1,721,017 research outputs found
Fiber optik sensör içeren yeraltı radarı ile gömülü olan silindirik cismin tespiti.
No full textThe terms ‘ground-probing radar’, ‘ground penetrating radar (GPR)’, ‘sub-surface radar’ or ‘surface-penetrating radar (SPR)’ refer to various techniques for detecting and imaging of subsurface objects. Among those terms GPR is preferred and used more often. In this thesis, the depth and the position of the buried circular cylinder are determined by a GPR system which comprises of an optical fiber sensor (OFS). The system is a combination of OFS, GPR and optical communication link. In order to determine the depth and the position, first of all the electric field distribution at the OFS is obtained by integrating the Green’s function over the induced current distribution. Those distributions are observed for different frequency and depth values. The voltages inside the distribution are measured by OFS. By changing the depth of the cylinder and the frequency of the system, various plots showing x axis displacement versus measured voltages are obtained. Those plots are related to interference fringe patterns. The position and the depth of the cylinder are obtained using interference fringe patterns. All of the studies mentioned are performed in MATLAB R2007b program. The noises of the system due to OFS are extracted using OPTIWAVE OPTISYSTEM 7.0 program. By adding those noises to the measured voltage values, the operating frequency of the system is observed.M.S. - Master of Scienc
Malzeme işleme için 60 w darbeli fiber lazer yükselteci geliştirilmesi.
No full textFiber lasers have the advantage of high beam quality, high efficiency, small size, air cooling and therefore much interest in the development of high power fiber laser systems have arisen recently in the world. Almost all commercially developed fiber lasers with nanosecond pulse duration, that are being used for material processing, are Q-switched systems. Vital parameters in the material processing such as repetition rate, pulse energy and pulse duration are correlated with each other and they cannot be adjusted independently in the Q-switch mechanism. In this study, ytterbium doped all-fiber laser amplifier with 60 W average power and more than 20 kW peak power at 1 μm wavelength was developed, and its potential for processing of different material types is investigated. This master-oscillator power-amplifier (MOPA) architectured system is composed of pulses, produced by an electronically pumped diode, and amplified by a series of fiber amplifiers. In contrast with Q-switch lasers, MOPA architecture allows us to adjust pulse duration, repetition rate and power independently. Beam quality is nearly diffraction limited, and the typical M2 value is1.5. The system is an all-fiber one where the maximum pulse energy achieved at 100 kHz repetition rate is 0.6 mJ and minimum pulse duration is ~30 ns at this energy level. Due to multi-stage architecture and special precautions, the system works without a high amplified spontaneous emission (ASE) level and shows an optical efficiency of 76%. After development of the laser amplifier, and certification of its materials processing capability, an industrial prototype was configured by taking the cost-efficiency into account . The laser components were placed into a compact case which has a simple design for thermal cooling. The developed industrial laser amplifier prototype has several unique properties with respect to other equivalent MOPA design fiber lasers. In material processing, high stability and high beam quality lead to high consistency. Reduced diameters of active and passive fiber cores and specially optimized fiber splices, which are used in the system architecture, result with higher beam quality thus the focusing is superior to many contemporary commercial lasers. As the intensity (areal power density) is the physical quantity that drives the nature of interaction of laser output with materials, the developed system offers long operation life-time due to its capability of operation at lower power levels than its contemporaries. In order to demonstrate the efficiency and the ability of processing various different kinds of materials with the developed laser amplifier system, a multitude of processing applications such as micro drilling, solar cell edge isolation, deep engraving and color marking were tested on metal, semiconductor and insulator surfaces and the results are discussing in relationship with various system operation parameters.M.S. - Master of Scienc
Deneysel1064nm ve 1550nm dalga boyunda çalışan lazer darbe radar-lidar-sisteminin kurulması.
