Browsing by Author "Arpali, Serap Altay"

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A comparison of iterative Fourier transform algorithms for image quality estimation
(2018) Alsaka, Dina Yaqoob; Arpali, Çağlar; Arpali, Serap Altay; 20809; 06.08. Mekatronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A comparison was established between two iterative Fourier transform algorithms (IFTAs), such as the original Gerchberg–Saxton (GS) and the mixed-region amplitude freedom (MRAF) algorithms, for the hologram reconstruction of different target images through the full reference image quality estimation (IQE) and pixel homogeneity in the Fourier plane presented theoretically and experimentally. The comparison was applied depending upon both algorithms based on a computer-generated hologram (CGH) implemented utilizing a reflective phase-modulated liquid-crystal spatial light modulator (LC-SLM) to obtain the digital kinoform holograms of the desired intensity distributions. These digital holograms were applied to reconstruct the intensity patterns for 852 nm, which represents a laser beam source. The theoretical and experimental results of the reconstructed patterns obtained using the MRAF algorithm were found to be smoother and better than the patterns obtained using the GS algorithm. Unmodulated light beam (dc term) is removed from the reconstructed patterns attributed to digital kinoform holograms of MRAF algorithm as an alternative to the theoretical and experimental results without using any additional optic equipment at the light path. Moreover, this paper discussed the full reference objective quality estimations, such as mean square error (MSE), peak signal-to-noise ratio (PSNR), structural content (SC), normalized absolute error (NAE), normalized cross correlation (NK), and homogeneity of pixels, through the contrast (Cont) and inverse difference moment (IDM) for numerical and experimental results. According to the two desired intensity distributions processed theoretically and experimentally, the results of MRAF algorithm were found to be in the highly accurate recovered phase, the quality of image was enhanced, and the dc term was decreased. Image quality estimation of full reference objective relay on the feedback algorithms experimental attestation has not been implemented yet.
Citation - WoS: 29
Citation - Scopus: 35
Ber Evaluations for Multimode Beams in Underwater Turbulence
(Taylor & Francis Ltd, 2016) Arpali, Serap Altay; Baykal, Yahya; Arpali, Caglar; 7812; 06.02. Elektronik ve Haberleşme Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In underwater optical communication links, bit error rate (BER) is an important performance criterion. For this purpose, the effects of oceanic turbulence on multimode laser beam incidences are studied and compared in terms of average BER (< BER >), which is related to the scintillation index. Based on the log-normal distribution, < BER > is analysed for underwater turbulence parameters, including the rate of dissipation of the mean squared temperature, the rate of dissipation of the turbulent kinetic energy, the parameter that determines the relative strength of temperature and salinity in driving index fluctuations, the Kolmogorov microscale length and other link parameters such as link length, wavelength and laser source size. It is shown that use of multimode improves the system performance of optical wireless communication systems operating in an underwater medium. For all the investigated multimode beams, decreasing link length, source size, the relative strength of temperature and salinity in driving the index fluctuations, the rate of dissipation of the mean squared temperature and Kolmogorov microscale length improve the < BER >. Moreover, lower < BER > values are obtained for the increasing wavelength of operation and the rate of dissipation of the turbulent kinetic energy in underwater turbulence.
Citation - WoS: 2
Citation - Scopus: 3
Ber for Higher Order Laser Modes in Optical Wireless Underwater Communications
(Ieee, 2016) Arpali, Serap Altay; Baykal, Yahya; Arpali, Caglar; 51304; 7812; 20809; 06.02. Elektronik ve Haberleşme Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Average bit error rate () of an underwater optical communication system is analyzed for higher order laser beams. For this purpose, the effects of oceanic turbulence parameters and link parameters on single mode higher order laser beams are investigated.
Citation - WoS: 8
Citation - Scopus: 7
Bit Error Rate of a Gaussian Beam Propagating Through Biological Tissue
(Taylor & Francis Ltd, 2020) Arpali, Serap Altay; Arpali, Caglar; Baykal, Yahya; 7812; 51304; 20809; 06.08. Mekatronik Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The scintillation index and bit error rate (BER) of a Gaussian beam propagating in a weakly turbulent soft tissue are formulated and analysed numerically. The scintillation indices are plotted against half of the measured slope in the range of power-law scaling at different tissue parameters, such as the random variations in the refractive index of the tissue, outer scale of the tissue turbulence and the tissue length between the optical source and the detector. Moreover, BERs of Gaussian beams against the signal to noise ratio (SNR) are examined for different tissue parameters. Our graphical results show that the scintillation index and BER increase with larger outer scales, longer tissue lengths and larger random variations in the refractive index of the tissue. In comparison with the spherical wave propagation, it was found that Gaussian beam yields larger scintillation index and BER values.
