Elektrik Elektronik Mühendisliği Bölümü

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Citation Count: Gökçe, M.C., Baykal, Y.K. (2018). Aperture averaging and BER for Gaussian beam in underwater oceanic turbulence. Optic Communications, 410, 830-835. http://dx.doi.org/10.1016/j.optcom.2017.11.049
Aperture averaging and BER for Gaussian beam in underwater oceanic turbulence
(Elsevier Science BV, 2018) Gökçe, Muhsin Caner; Baykal, Yahya; 28643; 7812
In an underwater wireless optical communication (UWOC) link, power fluctuations over finite-sized collecting lens are investigated for a horizontally propagating Gaussian beam wave. The power scintillation index, also known as the irradiance flux variance, for the received irradiance is evaluated in weak oceanic turbulence by using the Rytov method. This lets us further quantify the associated performance indicators, namely, the aperture averaging factor and the average bit-error rate (). The effects on the UWOC link performance of the oceanic turbulence parameters, i.e., the rate of dissipation of kinetic energy per unit mass of fluid, the rate of dissipation of mean-squared temperature, Kolmogorov microscale, the ratio of temperature to salinity contributions to the refractive index spectrum as well as system parameters, i.e., the receiver aperture diameter, Gaussian source size, laser wavelength and the link distance are investigated.
Citation Count: Gökçe, M.C., Baykal, Y., Uysal, M. (2016). Aperture averaging in multiple-input single-output free-space optical systems. Journal Of The Optical Society Of America A-Optics İmage Science And Vision, 33(6), 1041-1048. http://dx.doi.org/10.1364/JOSAA.33.001041
Aperture averaging in multiple-input single-output free-space optical systems
(Optical Soc Amer, 2016) Gökçe, Muhsin Caner; Baykal, Yahya; Uysal, Murat; 28643; 7812; 124615
Multiple-input single-output (MISO) techniques are employed in free-space optical (FSO) links to mitigate the degrading effects of atmospheric turbulence. In this paper, for the MISO FSO system, a partially coherent radial array and a finite-sized receiver aperture are used at the transmitter and the receiver, respectively. Using the extended Huygens - Fresnel principle, we formulate the average power and the power correlation at the finite-sized slow detector in weak atmospheric turbulence. System performance indicators such as the power scintillation index and the aperture averaging factor are determined. Effects of the source size, ring radius, receiver aperture radius, link distance, and structure constant and the degree of source coherence are analyzed on the performance of the MISO FSO system. In the limiting cases, the numerical results are found to be the same when compared to the existing coherent and partially coherent Gaussian beam scintillation indices.
Citation Count: Gökçe, M.C...et al. (2015). Aperture averaging in multiple-input single-output free-space optical systems. Optical Engineering, 54(6). http://dx.doi.org/10.1117/1.OE.54.6.066103
Aperture averaging in multiple-input single-output free-space optical systems
(Spie-Soc Photo-Optical Instrumentation Engineers, 2015) Gökçe, Muhsin Caner; Baykal, Yahya; Kamacıoğlu, 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.
Citation Count: Gökçe, M.C., Baykal, y. (2018). Aperture averaging in strong oceanic turbulence. Optics Communications, 413, 196-199. http://dx.doi.org/ 10.1016/j.optcom.2017.12.059
Aperture averaging in strong oceanic turbulence
(Elsevier Science BV, 2018) Gökçe, Muhsin Caner; Baykal, Yahya; 28643; 7812
Receiver aperture averaging technique is employed in underwater wireless optical communication (UWOC) systems to mitigate the effects of oceanic turbulence, thus to improve the system performance. The irradiance flux variance is a measure of the intensity fluctuations on a lens of the receiver aperture. Using the modified Rytov theory which uses the small-scale and large-scale spatial filters, and our previously presented expression that shows the atmospheric structure constant in terms of oceanic turbulence parameters, we evaluate the irradiance flux variance and the aperture averaging factor of a spherical wave in strong oceanic turbulence. Irradiance flux variance variations are examined versus the oceanic turbulence parameters and the receiver aperture diameter are examined in strong oceanic turbulence. Also, the effect of the receiver aperture diameter on the aperture averaging factor is presented in strong oceanic turbulence.
