Browsing by Author "Altuncu, Ahmet"

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Comparative analysis of the effect of optical fiber spin profiles on polarization mode dispersion
(IEEE, 2015-01-01) Sadık, Şerif Ali; Başgümüş, Arif; Durak, Fırat Ertaç; Karlık, Sait Eser; Altuncu, Ahmet; KARLIK, SAİT ESER; Uluda Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.; AAJ-2404-2021
In long-haul and high-bit-rate optical fiber transmission systems Polarization Mode Dispersion (PMD) is one of the main reasons for pulse broadening. In order to reduce PMD-based problems, current studies rely on novel PMD compensators and low-PMD fiber productions. In this paper, after describing theoretical information about PMD and optical fiber spinning process, different spin profiles are examined. Comparative analysis of spin profiles is made and spin parameters giving successful results for low-PMD fibers are obtained for each spin profile. Simulation results show that for fixed spin period of 1 m 2.76 turns/m and 5.64 turns/m are proper spin amplitude values for sinusoidal and amplitude modulated (AM) spin profiles, respectively, while 3.40 turns/m and 3.75 turns/m are recommended spin amplitudes for triangular and trapezoidal spin profiles, respectively. Using these parameters, related spin profiles give better differential group delay (DGD) reduction results individually.
Fresnel reflection based fiber optic refractive index sensor for liquid concentration dedection
(IEEE, 2014) Başgümüş, Arif; Durak, Fırat Ertaç; Sadık, Şerif Ali; Altuncu, Ahmet; Ebeoǧlu, Mehmet Ali; Yılmaz, Güneş; Uludağ Üniversitesi/Mühendislik Fakültesi/ Elektrik-Elektronik Mühendisliǧi Bölümü.; 0000-0001-8972-1952; AAH-4182-2021; 7004543197
Measurement of refractive index which is one of the distinctive properties of materials is commonly used in many fields such as quality control of food industry, biomedical applications, biochemical analysis and measurement of environmental pollution. From the refractive index measurement methods, the one based on fiber optic stands out with their provided advantages. In this study, firstly, a simple, reliable and highly sensitive Fresnel reflection based fiber optic refractometer was setup, then the refractive indexes of various liquids were measured using this setup at different times. When the measurement results are compared with material science data sheet (MSDS) values, the percent error was found to be less than %1. Moreover, the long term stability of ethanol's refractive index was examined and the refractive index variation of salt-water was obtained as a function of the salt concentration.
Fresnel yansıma tabanlı fiber optik sensör sistemi tasarımı ve röle destekli serbest uzay optik haberleşme sistemi ile iletim optimizasyonu
(Uludağ Üniversitesi, 2016-02-01) Başgümüş, Arif; Yılmaz, Güneş; Altuncu, Ahmet; Uludağ Üniversitesi/Fen Bilimleri Enstitüsü/Elektronik Mühendisliği Anabilim Dalı.
Bu tez çalışmasında, sıvıların kırılma indisini gerçek zamanlı olarak ölçebilen Fresnel yansıma tabanlı fiber optik sensör dizisi tasarlanmış ve deneysel karakterizasyonu yapılmıştır. Sensör dizisi tasarımı için, optik fiberlerde darbelerin zamanda çoğullamasını sağlayan iletim süresi optimizasyonu gerçekleştirilmiştir. Laboratuvar ortamında gerçekleştirilen ölçümlerde, sudaki tuz yoğunluğunun kırılma indisine bağlı değişiminin, uygunluk derecesi 1'e çok yakın olacak şekilde doğrusal elde edilmesi, ölçüm sisteminin doğrusallığını göstermektedir. Bu çalışmada ayrıca, farklı çözücülerin kırılma indisleri yüksek çözünürlükle ölçülmüş ve literatürde verilen değerlerle karşılaştırılmıştır. Tasarlanan ölçüm sisteminin kısa ve uzun dönem kararlılık performanslarının yüksek olduğu gösterilmiştir. Fresnel yansıma tabanlı fiber optik sensör sisteminden alınan veriler, uzak alıcılara bir röle destekli serbest uzay optik (FSO) haberleşme sistemi üzerinden iletilebilir. Bu amaçla, FSO haberleşme sisteminin iletim mesafesi performans analizi ayrıca çalışılmıştır. Bu çalışmada, farklı konfigürasyonlardaki röle destekli FSO haberleşme sistemlerinin, atmosferik çalkantı ve yol kaybı tesirleri altında kesinti olasılığı incelenmiştir. Buradan yola çıkılarak iletim mesafesi için bir optimizasyon problemi tanımlanmış ve bu problem Matlab™ programı kullanılarak, diferansiyel gelişim (DE) ve parçacık sürü optimizasyonu (PSO) algoritmaları ile çözülmüştür. Normal şartlar altında kabul edilebilir düzeydeki kesinti olasılığı için en büyük iletim mesafeleri, yazılan benzetim programları sayesinde en uygun röle konum kestirimi yapılarak elde edilmiştir. Ayrıca, bu iki algoritmanın FSO haberleşme sistemlerindeki karşılaştırmalı performans analizi detaylı olarak gerçekleştirilmiştir.