Citation - WoS: 2
Bit Error Rates for Focused General-Type Beams
(Electromagnetics Acad, 2009) Arpali, Serap; Arpali, Serap Altay; Baykal, Yahya Kemal; Baykal, Yahya; 51304; 7812; Elektrik-Elektronik Mühendisliği; Elektronik ve Haberleşme Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Using the scintillation index of general beam formulation, bit error rate (BER) is investigated for focused Gaussian, cos-Gaussian, cosh-Gaussian and annular beams in weak atmospheric turbulence. We have employed our previously derived formulation of the scintillation index of these beams by Rytov method. Rytov method scintillation theory is known to yield accurate results for focused beams on horizontal paths under certain regions. Therefore we find the scintillation indices of the mentioned beams for the valid region. Using the log-normal distributed intensity, BER values versus signal-to-noise ratio (SNR) are calculated for Gaussian, cos-Gaussian, cosh-Gaussian and annular beams. In our study, the focal lengths (radius of curvature) of all the mentioned focused beams are equal to the propagation distance. The improvement of BER is observed for variations of propagation length, source size and wavelength of operation. Based on these parameters, BER values of Gaussian, cos-Gaussian, cosh-Gaussian and annular beams are compared. BER values we found for the focused Gaussian, cos-Gaussian, cosh-Gaussian and annular beams decrease with increasing source sizes. Likewise, BER values of focused Gaussian, cos-Gaussian, cosh-Gaussian and annular beams decrease with increasing wavelength. The focused annular beam attains the lowest BER value for small source sizes and long propagation distances. Moreover, BER for focused beams is compared with their collimated counterparts. We observe that focused beams have lower BER values than the collimated beams on horizontal paths. Our formulation can easily be extended to cover corresponding higher order beams, however in this paper we concentrate mainly on the zero order beams.
Citation - WoS: 28
Citation - Scopus: 28
Bit Error Rates for General Beams
(Optical Soc Amer, 2008) Arpali, Serap Altay; Eyyuboglu, Halil T.; Baykal, Yahya; 51304; 7688; 7812; 06.02. Elektronik ve Haberleşme Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In order to analyze the effect of beam type on free space optical communication systems, bit error rate (BER) values versus signal-to-noise ratio (SNR) are calculated for zero order and higher order general beam types, namely for Gaussian, cos-Gaussian, cosh-Gaussian, and annular beams. BER analysis is based on optical scintillation using log-normal distribution for the intensity, which is valid in weak atmospheric turbulence. BERs for these beams are plotted under variations of propagation length, source size, wavelength of operation, and order of the beam. According to our graphical outputs, at small source sizes and long propagation distances, the smallest BER value is obtained for the annular beam. On the other hand, at large source size and small propagation distance, the smallest BER value is obtained for the cos-Gaussian beam, Moreover, our study of the order of the beam shows that higher order beams have lower BER values than the zero order beams at longer propagation distances. But this drop compared with the order seems to be incremental. (c) 2008 Optical Society of America
Citation - WoS: 20
Citation - Scopus: 21
A Comparison of Iterative Fourier Transform Algorithms for Image Quality Estimation
(Optical Soc Japan, 2018) Alsaka, Dina Yaqoob; Arpali, Caglar; Arpali, Serap Altay; 20809; 06.08. Mekatronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A comparison was established between two iterative Fourier transform algorithms (IFTAs), such as the original Gerchberg-Saxton (GS) and the mixed-region amplitude freedom (MRAF) algorithms, for the hologram reconstruction of different target images through the full reference image quality estimation (IQE) and pixel homogeneity in the Fourier plane presented theoretically and experimentally. The comparison was applied depending upon both algorithms based on a computer-generated hologram (CGH) implemented utilizing a reflective phase-modulated liquid-crystal spatial light modulator (LC-SLM) to obtain the digital kinoform holograms of the desired intensity distributions. These digital holograms were applied to reconstruct the intensity patterns for 852 nm, which represents a laser beam source. The theoretical and experimental results of the reconstructed patterns obtained using the MRAF algorithm were found to be smoother and better than the patterns obtained using the GS algorithm. Unmodulated light beam (dc term) is removed from the reconstructed patterns attributed to digital kinoform holograms of MRAF algorithm as an alternative to the theoretical and experimental results without using any additional optic equipment at the light path. Moreover, this paper discussed the full reference objective quality estimations, such as mean square error (MSE), peak signal-to-noise ratio (PSNR), structural content (SC), normalized absolute error (NAE), normalized cross correlation (NK), and homogeneity of pixels, through the contrast (Cont) and inverse difference moment (IDM) for numerical and experimental results. According to the two desired intensity distributions processed theoretically and experimentally, the results of MRAF algorithm were found to be in the highly accurate recovered phase, the quality of image was enhanced, and the dc term was decreased. Image quality estimation of full reference objective relay on the feedback algorithms experimental attestation has not been implemented yet.
