Dissertations / Theses on the topic 'Optical'
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Hrůza, Libor. "Koherentní analogové zpracování optické informace." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217466.
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In my essay I show Fourier transform theory and applications in context with difraction theory especially Fraunhofer difraction. In part of the experiment, I set up an optical signal processing system. I take the Fourier transform of an input signal using a lens, filter the transform by placing various filters at the Fourier plane, and take the inverse transform. A simple optical bench consists of a laser, to produce a parallel, monochromatic beam which illuminates a specific area of the micrograph. Lens to focus the Fraunhofer diffraction pattern in the back focal plane of the lens. Mask transit contrived light or block out most of the noise in the diffraction pattern arising from image features. A reconstruction lens, placed behind the mask, refocuses the unobstructed rays and forms a filtered image. Optical diffraction provides useful information about the geometrical arrangement of subunits in the specimen. I make experiments for attestation on elementary objects and real images in mathematic program Matlab. From knowledge Fraunhofer difraction and organization of experiment I calculated size of circular object. I show practical using of Fraunhofer difraction and optical filtration. My essay give good introduction to the theory and techniques of optical filtration.
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Filip, Tomáš. "Model optické sítě pro vysokorychlostní datové přenosy." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219446.
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The main goal of this diploma thesis is to design of high-speed optical network. The first part deals with theoretical knowledge in the field of optical transmissions, especially principle of wavelength division multiplexing. Generally speaking, this part is dedicated to optical connections over long distances. It will concentrate on different types of wavelength division multiplexing, optical fiber amplifiers and other basic optical components. Then it discusses influence of negative effects acting on optical transmission and discusses how to reduce or suppress their influence. Subsequently, there is designed backbone network in the Czech Republic in OptiSystem 7.0 software and are verified some mentioned theoretical knowledge. One of chapters also presents results of measurements of real optical routes in our state. The second part of the diploma thesis moves its attention on that part of optical network, which provides data connectivity to end users, that means it is focused on optical access network. There are described the most common topologies, standards and components. Based on these findings, in the last chapter, there is worked out design of optical access network FTTH (more precisely FTTD) in the selected location. Afterwards, the design is transferred to the OptiSystem 7.0 software, where is verified its functionality.
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Křivák, Petr. "Optické bezkabelové spoje s velkým dosahem." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233453.
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This dissertation thesis deals with a long range free space optical links for communication over the distance of few tens of kilometers in the atmosphere. The problematic of the beam propagation and atmospheric effects influencing the beam and the quality of the communication protocol are discussed. The measuring link is also designed to study the parameters of the communication link work conditions. The measuring link consists of two heads. The transmitter head is designed to use two optical beams with laser diodes at the wavelength of the atmospheric windows 850 or 1550 nm and the overall power of hundredths of mW. The receiver head includes the Fressnel lens. For the detection of very weak signal, the avalanche photodiode is used. In the end of this work, due to the high power of the transmitting optical beam, the laser safety conditions are also discussed, including the deduced optical transmitters construction recommendations.
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Stibůrek, Miroslav. "Miniaturní optovláknový senzor teploty pro magnetickou rezonanci." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-401006.
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The following work deals with basics of fiber optics, history of fiber optics, and methods of measuring physical quantities with the use of fiber optic sensors. The work includes facts about physics, chemistry and biology - these elements are necessary for a full understanding of the issue. In order to create an optical fiber temperature sensor based on Fabry Perot resonator principle, several methods of manufacturing the optical cavity are investigated. A practical part of paper consist in the manufacturing of the miniature fiber thermometer, its coating and testing.
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Vettenburg, Tom. "Optimal design of hybrid optical digital imaging systems." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2438.
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Several types of pupil modulation have been reported to decrease the aberration variance of the modulation-transfer-function (MTF) in aberration-tolerant hybrid optical-digital imaging systems. It is common to enforce restorability constraints on the MTF, requiring trade of aberration-tolerance and noise-gain. In this thesis, instead of optimising specific MTF characteristics, the expected imaging-error of the joint design is minimised directly. This method is used to compare commonly used phase-modulation functions. The analysis shows how optimal imaging performance is obtained using moderate phasemodulation, and more importantly, it shows the relative merits of different functions. It is shown that the technique is readily integrable with off-the-shelf optical design software, which is demonstrated with the optimisation of a wide-angle reflective system with significant off-axis aberrations. The imaging error can also be minimised for amplitudeonly masks. It is shown that phase aberrations in an imaging system can be mitigated using binary amplitude masks. This offers a low-cost, transmission-mode alternative to phase correction as used in active and adaptive optics. More efficient masks can be obtained by the optimisation of the imaging fidelity.