A novel spin profile for low polarization mode dispersion
(National Institute of Optoelectronics, 2016-11-25) Sadık, Şerif Ali; Altuncu, Ahmet; Karlık, Sait Eser; Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.; AAJ-2404-2021; 10043513300
Theoretical basis of spun fibers and their ability to reduce Polarization Mode Dispersion (PMD) are discussed. In order to overcome PMD-based problems, Amplitude Modulation Transmitted Carrier (AM-TC) profile is proposed. A comparative analysis of spin profiles is made and spin parameters giving successful results for low-PMD fibers are obtained. Simulation results show that for spin period of I m and spin amplitude of 2.76 turns/in, the proposed AM-TC spin profile provides better PMD reduction results than the conventional ones. For different modulation index values of the AM-TC spin profile, the differential group delay (DGD) obtained is under 1.4 fs.
Optimization of spin parameters for spun fibers having low polarization mode dispersion
(Elsevier Science Inc, 2019-09-01) Sadık, Şerif Ali; Temurtaş, Hasan; Altuncu, Ahmet; Karlık, Sait Eser; KARLIK, SAİT ESER; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik ve Elektronik Mühendisliği Bölümü.; AAJ-2404-2021
Polarization mode dispersion (PMD) is a dispersive effect caused by the birefringence of the optical fiber. Spinning the fiber with periodic profiles during the drawing process from preform is known as a PMD-reducing process. In this paper, common spin parameters giving successful results in obtaining low PMD for three spin profiles, i.e. sinusoidal, amplitude modulation-suppressed carrier (AM-SC) and amplitude modulation-transmitted carrier (AM-TC), are searched and an optimization problem based on this research is defined. This optimization problem is solved by using Differential Evolution Algorithm (DEA) and common spin parameters suitable for all discussed spin profiles are obtained. For all spin profiles, optimum common spin parameters are found to be 8.81 turns/m for the spin amplitude and 3.69 m for the spin period. Numerical analysis performed with those optimum spin parameters show that in the short fiber regime the differential group delay (DGD) takes a value under 0.25 fs and the mean DGD value remains lower than 15 fs in long lengths of fiber. The obtained results show that PMD reduction with respect to unspun fibers can be achieved by using optimized spin profiles even in the case of random mode coupling.
Optimum transmission distance for relay-assisted free-space optical communication systems
(Elsevier, 2016-04-16) Başgümüş, Arif; Hiçdurmaz, Bahadır; Temurtaş, Hasan; Namdar, Mustafa; Altuncu, Ahmet; Yılmaz, Güneş; Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.; 7004543197
In this paper, optimum transmission distances are obtained for different relay nodes in the serial and parallel decode-and-forward relaying schemes by using differential evolution algorithm in free-space optical communication systems. The transmission distances are investigated by optimizing the place of the relay nodes at a target outage probability of 10(-6). In this study, the numerical results reveal that the optimum transmission distances are increased for both the whole power margins and different number of relay nodes with the help of the proposed optimization technique.
Performance comparison of the differential evolution and particle swarm optimization algorithms in free-space optical communications systems
(Univ Suceava, 2015) Başgümüş, Arif; Namdar, Mustafa; Altuncu, Ahmet; Yılmaz, Günes; Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.; 0000-0001-8972-1952; AAH-4182-2021; 7004543197
In this comparative study we evaluate the performance of Differential Evolution (DE) and Particle Swarm Optimization (PSO) algorithms in free space optical communications systems. In particular we obtain the optimal transmission distances for different relay nodes in the parallel decode-and-forward relaying schemes by optimizing the relay placements. We analyze that the cost functions are suitably minimized. Then we investigate the execution time and the stability of the DE and PSO algorithms for decode-and-forward relay-assisted free space optical links. The simulation results demonstrate that the PSO algorithm outperforms DE algorithm in terms of the minimization of the cost function. Furthermore the results indicate that we get the similar performance for the execution-time and optimization results in the DE and PSO algorithms.
A universal and stable all-fiber refractive index sensor system
(IEEE-Inst Electrical Electronics Engineers, 2016-01-15) Durak, Fırat Ertaç; Altuncu, Ahmet; Yılmaz, Güneş; Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.; 7004543197
In this letter, a universal, simple, and stable all-fiber sensor system is proposed to measure the refractive index (RI) of liquids. The basic principle of the technique is based on the relative measurement of the Fresnel reflection from sensor probes. A quadruple of time-division multiplexed Fresnel reflected pulses are obtained from a single nanosecond input pulse owing to the latencies in fibers with different lengths. The measured RIs for the different liquids show that the proposed all-fiber RI sensor system enables linear and repeatable measurements. The performance of the system is compared with the previously published studies, and good agreement is observed, showing the accuracy of the measurements. The standard deviations of the measured RIs are obtained in a short-term measurement as 2.8 x 10(-6) for distilled water, and in a long-term measurement as 2.99x10(-5) for methanol, showing the high repeatability of the measurements.