Citation - WoS: 7
Citation - Scopus: 6
Dynamic Flat-Topped Laser Beam Shaping Method Using Mixed Region Amplitude Freedom Algorithm
(Springer Heidelberg, 2022) Arpali, Caglar; Arpali, Serap Altay; Altemimi, Mohammed Fawzi; Alsaka, Dina Yaqoob; 20809; 06.08. Mekatronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A dynamic beam shaping method is proposed for the generation of flat-top beams (FTBs) in the far field. Using the mixed-region amplitude freedom algorithm, this new method is used to design the required phase distribution encoded on a spatial light modulator for the generation of FTB profiles. The characteristics of these new beam shaping methods are used as beam parameters, such as the laser beam size, the beam intensity of square FTBs, and the root-mean-square error (RMSE). Using our proposed method, the theoretical performance of beam intensity shaping is improved to an RMSE < 0.02 with a minimum number of iterations of phase reconstruction. Using the phase hologram of dynamic beam shaping, theoretical and experimental comparisons of edge steepness and plateau uniformity were established for the square FTBs of variable beam sizes. It is shown that the dynamic beam shaping of FTBs can produce high intensity uniformity in the plateau region with steep edges, which makes it an effective tool, especially for laser machining applications.
Citation - WoS: 4
Citation - Scopus: 11
Effects of Focused and Collimated Laser Beams on the Performance of Underwater Wireless Optical Communication Links
(Ieee, 2015) Catmakas, Omer Kemal; Genc, Fatih; Baykal, Yahya; Arpali, Serap Altay; Arpali, Caglar; Keskin, Aysan; 06.08. Mekatronik Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this paper, the optical transmittance and bit error rate (BER) of focused and collimated laser beams are experimentally examined in an underwater optical wireless communication link with different water types. The water types used are fresh water, salty water and their variations with maalox in order to obtain turbid water. In bit error rate (BER) analysis, on-off keying (OOK) is used together with Bose-Chaudhuri-Hocquenghem (BCH) and convolutional codes. Results show that salt and maalox content decreases the transmittance, the convolution codes have better BER performance than BCH codes under the same modulation scheme (i.e., OOK) and focusing improves both the transmittance and BER performance as compared to collimated beams.
Fluorescent On-Chip Imager by Using a Tunable Absorption Filter
(Ieee, 2017) Arpali, Caglar; Yıldırım, Ender; Yildirim, Ender; Arpali, Çağlar; Arpali, Serap Altay; Arpali, Serap; 20809; 31835; 51304; Makine Mühendisliği; Mekatronik Mühendisliği; Elektronik ve Haberleşme Mühendisliği; 06.06. Makine Mühendisliği; 06.08. Mekatronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
High-Throughput Screening of Blood Samples Based on Structured Illumination On-Chip Imaging
(Ieee, 2013) Arpali, Serap Altay; Arpali, Caglar; Coskun, Ahmet F.; Chiang, Hsin-Hao; Ozcan, Aydogan; 06.08. Mekatronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
We demonstrate a high-throughput fluorescent on-chip imaging platform, using structured illumination that can rapidly screen large volumes of scattering media such as undiluted whole blood samples (e.g., similar to 0.3-0.7 mL) for detection of fluorescent micro-objects at low concentrations (e.g., <= 50-100 particles/mL). This imaging modality might especially be useful for rare cell applications involving whole blood samples, such as detection of circulating tumor cells.