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Hampl, Martin. "Prostorové dělení optických svazků." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233502.
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The dissertation thesis deals with a free space optical links, especially is focused directly to the transmission optical beams. The influence of environmental conditions like atmospheric turbulence, buildings movement and vibration is described. As a possibility to reduce these undesirable influences, the generation of the transmission beam by the help of the two-mode optical fiber is proposed. A possibility to drive the shape of the resulting transmission beam by means of the change of power ration of individual modes in fiber is described. The coherence features of the proposed beam are analyzed considering the possibility to reduce the influence of atmospheric turbulence. In the thesis there are introduced beam quality parameters that enable to evaluate the quality of the optical beam for the free space optical link. These parameters give the relationship between the shape of the optical beam and the power balance of the optical link and the statistical evaluation of the optical link.
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Aladeloba, Abisayo Olufemi. "Optically amplified free-space optical communication systems." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13304/.
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This thesis investigates terrestrial atmospheric FSO communication systems operating under the influence of turbulence-induced scintillation, beam spreading, optical interchannel crosstalk, amplified spontaneous emission noise and pointing errors. On-off keying-non–return-to-zero (OOK-NRZ) and digital pulse position (DPPM) are the modulation schemes used for the calculations. The possibility of using sophisticated performance evaluation techniques such as moment generating function (MGF)-based Chernoff bound (CB), modified Chernoff bound (MCB) and saddlepoint approximation (SPA) for terrestrial DPPM and OOK-NRZ–based FSO communication systems employing optical amplification are investigated and compared with the conventional Gaussian approximation (GA) method. Relative to the other techniques, the MCB can be considered a safe estimation method for practical systems since it provides an upper bound upon the BER. The turbulent optically preamplified DPPM FSO receiver employing integration over a time slot and comparing the results to choose the largest slot, is seen to give better advantage (about 7 - 9 dB) compared to an equivalent employing OOK-NRZ signalling. The atmospheric turbulence-induced spreading of the beam, ASE noise, and pointing error are seen to combine in a problematic way resulting in high BERs, depending on the size of the receiver and the beam’s jitter standard deviation. Using FSO communication for the distribution links of a passive optical network-like wavelength division multiplexing access network is investigated in the presence of atmospheric turbulence, ASE noise and interchannel crosstalk. The results show that, for clear atmosphere, FSO distribution link length up to 2000 m can be reliably used (depending on turbulence strength) to achieve human eye safety and high capacity access networks. Also, error floors occur due to turbulence accentuated crosstalk effect for the cases of (i) signal turbulent, but crosstalk not and (ii) crosstalk turbulent, but signal not.
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Liu, Jingjing. "Optically powered transceiver for optical wireless communications." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509980.
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Kubica, Matěj. "Optický polygon." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442372.
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Diploma thesis focuses on a problematics of an optical networks in terms of an optical cables laying and a work with individual fibers. Thesis contains an basic physical properties which are used in a fiber optics. Methodology of correct working procedures used in fiber optics is discussed at the same time. Thesis also contains detailed documentation of realized optical connections including scheme of realized outdoor connection. 3D design of an rack case is also part of the thesis. Rack case provides an option to simulate plenty of different lengths of optical routes. Rack case is designed in 6U variant.
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Hao, Miin-Jong. "Performance evaluation of practival FSK, CPFSK, and ASK detection schemes for coherent optical fiber communication systems." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15686.
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Parker, Matthew. "Optical Tamm states for novel optical and quantum optical devices." Thesis, University of Bristol, 2019. http://hdl.handle.net/1983/111ef532-59fa-49f6-a770-acb3003caf7f.