Citation Count: Gökçe, M.C., Baykal, Y., Uysal, M. (2016). Bit error rate analysis of MISO FSO systems. Waves In Random And Complex Media, 26(4), 642-649. http://dx.doi.org/10.1080/17455030.2016.1183836
Bit error rate analysis of MISO FSO systems
(Taylor&Francis Ltd., 2016) Gökçe, Muhsin Caner; Baykal, Yahya; Uysal, Murat; 28643; 7812; 124615
Multiple-input single-output (MISO) systems are employed in free space optical (FSO) links to mitigate the degrading effects of atmospheric turbulence. In this paper, we consider a MISO FSO system with practical transmitter and receiver configuration that consists of radial laser array with Gaussian beams and a Gaussian receiver aperture function. We have employed our previously derived formulation of the power scintillation in which Huygens-Fresnel principle was employed. Therefore, we choose system parameters within the range of validity of the wave structure functions. Using the on-off keying modulation and the log-normal probability distribution function, we quantify the average bit error rate (< BER >) of laser array beams in weak turbulence. It is observed that the radial array beams at the transmitter are more advantageous than the single Gaussian beam. However, increasing the number of array beamlets to more than three seems to have negligible effects on < BER >. It is further observed that < BER > decreases when the source size, the ring radius and the receiver aperture radius increase.
Citation Count: Ata, Yalcin; Baykal, Yahya; Gokce, Muhsin Caner, "Error performance of optical wireless communication systems exercising BPSK subcarrier intensity modulation in non-Kolmogorov turbulent atmosphere", Optics Communications, Vol. 436, pp. 108-112, (2019).
Error performance of optical wireless communication systems exercising BPSK subcarrier intensity modulation in non-Kolmogorov turbulent atmosphere
(Elsevier Science BV, 2019) Ata, Yalçın; Baykal, Yahya; Gökçe, Muhsin Caner; 7812; 28643
Subcarrier intensity modulation (SIM) scheme is preferred due to efficient bandwidth usage superiority over other modulation techniques such as on-off keying (OOK), pulse position modulation (PPM). In this paper, we investigate the bit error rate (BER) performance of optical wireless communication (OWC) system using binary phase shift keying (BPSK) SIM in non-Kolmogorov turbulent atmosphere. We pay attention to the weak turbulence conditions by using Rytov approximation and considering that the receiver is a PIN photodetector. Propagating beam type is Gaussian. It is seen that BER performance of the BPSK SIM OWC is significantly affected from non-Kolmogorov power law exponent, load resistor, responsivity of the PIN photodetector, bandwidth, beam source size, turbulence strength and noise factor.
Citation Count: Ata, Y., Baykal, Y., Gökçe, M.C. (2018). M-ary pulse position modulation performance in non-Kolmogorov turbulent atmosphere. Applied Optics, 57(24), 7006-7011. http://dx.doi.org/ 10.1364/AO.57.007006
M-ary pulse position modulation performance in non-Kolmogorov turbulent atmosphere
(Optical Soc Amer, 2018) Ata, Yalçın; Baykal, Yahya; Gökçe, Muhsin Caner; 7812; 28643
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
Citation Count: Gökçe, M.C., Baykal, Y., Ata, Y. (2018). Performance analysis of M-ary pulse position modulation in strong oceanic turbulence. Optics Communications, 427, 573-577. http://dx.doi.org/10.1016/j.optcom.2018.07.037
Performance analysis of M-ary pulse position modulation in strong oceanic turbulence
(Elsevier Science Bv, 2018) Gökçe, Muhsin Caner; Baykal, Yahya; Ata, Yalçın; 28643; 7812
In this paper, we consider an underwater wireless optical communication (UWOC) system which consists of an M-ary pulse position modulated (PPM) Gaussian optical beam at the transmitter and an avalanche photodiode (APD) at the receiver. In strong oceanic turbulence, we aimed at investigating the system performance in terms of bit error rate (BER) by the help of gamma-gamma channel model. For this purpose, the average power and the aperture averaged scintillation at the finite sized detector are derived by using the extended Huygens-Fresnel principle and the asymptotic Rytov theory, respectively. BER variations are examined versus the average APD gain, modulation order, bit rate as well as the oceanic turbulence parameters, i.e., the rate of dissipation of kinetic energy per unit mass of fluid, the rate of dissipation of mean-squared temperature and the ratio of temperature to salinity contributions to the refractive index spectrum.