Citation - WoS: 47
Citation - Scopus: 50
High-Throughput Screening of Large Volumes of Whole Blood Using Structured Illumination and Fluorescent On-Chip Imaging
(Royal Soc Chemistry, 2012) Arpali, Serap Altay; Arpali, Caglar; Coskun, Ahmet F.; Chiang, Hsin-Hao; Ozcan, Aydogan; 51304; 06.02. Elektronik ve Haberleşme Mühendisliği; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Undiluted blood samples are difficult to image in large volumes since blood constitutes a highly absorbing and scattering medium. As a result of this limitation, optical imaging of rare cells (e.g., circulating tumour cells) within unprocessed whole blood remains a challenge, demanding the use of special microfluidic technologies. Here we demonstrate a new fluorescent on-chip imaging modality that can rapidly screen large volumes of absorbing and scattering media, such as undiluted whole blood samples, for detection of fluorescent micro-objects at low concentrations (for example <= 50-100 particles/mL). In this high-throughput imaging modality, a large area microfluidic device (e.g., 7-18 cm(2)), which contains for example similar to 0.3-0.7 mL of undiluted whole blood sample, is directly positioned onto a wide-field opto-electronic sensor-array such that the fluorescent emission within the microchannel can be detected without the use of any imaging lenses. This microfluidic device is then illuminated and laterally scanned with an array of Gaussian excitation spots, which is generated through a spatial light modulator. For each scanning position of this excitation array, a lensfree fluorescent image of the blood sample is captured using the opto-electronic sensor-array, resulting in a sequence of images (e.g., 144 lensfree frames captured in similar to 36 s) for the same sample chip. Digitally merging these lensfree fluorescent images based on a maximum intensity projection (MIP) algorithm enabled us to significantly boost the signal-to-noise ratio (SNR) and contrast of the fluorescent micro-objects within whole blood, which normally remain undetected (i.e., hidden) using conventional uniform excitation schemes, involving plane wave illumination. This high-throughput on-chip imaging platform based on structured excitation could be useful for rare cell research by enabling rapid screening of large volume microfluidic devices that process whole blood and other optically dense media.
Citation - WoS: 6
Citation - Scopus: 11
Implementation and Characterization of an Absorption Filter for On-Chip Fluorescent Imaging
(Elsevier Science Sa, 2017) Arpali, Caglar; Arpali, Serap Altay; Yildirim, Ender; 31835; 20809; 51304; 06.08. Mekatronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi; 06.06. Makine Mühendisliği
Here we present fabrication and characterization of an absorption filter with superior roll-on properties and precisely tunable cut-off wavelengths for fluorescent imaging applications in lab-on-a-chip systems. The filters were fabricated by spinning dye doped photopolymer (Orasol Yellow in Norland Optical Adhesive 60) on glass substrates. The fabrication technique allowed us to precisely tune the cut-off wavelength of the filters. We showed that filters with different cut-off in the range of 386 nm-504 nm could be obtained simply by controlling the settling time before spinning. The filters exhibited a steep roll-on from stopband to passband at the cut-off. Transmission in the stopband was observed to be maximum 3% while it was almost constant at 100% in the passband within the range of 220 nm-620 nm. On-chip use of the filters was also demonstrated for imaging particular fluorescent beads. (C) 2016 Elsevier B.V. All rights reserved.