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The growth in demand for bright, efficient and solid state single-photon sources (SPSs) over the last decades has occurred concurrently with the appearance of quantum information applications that employ the quantized nature of photons. This has led to the development of innovative and complex photonic structures that seek to maximize the quality (Q) factor and coupling rate between a single-emitter (such as quantum dots) and a collectible mode. In this thesis I propose that optical Tamm states, an analogue to the electronic Tamm surface states that occur where a periodic material is terminated at an interface, are a potential alternative to these structures for SPSs and other optical devices. Tamm plasmons (TPs), which occur at the interface of a Bragg mirror and metal layer, has the further attraction that confinement can be added by changing the dimensions of the metal layer. In this thesis I will demonstrate the first measured interaction of quantum dots (QDs) within a confined TP (CTP) at 1.3 um. A simulation study is used to explore their mode behaviour as a function of various parameters, such as metal layer thickness and shape, and the tolerance to emitter position within the mode. New physical phenomena and insights into the effect on collection efficiency are demonstrated, as is a general method for optimizing efficiency of low Q photonic structures, such as confined TPs and low Q micropillars, for SPSs. Finally, these structures are fabricated and characterized. The photoluminescence collected through the top of the device is shown to increase by at least an order of magnitude compared to when the metal layer is absent, showing QD coupling to the mode. This effect is successfully utilized to make CTP photodetectors. These results demonstrate that CTPs are suitable modes for making scalable SPSs.
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Agnew, Amalia. "Quantum-Chemical Investigations of Second- and Third-Order Nonlinear Optical Chromophores for Electro-Optic and All-Optical Switching Applications." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11575.
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The past decades have witnessed the development of new materials with large nonlinear optical properties, which have made them attractive candidats for a broad spectrum of breakthrough applications in the electro-optic and photonic fields (e.g., telecommunication and computing). A deeper understanding of the relationship between, on the one hand, the chemical structure and, on the other hand, the electronic and (linear and nonlinear) optical properties has proven useful for the rational design of new efficient materials. Reaching such an understanding has attracted major interest in the scientific community worldwide in both academia and industry. Therefore, the development of new efficient NLO chromophores and materials along with commercial devices of high quality is helped via the establishment of multidisciplinary research teams combining: (i) the theoretical modeling using quantum-chemical computational calculations; (ii) the organic synthesis; (iii) the optical characterization; and (iv) the device fabrication. In this dissertation, quantum-chemistry is used to evaluate the second- and third-order NLO properties of series of new chromophores and take advantage of a feedback loop with the experimental team to understand the structure-property relationships.
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Baker, Stephen. "Optimal determination of the optical coefficients from scattering media." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268794.
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Geykhman, Roman. "Optimal placement of binary actuators in deformable optical systems." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67794.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 111-113).
Recently, exploration has been conducted into the applicability of binary mechatronics to active figure correction in large optical systems such as space telescopes and ground-based solar-thermal concentrators. This Thesis will continue this exploration. The information-theoretic requirements of the corrective commands required in active optics will be explored to understand the dimensionality of the continuous workspace sampled by binary actuation. In both the minimal expected error and the minimal computation time sense, the optimal discrete workspace is the uniform discrete distribution. A rigorous analogy between binary mechatronics and discrete random variables will be used to show that this optimal workspace is achievable by a linear superposition of actuators with exponentially decreasing influences on the optical surface. It will be proven that elasticity can be exploited to construct mechanisms where constant magnitude actuators exhibit exponentially decaying influences on certain parts of the mechanism, allowing for designs where individual binary actuators correspond to binary bits of the required deformation. A planar truss mechanism designed with this philosophy will be presented and shown to have independent kinematic control of multiple adjacent displacements on its top side. Finally, this design will be shown extend to three dimensions in a manner applicable to optical figure correction. Due to the complexity of mechanisms that meet the optimality criteria, only theoretical analysis will be presented.
by Roman Geykhman.
S.M.
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Valle, Brent. "Design of Multilayer Optical Media: Organic Photovoltaics and Optical Data Storage." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1364917393.
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Takayanagi, Jun, Norihiko Nishizawa, Hiroyuki Nagai, Makoto Yoshida, and Toshio Goto. "Generation of high-power femtosecond pulse and octave-spanning ultrabroad supercontinuum using all-fiber system." IEEE, 2005. http://hdl.handle.net/2237/6770.
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Ji, Zheng. "The Use of Optical Metrology in Active Positioning of a Lens." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699892/.