No full textDeneysel1064nm ve 1550nm dalga boyunda çalışan lazer darbe radar-lidar-sisteminin kurulması
Varying Temperature Surface Reflection and its Effect on the Indoor Terahertz Wireless Communications
No full textAdvances in the wireless cellular and network applications also necessitate increased traffic on the communications infrastructure. In order to overcome the capacity overload of the current spectral provisions, service providers are looking at higher frequencies. E and V bands of the millimetre wave spectrum are being utilized for mile range relay links, and higher frequency bands such as 220GHz and 340 GHz regions are being considered for indoor very high data rate applications [1]. A major conundrum in front of indoor Terahertz wireless networking is the effect of the surface reflection: which may be a positive in terms of wider area coverage, and also may be a handicap due to low penetration depths through doors, panels, and such. Indoor surfaces have many different types and textures, and a parameter which may well alter surface reflection coefficients is the varying temperature. Indoor temperature variations are not extreme as the outdoor conditions, yet differentials in excess of 15° to 20° Celcius are normal for most climates throughout seasons. In this work the effect of the varying temperature surface reflections on the communication signal quality of very high data rate (>1Gb/s) data carrying indoor millimetre wave (>100GHz) transmission is studied. It is observed that data transmission quality is more easily affected by the temperature dependant surface reflections compared to conventional reflection power measurements. Various surfaces such as clear and coated drywall, wood panelling, and plastic materials are investigated. In future work, texture roughness and temperature variation will be explored
Inter-satellite optical communication networks: RF fading diversity for higher spectral efficiency
No full textRevolutionary developments in semiconductors lead to efficient deployment of lasers and photodetectors, thus enabling optical transmission of data signals, whether in fiber optic links or free space. Line of sight transmission characteristic of optics ensures the security of the data. With the incessant increase in the numbers of satellites and the data payload required to handle, it is inevitable that in the future we will see a shift towards optical networking, especially in the earth orbiting satellites. We demonstrate a novel all-optical multiplexing technique for doubling the usable spectral bandwidth and number of channels in subcarrier-modulated data transmission over free-space optical connections. By taking advantage of the chromatic-dispersion-induced RF power fading of a given subcarrier frequency, we can transmit two subcarrier channels that occupy the same frequency space.. We successfully transmit and receive two 155 Mbit/s data channels that are both located at 7.1 GHz
Production of v-band straight waveguides with three-dimensional printer and examining of their conductivity
Full text linkBu çalışmada, ticari olarak temin edilebilen standart dikdörtgen dalga kılavuzları (DDK) üç boyutlu (3B) yazıcı kullanılarak üretilmiştir. Bu üretim, diğer literatürden yer alan çalışmalarından farklı olarak V bantta kullanılmak üzere gerçekleştirilmiş ve iletkenliği incelenmiştir. Geleneksel yöntemlerle üretilen milimetre (mm) dalga uygulama ekipmanlarının artan fiyat ve teslim süresi, bu tür ürünlerin mümkün olduğunca kolay ve ucuz üretilmesi ihtiyacını doğurmuştur. Dalga kılavuzları (DK) elektromanyetik dalgaları belirli bir frekans aralığında istenilen bir yönde bir noktadan diğer bir noktaya taşımak için kullanılan pasif elemanlardır. TE10 modunda DDK SolidWorks programı kullanılarak tasarlanmış ve daha sonra eriyik yığma modelleme yöntemi ile PLA termoplastiği kullanılarak üretilmiştir. DK’ların iç yüzeyi kaplandıktan sonra performansı oluşturulan mm-dalga sistemi üzerinde test edilmiştir. Milimetre dalga sisteminde bileşenlerin performansı olarak zayıflama kaybı (S21) ölçülmüştür ve sonuç olarak DDK’ların 1 dB’den daha az zayıflama kaybı olduğu görülmektedir. Bu çalışmada mm-dalga uygulama bileşenlerinin 3B yazıcı ve iletken gümüş boya kullanarak daha ucuz ve hızlı bir şekilde üretilebildiği ortaya konulmuştur.In this work standart rectangular straight waveguides which were obtained commercially are manufactured using three dimensional (3D) printer. Unlike other literature studies, this production was carried out for using in V-band and its conductivity was examined. Increasing cost and delivery time of the traditionally manufactured milimeter (mm) wave application components lead to the requirement of producing this type of products as easy and cheap as possible. Waveguides are passive components that are used to carry the magnetic wave from one point to another point in the desired direction in a certain frequency range. For TE10 mode, rectangular waveguides have been designed with the SolidWorks program and then manufactured using PLA thermoplastics with the fused deposition modelling method. After the inner surfaces of the waveguides are completely covered with silver conductive paint, their performances are tested on the mm wave testpad. The performance of components on the mm-wave system has been measured by obtaining attenuation loss (S21) and as a result, it is seen that straight rectangular waveguides have an attenuation loss of less than 1 dB. It is demonstrated that mm wave application components can be produced with 3D printer cheaper and faster and examined of the conductivities
Varying Temperature Surface Reflection and its Effect on the Indoor Terahertz Wireless Communications
No full textSimulation of locating buried objects via fringe pattern-based measurements in an optical fiber sensor-integrated continuous-wave ground-penetrating radar system
No full textA new ground-penetrating radar system that can determine the depth and position of a buried metal cylinder, which is the combination of an optical fiber sensor (OFS), continuous-wave transmitter, and optical communication link, is proposed and simulated in the MATLAB and Optiwave program packages. Employing an optical sensor instead of a standard radio frequency (RF) receiver offers the advantage of preventing electromagnetic interference along the sensor's main unit cable and lower amplification noise. In this paper, the electric field distribution at the OFS due to reflections from the soil surface and the buried object is obtained mathematically using Green's function. The OFS's detected electric signal is then simulated. The effects of the cylinder's depth and the RF transmitter frequency are observed. The plots of the OFS output voltages vs. the x-axis distance to the burial point display interference fringe patterns. The position and the depth of the cylinder are determined using the characteristics of these patterns. It is estimated that the burial depth can be ascertained with a maximum 5-cm error for a 1-GHz transmitter frequency
Characterization of a Glow Discharge Detector with Terahertz Time Domain Spectroscopy
No full textThe capability of low cost glow discharge detectors (GDDs) for detection of terahertz (THz) radiation draws attention recently. In order to employ them in applications such as THz imaging these studies have typically focused on the response of the GDD at specific frequencies. To better understand the spectral behavior of glow discharges, we have not only examined the response of the GDD at a specific frequency of 118 GHz, but also we examined the interaction mechanism of GDDs with THz radiation using terahertz time domain spectroscopy (THz-TDS) in a broader range of frequencies between 0.05 THz - 0.5 THz
- …