Kanserin Erken Teşhisi için Yapısal Aydınlatma Tekniğine Dayanan Floresan Etiketlemeli On-Chip Görüntüleme Platformunun Geliştirilmesi
(2016) Baykal, Yahya Kemal; Özcan, Aydoğan; Arpali, Serap Altay; Arpali, Çağlar; 01. Çankaya Üniversitesi
Bu projede kanser hastalıklarının erken tanısında kullanılmak üzere yapısal aydınlatma tekniğine dayanan floresan etiketlemeli on-chip görüntüleme sistemi geliştirilmiştir. Geliştirilen bu görüntüleme platformu ile kan değişik türde ki bir ışık paterniyle hızlı bir şekilde taranmakta ve floresan boya ile etiketlenmesi yapılmış düşük yoğunluktaki kanser hücreleri tespit edilebilmektedir. Bu sistem, aydınlatma tekniği, görüntüleme yöntemi, optik tasarım ve kan analizi için biyo-kanal geliştirilmesi bakımından bir dizi yenilik içermektedir. Bu projede klasik aydınlatmanın (düzlem dalga) yerine Gauss ve Bessel gibi yeni türde yapısal ışık kaynakları kullanılmıştır. Bu ışık paternleri, kan gibi yoğun ve saçıcı ortamlarda kanser hücrelerine ulaşarak ışık aktarımını mümkün kılmaktadır. Bu platform, görüntüleme yöntemi açısından klasik sistemlerden farklı olup kan örneği direk olarak görüntüleme sensörü CCD (charge coupled device) üzerine konulmaktadır (On-Chip). Ayrıca görüntüleme platformlarının yaşadığı düşük Sinyal Gürültü Oranı (SNR) problemini çözmek için özel bir algoritmayla görüntünün iyileştirilmesi hedeflenmiştir. Yapısal ışık paterninin üretilmesi ve kanın taranması, tasarladığımız optik bir sistem tarafından yapılmaktadır. Lazer uzamsal ışık modülatörüyle (UIM) modüle edilmekte ve özel algortimalar aracılığıyla ışık yapısal forma dönüştürülmektedir. Daha sonra bu ışık bir lens sistemi tarafından içinde kanın bulunduğu biyo-kanal üzerine aktarılmaktadır. Bu projede yüksek hacimde kanı (2 ml ye kadar) içine alabilen ve geniş yüzeyi sayesinde yaklaşık 9 cm2 lik bir alanda tarama yapmayı mümkün kılan tek kullanımlık ve maliyeti düşük bant temelli biyo-kanallar üzerinde çalışılmış ve üretimi gerçekleştirilmiştir. Bu görüntüleme platformuyla etiketlemesi yapılmış değişik oranlardaki Beyaz Kan hücreleri ve K562 Kornik Myleoid Lösemi hücreleri kan içinde tespit edilmiştir. Son aşamada elde edilen sonuçlar klasik mikroskopla elde edilen deney sonuçlarıyla kıyaslanarak geliştirilen sistemin başarım oranı raporlanmıştır. Bu projede ayrıca, küresel, düzlem ve yapısal Gauss ışık kaynaklarının kan ve doku gibi biyolojik ortamlarda yayılması neticesinde ortaya çıkan ışık şiddeti salınımları (sintilasyon), zayıf türbülanslı yumuşak doku için formüle edilmiş ve doku uzunluğu, kırılma endeksindeki rastgele değişimler ve dalga boyu gibi parametrelere göre de kıyaslanmıştır.
Citation - WoS: 1
Citation - Scopus: 1
Propagation of Higher-Order Annular Gaussian Beams in Biological Tissues
(Optica Publishing Group, 2025) Arpali, Serap Altay; Baykal, Yahya Kemal; 06.02. Elektronik ve Haberleşme Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The propagation characteristics of a higher-order annular Gaussian (HOAG) beam in biological tissue turbulence are investigated. Average intensity at the receiver plane is found when the HOAG source field is used as excitation. The effects of the HOAG beam on different tissue types of the upper dermis (human), liver parenchyma (mouse), intestinal epithelium (mouse), and deep dermis (mouse) are studied. Variations of the average intensity versus the source and medium parameters such as the strength coefficient of the refractive-index fluctuations, propagation distance, wavelength, and beam size are presented. The results show that all modes of the HOAG beam can successively transmit beam energy at different levels of turbulence for all tissue types. At the same turbulence strength, HOAG beams having larger mode numbers transmit higher intensity to receivers than the modes with smaller mode orders, which is valid for all the examined tissue types. As the strength of tissue turbulence increases, the HOAG beam slowly turns into a pure Gaussian beam. For the different tissue types, the highest beam intensity at the receiver was observed for the deep dermis (mouse) tissue type. Despite the change in wavelength, refractive-index fluctuations, and source beam size, the highest beam transmission through the tissue in a turbulent environment was also observed for this same tissue type. This research may be useful in understanding the fundamentals of lighttissue interaction of HOAG laser beams, which may improve noninvasive disease detection and therapy methods through tissue in biophotonic technologies. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.