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Precisely positioned optical lenses are currently required for many highly repetitive mechanics and applications. Thus the need for micron-scale repetition between opto-mechanical units is evident, especially in industrial manufacturing and medical breakthroughs. In this thesis, a novel optical metrology system is proposed, designed, and built whose purpose is to precisely locate the center of a mechanical fixture and then to assemble a plano-convex optical lens into the located position of the fixture. Center location specifications up to ±3 µm decenter and ±0.001° tilting accuracy are required. Nine precisely positioned lenses and fixtures were built with eight units passing the requirements with a repetitive standard deviation of ±0.15 µm or less. The assembled units show satisfactory results.
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Maleev, Ivan. "Partial coherence and optical vortices." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0713104-021808/.
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Simpson, Neil B. "Optical spanners and improved optical tweezers." Thesis, University of St Andrews, 1998. http://hdl.handle.net/10023/14884.
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This thesis describes the experimental and theoretical work that investigated the transfer of orbital angular momentum from light to matter. This was achieved by combining two established areas of laser physics which were "optical tweezers" and Laguerre-Gaussian laser modes. The optical tweezers are essentially a tightly focussed laser beam from a high numerical aperture microscope objective lens, which traps particles in three dimensions just below the beam focus. By incorporating a Laguerre- Gaussian laser mode into the tweezers system, the trapping efficiency was doubled. These improved optical tweezers have been successfully demonstrated both theoretically and experimentally. In addition to the spin angular momentum which is associated with the polarisation state, the Laguerre-Gaussian laser modes also possess orbital angular momentum. The "optical spanners" utilised this property by transferring orbital angular momentum from the laser beam to the trapped particle, causing it to rotate whilst being held in the optical trap. This effect was theoretically modelled and experimentally observed. Using the optical spanners, the spin angular momentum of the laser was used to directly cancel the orbital angular momentum in the beam, which was observed as a cessation in rotation of the trapped particle. This demonstrated the mechanical equivalence of the spin and orbital components of angular momentum in a light beam, and gave experimental evidence for the well defined nature of the orbital angular momentum present in Laguerre-Gaussian laser modes.
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BOSCO, ALESSIO. "All-Optical Processing by Second Order Nonlinearities." Doctoral thesis, La Sapienza, 2005. http://hdl.handle.net/11573/916893.
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Diamond, Cornelius. "OMOS : optically written micro-optical systems in photopolymer /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9963665.
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Balon, Jiří. "Měřící metody klíčových parametrů v optických sítích." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218247.
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The main goal of the master’s thesis was to familiarize with optical networks dilemma and its measuring during fabrication. The whole thesis is divided into several parts where the first part deals with optic fiber dilemma. It describes its kinds, properties and also suggests a basic principle of optic signal dispersion using these fibers. It describes also optical network FTTx architecture (Fiber To The x). The second part of the thesis focuses on methods of measuring key parameters of optical networks. Is brings out the methods of measuring optical loss and dispersive influences. The last and final part in focused on creating a methodical manual for measuring these networks during its fabrication and verifying measuring methods stated in the theoretical part inside a real network. Measuring was implemented on an optical network of Masaryk University in Brno.
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Hašek, Jaroslav. "Laserový vysílač s optickým vláknem." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217799.
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This master´s thesis deals with communication which is provided by optical devices. Optical wireless links are enforced due to high bit rate, responsibility and noise immunity. Main part of this master´s project is devoted to optical fibre, its characteristic and its usage in laser transmitter.
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Wang, Lon A. "Optical computing using interference filters as nonlinear optical logic gates and holographic optical elements as optical interconnects." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184502.
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This dissertation experimentally explores digital optical computing and optical interconnects with theoretical supports, from the physics of materials and the optimization of devices to system realization. The trend of optical computing is highlighted with the emphasis on the current development of its basic constituent elements, and a couple of algorithms selected to pave the way for utilizing bistable devices for their optical implementations. Optical bistable devices function as "optical transistors" in optical computing. The physics of dispersive optical bistability is briefly described. Bistable ZnS interference filters are discussed in detail regarding their linear and nonlienar characteristics. The optimization of switching characteristics for a bistable ZnS interference filter is discussed, and experimental results are shown. Symbolic substitution which fully takes advantage of regular optical interconnects constitutes two steps: pattern recognition and symbol scription. Two experiments on two digital pattern recognitions and one on a simple but complete symbolic substitution have been demonstrated. The extension of these experiments is an implementation of a binary adder. A one-bit full adder which is a basic block for a computer has been explored experimentally and demonstrated in an all-optical way. The utilization of a bistable device as a nonlinear decision-making element is further demonstrated in an associative memory experiment by incorporating a Vander Lugt matched filter to discriminate two partial fingerprints. The thresholding function of a bistable device enhances the S/N ratio and helps discrimination in associative memory. As the clocking speed of a computer goes higher, e.g. greater than several GHz, the clock signal distribution and packaging become serious problems in VLSI technology. The use of optical interconnects introduces a possible solution. A unique element for holographic optical interconnects, which combines advantages of computer generated hologram and DCG recording material, is discussed. Pattern design of a specific computer generated hologram and a proposed fabrication process are described. Experimental results suggest that this unique element has the capability of being tailored to perform multiple fan-out with resulting uniform tightly-focussed spots, and coupling between devices, e.g. source-to-fiber and fiber-to-waveguides, etc.