Citation Count: Gökçe, M.C., Baykal, Y., Uysal, M. (2016). Performance analysis of multiple-input multiple-output free-space optical systems with partially coherent Gaussian beams and finite-sized detectors. Optical Engineering, 55(11). http://dx.doi.org/10.1117/1.OE.55.11.111607
Performance analysis of multiple-input multiple-output free-space optical systems with partially coherent Gaussian beams and finite-sized detectors
(Spie-Soc Photo-Optical Instrumentation Engineers, 2016) Gökçe, Muhsin Caner; Baykal, Yahya; Uysal, Murat; 28643; 7812; 124615
Multiple-input multiple-output (MIMO) techniques are employed in free-space optical (FSO) links to mitigate the degrading effects of atmospheric turbulence. We consider a MIMO FSO system, which consists of a radial laser array with partially coherent Gaussian beams at the transmitter and a detector array with Gaussian apertures at the receiver. The average power and the power correlation function at the finite-sized receiver apertures are formulated by using the extended Huygens-Fresnel principle in weak atmospheric turbulence. This let us further quantify the performance metrics such as the power scintillation index, the aperture averaging factor, and the average bit error rate (BER) as functions of system parameters. The derived power scintillation equation correctly reduces to the existing coherent and partially coherent Gaussian beam scintillation indices in the limiting cases. Using the performance metrics, we analyze the effect of various practical system parameters on the performance of a MIMO FSO system. Practical system parameters include the transmitter and receiver ring radius, number of beamlets, number of finite-aperture receivers, source size, degree of source coherence, receiver aperture radius, link distance, and the structure constant of atmosphere.
Citation Count: Gökçe, M.C., Baykal, Y. (2016). Scintillation analysis of multiple-input single-output underwater optical links. Applied Optics, 55(22), 6130-3136. http://dx.doi.org/10.1364/AO.55.006130
Scintillation analysis of multiple-input single-output underwater optical links
(Optical Soc Amer, 2016) Gökçe, Muhsin Caner; Baykal, Yahya; 28643; 7812
Multiple-input single-output (MISO) techniques are employed in underwater wireless optical communication (UWOC) links to mitigate the degrading effects of oceanic turbulence. In this paper, we consider a MISO UWOC system which consists of a laser beam array as transmitter and a point detector as receiver. Our aim is to find the scintillation index at the detector in order to quantify the system performance. For this purpose, the average intensity and the average of the square of the intensity are derived in underwater turbulence by using the extended Huygens-Fresnel principle. The scintillation index and the average bit-error-rate (< BER >) formulas presented in this paper depend on the oceanic turbulence parameters, such as the rate of dissipation of the mean-squared temperature, rate of dissipation of kinetic energy per unit mass of fluid, Kolmogorov microscale, and the ratio of temperature to salinity contributions to the refractive index spectrum, the link length, and the wavelength. Recently, we have derived an equivalent structure constant of atmospheric turbulence and expressed it in terms of the oceanic turbulence parameters [Appl. Opt. 55, 1228 (2016)]. In the formulation in this paper, this equivalent structure constant is utilized, which enables us to employ the existing similar formulation valid in atmospheric turbulence.
Citation Count: Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin C., "Structure parameter of anisotropic atmospheric turbulence expressed in terms of anisotropic factors and oceanic turbulence parameters", Applied Optics, Vol. 58, No. 2, pp. 454-460, (2019).
Structure parameter of anisotropic atmospheric turbulence expressed in terms of anisotropic factors and oceanic turbulence parameters
(Optical Soc Amer, 2019) Baykal, Yahya; Ata, Yalçın; Gökçe, Muhsin Caner; 7812; 28643
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

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