Citation - WoS: 49
Citation - Scopus: 47
Scintillation Index of Higher-Order Cos-Gaussian, Cosh-Gaussian and Annular Beams
(Taylor & Francis Ltd, 2008) Arpali, Serap Altay; Eyyuboglu, Halil T.; Baykal, Yahya; 51304; 7688; 7812; 06.02. Elektronik ve Haberleşme Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this paper, via the generalized beam formulation, we evaluate the scintillation index for higher-order general beams propagating through the weak atmospheric turbulence. The investigated higher-order beam types are cos-Gaussian, cosh-Gaussian and annular beams. The scintillation indices of these beams are plotted with respect to propagation length, source size and order of the beam. According to our graphical outputs, higher-order beams have less on-axis scintillation index than zero-order beams at longer propagation distances. The on-axis scintillation exhibits a slight increase when the order of even-ordered beams is made higher. Moreover, our study on the source size variation shows that, for most of the source size range, cos-Gaussian beams have a lower scintillation index than the other beams.
Citation - WoS: 22
Citation - Scopus: 20
Scintillation Index of Optical Spherical Wave Propagating Through Biological Tissue
(Taylor & Francis Ltd, 2017) Baykal, Yahya; Arpali, Caglar; Arpali, Serap Altay; 7812; 20809; 51304; 06.03. Elektrik-Elektronik Mühendisliği; 06.08. Mekatronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Effects of the tissue turbulence on the propagation of an optical spherical wave are analysed. For this purpose, scintillation index of an optical spherical wave which is propagating in a soft tissue is formulated and evaluated in weakly turbulent soft tissue. Scintillation index of the optical spherical wave is examined against the changes in the tissue parameters which are the tissue length between the optical spherical wave source and the detector, random variations in the refractive index of the tissue and the outer scale of the tissue turbulence. According to our graphical outputs, it is observed that increase in the random variations of the refractive index of the tissue results in an increase in the scintillation index at a certain realization of the turbulence spectrum. On the other hand, larger outer scales and longer tissue lengths yield larger scintillations. The variation of the scintillation index of the optical spherical wave versus the wavelength is also investigated. It is found that at small tissue lengths, wavelength has almost no effect on the scintillations; however, when the tissue length reaches a certain value, shorter wavelengths give rise to larger intensity fluctuations.
Citation - WoS: 77
Citation - Scopus: 73
Simulator for General-Type Beam Propagation in Turbulent Atmosphere
(Optical Soc Amer, 2006) Arpali, Caglar; Yazicioglu, Canan; Eyyuboglu, Halil Tanyer; Arpali, Serap Altay; Baykal, Yahya; 7688; 7812; 51304; 06.08. Mekatronik Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A simulator is designed in MATLAB code which gives the propagation characteristics of a general-type beam in turbulent atmosphere. When the required source and medium parameters are entered, the simulator yields the average intensity profile along the propagation axis in a video format. In our simulator, the user can choose the option of a "user defined beam" in which the source and medium parameters are selected as requested by the user by entering numerical values in the relevant menu boxes. Alternatively, the user can proceed with the option of "pre-defined beam" in which the average intensity profiles of beams such as annular, cos-Gaussian, sine-Gaussian, cosh-Gaussian, sinh-Gaussian, their higher-order counterparts and flat-topped can be observed as they propagate in a turbulent atmosphere. Some samples of the simulator output are presented. (c) 2006 Optical Society of America