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Semenets, V. V., M. V. Neofitnyy, Yu P. Machekhin, O. S. Hnatenko, V. I. Zarytskyi, and S. V. Gulak. "Laser system for recording optics." Thesis, CAOL, 2019. http://openarchive.nure.ua/handle/document/15098.
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The development of a modern laser system for recording optics is presented in this research paper. Studying optical components for designing this system by various methods, by calculated methods and by a method of using modern modeling package Zemax, was conducted. The results of the calculations and simulation, which led to the preliminary design of the laser system of optics registration, coincide.
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Park, Seung-Han. "Excitonic optical nonlinearities in semiconductors and semiconductor microstructures." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184551.
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This dissertation describes the study of excitonic optical nonlinearities in semiconductors and semiconductor microstructures. The main emphasis is placed on the evolution of optical nonlinearities as one goes from bulk to quantum-confined structures. Included are experimental studies of molecular-beam-epitaxially-grown bulk GaAs and ZnSe, GaAs/AlGaAs multiple-Quantum-Wells (MQW's), and finally, quantum-confined CdSe-doped glasses. The microscopic origins and magnitudes of the optical nonlinearities of bulk GaAs and ZnSe were investigated and the exciton recovery time in ZnSe was measured. A comparison with a plasma theory indicates that in GaAs, band filling and screening of the continuum-state Coulomb enhancement are the most efficient mechanisms, while in ZnSe, exciton screening and broadening are the dominating mechanism for the nonlinearity. The maximum nonlinear index per excited electron-hole pair of ZnSe at room temperature is comparable to that of bulk GaAs and the exciton recovery times are of the order of 100 ps or less. A systematic study of the dependence of the optical nonlinearities on quantum well thickness for GaAs/AlGaAs MQWs and the results of nonlinear optical switching and gain in a 58 A GaAs/AlGaAs MQW are reported and discussed. The maximum change in the refractive index is greatest for the MQWs with the smallest well size and decreases with increasing well size, reaching a minimum for bulk GaAs. The maximum index change per photoexcited carrier increases by a factor of 3 as the well size decreases from bulk to 76 A MQW. A differential energy gain of 0.2 and the contrast of 4 are measured for a 58 MQW using 3 ns laser pulses. The linear and nonlinear optical properties of CdSe semiconductor microcrystallites grown under different heat treatments in borosilicate glasses are investigated. Pump-probe spectroscopic techniques and interferometric techniques were employed to study size quantization effects in these microcrystallites (quantum dots). Nonlinear optical properties due to the transitions between quantum confined electron and hole states are reported for low temperature and room temperature. A relatively large homogeneous linewidth is observed. Single beam saturation experiments for quantum confined samples were performed to study the optical nonlinearities as a function of microcrystallite size. Results indicate that the saturation intensity is larger for smaller size quantum dots.
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Fragemann, Anna. "Optical parametric amplification with periodically poled KTiOPO4." Doctoral thesis, KTH, Laserfysik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-531.
