Browsing by Author "Gokce, Muhsin C."

Now showing 1 - 15 of 15

Citation - WoS: 7
Citation - Scopus: 8
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; Gokce, Muhsin C.; Ata, Yalcin; 7812; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
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.
Citation - WoS: 8
Citation - Scopus: 9
Aperture averaging in multiple-input single-output free-space optical systems
(Spie-soc Photo-optical instrumentation Engineers, 2015) Gokce, Muhsin C.; Baykal, Yahya; Kamacioglu, Canan; Uysal, Murat; 28643; 7812; 124615; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
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)
Citation - WoS: 6
Citation - Scopus: 10
Application of adaptive optics on bit error rate of M-ary pulse-position-modulated oceanic optical wireless communication systems
(Iop Publishing Ltd, 2020) Baykal, Yahya; Gokce, Muhsin C.; Ata, Yalcin; 7812; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
An adaptive optics correction arising from the sum of tilt, focus, astigmatism and coma components is applied to the bit error rate (BER) of M-ary pulse-position-modulated (PPM) oceanic optical wireless communication systems. The percentage reduction in BER is evaluated versus the oceanic turbulence parameters of the ratio of temperature to salinity contributions to the refractive index spectrum, the rate of dissipation of mean-squared temperature and that of kinetic energy per unit mass of fluid under different data bit rates, avalanche photodiode (APD) average current gains and the M values of the M-ary PPM. Our findings indicate that the percentage reduction in BER becomes larger when the ratio of temperature to salinity contributions to the refractive index spectrum or the rate of dissipation of mean-squared temperature or the data bit rate or the M value of the M-ary PPM is smaller, and when the rate of dissipation of kinetic energy per unit mass of fluid or the APD average current gain is larger.
Citation - WoS: 2
Citation - Scopus: 2
Ber anaylsis for super lorentz-gaussian laser beamspropagating in turbulent media
(Gazi Univ, Fac Engineering Architecture, 2013) Gokce, Muhsin C.; Sari, Filiz; Ozek, Faruk; 28643; Elektronik ve Haberleşme Mühendisliği
In this work, BER-SNR variation of super Lorentz-Gaussian laser beam that propagating horizontally path in turbulent media is analyzed. Using scintillation index which is obtained by extented Huygens-Fresnel principle, BER - SNR value is calculated. Matlab program is used to show BER - SNR variation depending on link distance and beamwidth. To conclude, in short link range, super Lorentz-Gaussian beam is proven to be better link performance superior to commercially available Gaussian beam.
Citation - WoS: 9
Citation - Scopus: 11
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; Baykal, Yahya; Gokce, Muhsin C.; 7812; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
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
Citation - WoS: 0
Citation - Scopus: 1
Field Correlations of Multimode Optical Beams in Underwater Turbulence
(Optica Publishing Group, 2024) Baykal, Yahya; Gokce, Muhsin C.; Ata, Yalcin; Gercekcioglu, Hamza; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
For multimode optical beams, field correlations at the receiver plane are found in underwater turbulence. Field correlations of single high order beams in underwater turbulence are special cases of our formulation. Variations of field correlations against the underwater turbulence parameters and the diagonal length from various receiver points are examined for different multimode and single high order beams. Stronger underwater turbulence is found to reduce the field correlations of multimode and single high order optical beams. The results will be of help in heterodyne detection analysis and fiber coupling efficiency in an underwater medium experiencing turbulence. (c) 2024 Optica Publishing Group
Citation - WoS: 3
Citation - Scopus: 5
Irradiance fluctuations of partially coherent super Lorentz Gaussian beams
(Elsevier, 2011) Gokce, Muhsin C.; Eyyuboglu, Halil T.; 7688; 28643; Elektronik ve Haberleşme Mühendisliği
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.
Citation - WoS: 0
Citation - Scopus: 1
Laser array beam scintillation in oceanic turbulence
(Ieee, 2020) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin C.; 7812; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
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.