Sualtı Optik Kablosuz Haberleşme Sistemi Tasarımı ve Uygulaması
(2016) Gerçelcioğlu, Hamza; Arpali, Çağlar; Arpali, Serap Altay; Baykal, Yahya; 01. Çankaya Üniversitesi
Sualtı ortamında kablosuz haberleşme çoğunlukla düşük veri oranlarındaki ses dalgalarıyla gerçekleştirilmektedir. Endüstri, bilimsel ve savunma alanlarındaki ihtiyaçlar, sualtında yüksek veri hızına sahip iletişimi gerektirmektedir. Sualtı kablosuz optik haberleşme sistemleri bu ihtiyacı karşılamak üzere önerilmiş ve okyanusta kirlilik tespiti, petrol ve gaz rezervlerinin izlenmesi, sismik gözlemler, petrol ve gaz boru hatlarının kurulum ve işletimi, sensörlü ağ iletişimi, gemi-denizaltı haberleşmesi gibi alanlarda kullanılmaya başlamıştır. Suyun karmaşık doğasından dolayı sualtında kablosuz optik iletişim bir çok zorluk içerir. Su ışığın yayılmasına büyük bir engel teşkil eder ve bu durum optik geçirgenliğin onlarca metreyle ifade edilebilen kısa mesafelere inmesiyle sonuçlanır. Deniz suyu, okyanus suyu, sığ su, liman suyu gibi farklı su tiplerinden oluşan sualtı ortamında optik geçirgenliğin davranışı dalga boyuna göre incelendiğinde büyük değişiklikler gösterir. Suda bulunan çeşitli bileşenlerden dolayı oluşan saçılım, emilim ve ısı ile tuzluluk salınımlarından kaynaklanan sualtı türbülansı, gelen ışığı bozarak veri aktarım hızlarında kayda değer düşüşlere sebep olur. Bu projede mevcut sualtı kablosuz optik haberleşme sistemlerinin performansını modülasyon, kodlama, kanal kestrimi ve değişik tip ışık hüzmeleri kullanarak ilerletecek yöntemler sunulmuştur. Sığ okyanus suyu kullanılarak sualtı kablosuz optik haberleşme linki laboratuvar ortamında kurulmuş ve 12 Mbit/s veri iletimi sağlanmıştır. Teorik ve deneysel olarak uygun optik geçirgenlik pencereleri dalga boyuna göre araştırılmış ve pırıldama indisi ile belirlenen ışık şiddeti salınımları ve Bit Hata Oranı (BER) açısından sistemin değerlendirmesi yapılmıştır. Bu kapsamda düzlemsel, küresel ışık dalgaları ve farklı ışık hüzmeleri için pırıldama indisi formüle edilip link uzunluğu, dalgaboyu, Kolmogorov mikro ölçek uzunluğu, sıcaklık ve tuzluluk salınımları gibi parametreler açısından incelenmiştir. Bunlara ek olarak farklı modülasyon (M-QAM v.b.) ve kodlama tekniklerinin (BCH v.b.) veri iletişimini nasıl etkilediği araştırılmış, kanal kestrimi ile kanal denkleştirmenin BER’i oldukça düşürdüğü ve oldukça uzun mesafelerde iletişime olanak sağladığı tespit edilmiştir. Ayrıca farklı tipde ışık hüzmeleri kullanmanın (çapraz, çok modlu, odaklanmış Gauss v.b) sualtı kablosuz optik haberleşme sistemlerinde performansı iyileştirdiği gözlenmiştir.
Yumuşak Doku İçerisinde Yayılan Küresel Dalganın Performans Analizi
(2021) Arpali, Serap Altay; 51304; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Bu çalışmada, yumuşak doku içerisinde yayılan küresel dalganın performansını analiz edebilmek için, optiksel küresel dalganın bit-hata-olasılığını (BER) inceledik. Bu kapsamda, optiksel küresel dalganın ortalama BER’i (), yumuşak dokunun kırınım indeksindeki rastgele değişimleri, kaynak ve detektör arasındaki doku uzunluğu, büyük ölçekli doku türbülansı gibi değişik doku ve türbülans parametrelerine bağlı olarak ayrıntılı olarak çalışılmıştır. Çalışmanın sonucunda doku türbülansının büyük ölçek değeri, doku uzunluğu ve yumuşak dokunun kırınım indeksindeki rastgele değişimleri arttıkça değeri artmıştır. Ayrıca optiksel küresel dalganın değerleri üstel ölçek kuralının sınırları içinde belirlenen eğimin yarı değerinin farklı büyüklükleri için incelenmiştir. Üstel ölçek kuralının sınırları içinde belirlenen eğimin yarı değerinin farklı büyüklüklerinin azalan değerleri için küresel dalganın ’nin düştüğü gözlemlenmiştir.