Bayraktar, Mert
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Arş. Gör.
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Elektronik ve Haberleşme Mühendisliği
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Scholarly Output
7
Articles
10
Citation Count
45
Supervised Theses
2
7 results
Scholarly Output Search Results
Now showing 1 - 7 of 7
Article Citation - WoS: 20SNR bounds of FSO links and its evaluation for selected beams(Taylor & Francis Ltd, 2015) Eyyuboglu, Halil T.; Bayraktar, Mert; Bayraktar, Mert; 7688; 53038; Elektronik ve Haberleşme MühendisliğiWe formulate the signal-to-noise ratio (SNR) for free-space optical links. Upon inserting typical operating parameters, it is seen that SNR well approximates to the inverse of aperture averaged scintillation parameter. By adopting a common source beam power of 10 mW, we select three different source sizes of Gaussian, annular Gaussian (AG), and cosh-Gaussian beams. We then evaluate the SNR of these beams. Our results indicate that when fixed aperture opening is used, fully and partially coherent beams yield almost the same SNR performance. On the other hand, however, focusing and lowering wavelength of operation appear to be quite instrumental in improving the SNR performance. In this context, medium-sized AGB seems to exhibit the best performance.Article Citation - WoS: 8Citation - Scopus: 8Cylindrical-sinc beam(Elsevier Gmbh, Urban & Fischer verlag, 2014) Bayraktar, Mert; Bayraktar, Mert; Basdemir, H. Deniz; Başdemir, Hüsnü Deniz; 53038; 20399; Elektronik ve Haberleşme MühendisliğiPropagation of diffracted beams in free space has already been identified. One possible solution is derived from the Helmholtz wave equation and this solution is named as cylindrical-sinc beam. Therefore, cylindrical-sinc beam is a new beam type which can be obtained from Helmholtz equation. Diffraction properties of this new beam type were observed from an opaque aperture screen. Additionally, geometrical theory of diffraction is used to determine numerical values of diffracted fields. This new beam type which does not exist in the literature was observed by using these methods passing through an opaque aperture. The obtained expression was analyzed numerically. Simulation results of the beam depending on the length of aperture and distance to the observation point were added. (C) 2014 Elsevier GmbH. All rights reserved.Master Thesis Comparison of probability of error performance for truncated Bessel and Bessel Gauss beams(2015) Bayraktar, Mert; Elektronik ve Haberleşme MühendisliğiIn this thesis, probability of error and SNR performances of truncated Bessel and Bessel-Gauss beams in free space optical communication system were compared. Source beams were determined as truncated Bessel and Bessel-Gauss beam. Then, the simulation of propagation of these beams was simulated in MATLAB. This simulation was performed by using random phase screen approach. Random phase screen was used as a model of the turbulent atmosphere in reality. Data symbols were transmitted to receiver side through the random phase screen. To reach the probability of error of this communication system, error counting was applied. By this way, performance comparison of the beams was derived and relative plots were located in this paper.Article Citation - WoS: 13Citation - Scopus: 13Propagation properties of optical bottle beam in turbulence(Spie-soc Photo-optical instrumentation Engineers, 2019) Bayraktar, Mert; Bayraktar, Mert; Eyyuboglu, Halil Tanyer; 53038; Elektronik ve Haberleşme MühendisliğiWe study the propagation properties of optical bottle beams in turbulent atmosphere. By allowing the mathematical expression of source plane to cover both the symmetric and asymmetric forms, the beam is propagated through turbulence using random phase screens. On the source plane, the intensity profile of the bottle beam resembles a dark hollow beam with an outside ring for symmetric cases, whereas it becomes divided into two or more separate lobes for the asymmetric cases. During propagation, both symmetric and asymmetric beams concentrate the intensity toward the center, eventually