the source size, the ring radius, the degree of coherence, the link distance, the structure constant and the receiver aperture radius are analyzed on the performance of MISO FSO systems.Conference Object Citation - WoS: 4Citation - Scopus: 11Effects of Focused and Collimated Laser Beams on the Performance of Underwater Wireless Optical Communication Links(Ieee, 2015) Catmakas, Omer Kemal; Genc, Fatih; Baykal, Yahya; Arpali, Serap Altay; Arpali, Caglar; Keskin, AysanIn this paper, the optical transmittance and bit error rate (BER) of focused and collimated laser beams are experimentally examined in an underwater optical wireless communication link with different water types. The water types used are fresh water, salty water and their variations with maalox in order to obtain turbid water. In bit error rate (BER) analysis, on-off keying (OOK) is used together with Bose-Chaudhuri-Hocquenghem (BCH) and convolutional codes. Results show that salt and maalox content decreases the transmittance, the convolution codes have better BER performance than BCH codes under the same modulation scheme (i.e., OOK) and focusing improves both the transmittance and BER performance as compared to collimated beams.