Citation - WoS: 4
Citation - Scopus: 3
Laser array field correlations in underwater turbulence
(Taylor & Francis Ltd, 2022) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin C.; 7812; Elektrik-Elektronik Mühendisliği; Elektronik ve Haberleşme Mühendisliği
In underwater turbulent medium, field correlations are found when the incidence is a laser beam array. Variations of the field correlations against the variations in the ring radius of laser array beam, number of beamlets composing the laser array, source size, underwater turbulence parameters, i.e. the ratio of temperature to salinity contributions to the refractive index spectrum, rate of dissipation of mean-squared temperature and rate of dissipation of kinetic energy per unit mass of fluid, are investigated. Field correlations of laser arrays are found to be larger than the field correlations of the single beams. The effect of underwater turbulence is to reduce the field correlation of laser arrays.
Citation - WoS: 24
Citation - Scopus: 26
M-ary pulse position modulation performance in non-Kolmogorov turbulent atmosphere
(Optical Soc Amer, 2018) Ata, Yalcin; Baykal, Yahya; Gokce, Muhsin C.; 7812; 28643; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
The 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 America
Citation - WoS: 8
Citation - Scopus: 8
M-ary pulse position modulation performance with adaptive optics corrections in atmospheric turbulence
(Taylor & Francis Ltd, 2020) Ata, Yalcin; Gokce, Muhsin C.; Baykal, Yahya; 7812; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
The performance of M-ary pulse position modulated (PPM) optical wireless communication (OWC) systems in atmospheric weak turbulence medium is evaluated by using adaptive optics corrections. Piston, tilt, defocus and coma components of adaptive optics corrections are applied to the avalanche photodetector (APD) type of receiver and the results are obtained depending on various turbulence and receiver parameters. The lognormal channel distribution is used to model the weak atmospheric turbulence conditions. Adaptive optics correction increases the bit-error-rate (BER) performance of an OWC system operating in atmospheric turbulence conditions. Piston component yields the highest BER performance, followed by the tilt, defocus and coma adaptive optics correction components respectively.
Citation - WoS: 5
Citation - Scopus: 7
Performance analysis of mimo fso systems with radial arraybeams and finite sized detectors
(Spie-int Soc Optical Engineering, 2014) Gokce, Muhsin C.; Kamacioglu, Canan; Uysal, Murat; Baykal, Yahya; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
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.
Citation - WoS: 3
Citation - Scopus: 4
Performance 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.; 7812; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
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 America
Citation - WoS: 8
Citation - Scopus: 8
Structure parameter of anisotropic atmospheric turbulence expressed in terms of anisotropic factors and oceanic turbulence parameters
(Optical Soc Amer, 2019) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin C.; 7812; 28643; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
The 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 America
Citation - WoS: 58
Citation - Scopus: 72
Underwater turbulence, its effects on optical wireless communication and imaging: A review
(Elsevier Sci Ltd, 2022) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin C.; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği
Theory of optical turbulence in underwater medium and the effects of underwater turbulence on various ap-plications done in underwater or under ocean are reviewed. A detailed survey of underwater turbulence studies in literature is reported. Underwater physics covering salinity, temperature and dissipation rates, various power spectra such as Hill, Nikishov and Nikishov, Li, new form and the oceanic turbulence optical power spectrum (OTOPS) spectra are explained. Wave and phase structure functions, related coherence length, anisotropy, in-tensity, field correlations in underwater turbulence are elaborated. Scintillation indices of spherical, plane, Gaussian, and other types of optical beams are mentioned. Bit-error-rate (BER), signal-to-noise-ratio (SNR) performances of optical wireless communication systems operating in underwater, and the effects of modulation types of these systems on the performances are reported. Channel capacity of underwater optical wireless communication systems when the channel experiences log-normal, gamma-gamma, Weibull, and negative exponential statistics are reflected. Underwater imaging and the related modulation transfer function, under-water turbulence mitigation techniques in the form of aperture averaging, adaptive optics, receiver, transmitter and multiple-input, multiple-output (MIMO) spatial diversity techniques are revised.