assuming a Gaussian shape, where this process seems to be more rapid for the former beam types. The rising trend of the kurtosis parameter of bottle beams changes to a falling trend when the refractive index structure constant is reduced from 10(-14) to 10(-13) m(-2/3). (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)Doctoral Thesis Scintillation and bit error rate performance comparison of bottle and sine hollow beams(2019) Bayraktar, Mert; Elektronik ve Haberleşme MühendisliğiBu çalışma kaynak düzleminde şişe ve sinus oyuk ışınları kullanan kablosuz optik haberleşme hatlarında parıldama davranışı ve hata olasılığı tahminini içermektedir. Haberleşme linki üzerindeki performasına ek olarak, şişe ışınının yayılma ve kurtosis parametresi de analiz edilmiştir. Şişe ışının parıldamasının analitik türetimi Rytov parıldama teorisinden faydalanarak yapılmıştır. Denklemler çözülmesi çok zor olduğundan yayılma özellikleri, kurtosis parametresi, parıldama tahmini ve hata olasılığı değerleri rastgele faz tabakaları yöntemi kullanılarak elde edilmiştir. Aynı merthodu kullanara sinus oyuk ışınının da parıldama ve bit hata oranı hesaplanmıştır. Sonuçlarımız gösteriyor ki, asimetrik şişe ışınlarının parıldaması aynı şartlarda karşılık gelen simetrik ışınlara nazaran daha azdır. Bu da bize asimetrik ışınların sabit sinyal gürültü oranında daha düşük bit hata oranına sahip olduğunu sonucunu getirmektedir. Zayıf türbülansta sinüs oyuk ışınının parıldaması Gaussian ışınından daha az olduğu için, bu ışın zayıf türbülansta bit hata oranı bakımından daha vantajlı görünmektedir. Parıldama sonuçları küresel dalga ile karşılaştırılmış ve elde edilen hata olasılığı değerleri analitik formül ile kaşılaştırılıp bu çalışmada çizilmiştir.Article Citation - WoS: 12Citation - Scopus: 13Propagation properties of cylindrical sinc Gaussian beam(Taylor & Francis Ltd, 2016) Eyyuboglu, Halil T.; Bayraktar, Mert; Bayraktar, Mert; 42699; 53038; Elektronik ve Haberleşme MühendisliğiWe investigate the propagation properties of cylindrical sinc Gaussian beam in turbulent atmosphere. Since an analytic solution is hardly derivable, the study is carried out with the aid of random phase screens. Evolutions of the beam intensity profile, beam size and kurtosis parameter are analysed. It is found that on the source plane, cylindrical sinc Gaussian beam has a dark hollow appearance, where the side lobes also start to emerge with increase in width parameter and Gaussian source size. During propagation, beams with small width and Gaussian source size exhibit off-axis behaviour, losing the dark hollow shape, accumulating the intensity asymmetrically on one side, whereas those with large width and Gaussian source size retain dark hollow appearance even at long propagation distances. It is seen that the beams with large widths expand more in beam size than the ones with small widths. The structure constant values chosen do not seem to alter this situation. The kurtosis parameters of the beams having small widths are seen to be larger than the ones with the small widths. Again the choice of the structure constant does not change this trend.Article Citation - WoS: 12Citation - Scopus: 11Estimation of scintillation and bit error rate performance of sine hollow beam via random phase screen(Elsevier Gmbh, 2019) Bayraktar, Mert; Bayraktar, Mert; 53038; Elektronik ve Haberleşme MühendisliğiWe study scintillation and bit error rate performance of sine hollow beam in turbulent atmosphere. Since source field expression involves higher order term, we model atmosphere utilizing random phase screen. We show that normal sine hollow beam (a = b) having higher order has the least scintillation index considering point like scintillation. This brings us bit error rate(BER) of this type of beam in turbulent atmosphere is less comparing with Gauss beam when we use point like receiver. BER of anomalous beam (a not equal b) having less scintillation index is lower than Gauss beam in strong turbulence region. In terms of aperture averaged scintillation, first order normal sine hollow beam and anomalous beams have less scintillation than Gauss beam.
