Browsing by Author "Gokce, Muhsin C."

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Anisotropy effect on performance of subcarrier intensity modulated binary phase shift keying optical wireless communication links in weakly turbulent underwater channel
(Taylor & Francis Ltd, 2019) Baykal, Yahya; Gökçe, Muhsin Caner; Gokce, Muhsin C.; Ata, Yalcin; 7812
The effect of the anisotropy on the bit-error-rate (BER) performance of subcarrier intensity modulated (SIM) binary phase shift keying (BPSK) optical wireless communication (OWC) links operating in weakly turbulent underwater channels is examined. BER variations versus the anisotropic factor are examined when the bandwidth, photodetector responsivity, load resistor and the underwater turbulence parameters are varied. As anisotropy in the underwater channel becomes larger, SIM BPSK OWC links have better BER performance at any link and turbulence parameter.
Aperture averaging in multiple-input single-output free-space optical systems
(Spie-soc Photo-optical instrumentation Engineers, 2015) Gokce, Muhsin C.; Gökçe, Muhsin Caner; Baykal, Yahya; Kamacioglu, Canan; Uysal, Murat; 28643; 7812; 124615
Multiple-input single-output systems are employed in free-space optical links to mitigate the degrading effects of atmospheric turbulence. We formulate the power scintillation as a function of transmitter and receiver coordinates in the presence of weak atmospheric turbulence by using the extended Huygens Fresnel principle. Then the effect of the receiver aperture averaging is quantified. To get consistent results, parameters are chosen within the range of validity of the wave structure functions. Radial array beams and a Gaussian weighting aperture function are used at the transmitter and the receiver, respectively. It is observed that the power scintillation decreases when the source size, the ring radius, the receiver aperture radius, and the number of array beamlet increase. However, increasing the number of array beamlets to more than three seems to have negligible effect on the power scintillation. It is further observed that the aperture averaging effect is stronger when radial array beams are employed instead of a single Gaussian beam. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Effect of strong atmospheric non-Kolmogorov turbulence on the M-ary PSK subcarrier intensity modulated free space optical communications system performance
(Optical Soc Amer, 2019) Ata, Yalcin; Gökçe, Muhsin Caner; Baykal, Yahya; Gokce, Muhsin C.; 7812
Atmospheric 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 America
Irradiance fluctuations of partially coherent super Lorentz Gaussian beams
(Elsevier, 2011) Gokce, Muhsin C.; Gökçe, Muhsin Caner; Eyyuboglu, Halil T.; 7688; 28643
By using the semi-analytic approach introduced earlier, we formulate and subsequently evaluate the irradiance fluctuations of partially coherent super Lorentz Gaussian beams for orders of 10 and 11. Within the range of examined source and propagation conditions, our calculations show that there will be less fluctuations at short propagation distances as the Lorentzian property is increased. But the reverse will be applicable, if the longer propagation distances are considered. The use of focusing will cause reductions, particularly for beams with increased Lorentzian property. (C) 2011 Elsevier B.V. All rights reserved.
Performance analysis of mimo fso systems with radial arraybeams and finite sized detectors
(Spie-int Soc Optical Engineering, 2014) Gokce, Muhsin C.; Gökçe, Muhsin Caner; Kamacioglu, Canan; Uysal, Murat; Baykal, Yahya
Multiple-input multiple-output (MIMO) systems are employed in free space optical (FSO) links to mitigate the degrading effects of atmospheric turbulence. In this paper, we consider a MIMO FSO system with practical transmitter and receiver configurations that consists of a radial laser array with Gaussian beams and finite sized detectors. We formulate the average received intensity and the power scinitillation as a function of the receiver coordinates in the presence of weak atmospheric turbulence by using the extended Huygens-Fresnel principle. Then, integrations over the finite sized multiple detectors are performed and the effect of the receiver aperture averaging is quantified. We further derive an outage probability expression of this MIMO system in the presence of turbulence-induced fading channels. Using the derived expressions, we demonstrate the effect of several practical system parameters such as the ring radius, the number of array beamlets, the source size, the link length, structure constant and the receiver aperture radius on the system performance.