Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/411
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Conference Object Citation - Scopus: 1Intensity Fluctuations of Incoherently Superposed Gaussian Beams in Atmospheric Turbulence(Spie-int Soc Optical Engineering, 2010) Baykal, YahyaIntensity fluctuations of incoherently superposed Gaussian beams are formulated in weak turbulence by employing the extended Huygens-Fresnel principle. Each individual beam superposed is taken to be fully incoherent. The scintillation index evaluated for different number of beams indicates that as the number of beams increase, scintillations decrease. Incoherent superposition of smaller sized Gaussian sources exhibits smaller fluctuations. Comparing the scintillation index arising from incoherently superposed Gaussian beams to the scintillation index of coherently superposed Gaussian beams of the same structure shows that incoherent superposition yields lower intensity fluctuations, thus can be advantageous in atmospheric optical communication links.Conference Object Citation - WoS: 1Citation - Scopus: 1Effects of Laser Multimode Content on the Angle-Of Fluctuations in Free Space Optics Access Systems(Spie-int Soc Optical Engineering, 2004) Eyyuboglu, HT; Baykal, YThe effects of the multimode content in a laser beam on the angle-of-arrival fluctuations are examined for free space optics (FSO) access systems. Multimode excitation is represented by coherent addition of Hermite-Gaussian higher order modes. Root mean square angle-of-arrival fluctuations are formulated using the previously reported multimode phase structure function, which is valid in weak atmospheric turbulence. Results are found for practical FSO links operating at 1550 nm and 850 nm wavelengths and for link spans of up to 5 km. In choosing the mode content, various sequential grouping of all possible mode combinations are used up to a certain order (n,m) mode. We start with the single fundamental mode (TEM00) and span up to the highest order (n = 10, m = 10) mode. In this manner, different degrees of source coherence are also taken into account. Angle-of-arrival fluctuations are found to be in the range of several tens of muradians and almost insensitive to the mode content except for the cases when the mode group terminates with an odd mode. In such instances, the fluctuations rise to a few hundreds of murad. Comparing our results with the field of view of a practical FSO receiver, which is several mrad, we conclude that the-angle-of arrival fluctuations due to multimode excitation will not influence the FSO link performance to a major extent.Book Part Citation - WoS: 3Optical Propagation in Unguided Media(Springer-verlag Berlin, 2016) Baykal, Yahya KemalThis chapter provides fundamentals of light propagation in unguided media and particularly discusses turbulence of transmission environment. The degradation effects of turbulence in the received signal of an OWC system are presented. The turbulence power spectra used in the formulation of various entities are given in various links operating in different environments such as atmosphere, space and underwater. The Rytov method and the extended Huygens-Fresnel principle are employed in the evaluation of the average intensity and the scintillation index. Effects of different optical beam profiles in the average received intensity and the scintillation index are further examined. Finally, some mitigation methods, such as the transmitter and the receiver aperture averaging, to reduce the turbulence degradation are given.Conference Object Influence of Atmospheric Turbulence on Quality of Multichannel Laser Radiation and Correction for Distortion(Spie-int Soc Optical Engineering, 2016) Kanev, F. Yu.; Lukin, V. P.; Makenova, N. A.; Antipov, O. L.; Eyyuboglu, Halil TanyerIn this paper the results of simulation are presented of multichannel radiation propagation in the atmosphere, and correction for turbulent distortion on the base of the beam phase control is considered. The results demonstrate dependence of correction effectiveness on number of channels and on precision of a reference beam phase reconstruction. Additionally increase of effectiveness is possible with adjustment of amplification in the channels of the optical system, i.e., with the use of amplitude-phase control of radiation.