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This thesis explores the use of engineered nonlinear crystals from the KTiOPO4 (KTP) family as the gain material in optical parametric amplifiers (OPAs), with the aim to achieve more knowledge about the benefits and limitations of these devices. The work aims further at extending the possible applications of OPAs by constructing and investigating several efficient and well performing amplifiers. An OPA consists of a strong pump source, which transfers its energy to a weak seed beam while propagating through a nonlinear crystal. The crystals employed in this work are members of the KTP family, which are attractive due to their large nonlinear coefficients, high resistance to damage and wide transparency range. The flexibility of OPAs with respect to different wavelength regions and pulse regimes was examined by employing various dissimilar seed and pump sources. The possibility to adapt an OPA to a specific pump and seed wavelength and achieve efficient energy conversion between the beams, originates from quasi-phasematching, which is achieved in periodically poled (PP) nonlinear crystals. Quasi-phasematched samples can be obtained by changing the position of certain atoms in a ferroelectric crystal and thereby reversing the spontaneous polarisation. In this thesis several material properties of PP crystals from the KTP family were examined. The wavelength and temperature dispersion of the refractive index were determined for PP RbTiOPO4, which is essential for future use of this material. Another experiment helped to increase the insight into the volumes close to domain walls in PP crystals Further, several OPAs were built and their ability to efficiently amplify the seed beam without changing its spectral or spatial properties was studied. Small signal gains of up to 55 dB and conversion efficiencies of more than 35 % were achieved for single pass arrangements employing 8 mm long PPKTP crystals. Apart from constructing three setups, which generated powerful nanosecond, picosecond and femtosecond pulses, the possibility to amplify broadband signals was investigated. An increase of the OPA bandwidth by a factor of approximately three was achieved in a noncollinear configuration.QC 20101013
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An, Dechang. "Electro-optic polymer-based monolithic waveguide devices with multi-functions of amplification switching and modulation." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035933.
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Atabaki, Amir Hossein. "Reconfigurable silicon photonic devices for optical signal processing." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41207.
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Processing of high-speed data using optical signals is a promising approach for tackling the bandwidth and speed challenges of today's electronics. Realization of complex optical signal processing functionalities seems more possible than any time before, thanks to the recent achievements in silicon photonics towards large-scale photonic integration. In this Ph.D. work, a novel thermal reconfiguration technology is proposed and experimentally demonstrated for silicon photonics that is compact, low-loss, low-power, fast, with a large tuning-range. These properties are all required for large-scale optical signal processing and had not been simultaneously achieved in a single device technology prior to this work. This device technology is applied to a new class of resonator-based devices for reconfigurable nonlinear optical signal processing. For the first time, we have demonstrated the possibility of resonance wavelength tuning of individual resonances and their coupling coefficients. Using this new device concept, we have demonstrated tunable wavelength-conversion through four-wave mixing in a resonator-based silicon device for the first time.
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Yazdani, Arash. "Contributions to optimal detection in OTDM and OCDMA optical receivers." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/398408.
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Recent developments in optical communication systems have increased the performance of optical networks. Low attenuation fiber optics, high spectral purity lasers and optical amplifiers, among others, are systems that have allowed to transport terabits per second across thousands of kilometers, in a more reliable, secure and efficient manner, compared to radiofrequency (RF) systems. New optical access network technologies such as EPON and GPON are also providing Gbit/s connectivity to customers in both the enterprise and consumer markets. This transport capacity provides enough data for the growing demand of new communication services.
The main goal of the researchers in optical networks is to provide higher-speed data transmission by exploiting the intrinsically fast behavior of the optical domain. Optical signal processing is a key technology for constructing flexible and ultra high-speed photonic networks. In this context, it will be possible to build ultra-high speed, simple and reliable optical networks, at low operational expenses, regardless of the format of the information.
Before these technologies enter into commercial operation, some obstacles should be removed, such as the problem of obtaining extremely precise synchronization of the network without any optical-electrical conversion. Also, a synchronization-related problem appear at the receiver for some systems such as OTDM and OCDMA, where even the fastest photo-detectors are not able to separate the data of the desired user from the signals of the adjacent users. This means that detection of ultrashort pulses in the presence of the multiple access interference (MAI) is key in these systems. Therefore, it is vital to apply an all-optical signal processing on the received optical signal before the photo-detection. In most of the ultra-high-speed light-wave communication systems, it is an effective technique to use an optical time gating at the receiver side in order to extract the desired user's signal from the received signal. This approach requires an optical clock recovery procedure. But by increasing the data rate in optical networks the accuracy of the optical clock recovery decreases because of increasing jitter and MAI and consequently the system performance is degraded. Currently the only approach is to use a clock signal that has the same pulse-width as the data, and when the jitter is large, this technique fails to properly capture the main part of the data signal and collects more interference instead, so these techniques have to lower the data-rate to avoid large BERs. Our contributions can achieve larger signal to noise ratio versus the fixed pulse-width clock.
The main goal of this work is to discuss the characteristics of the current transmission technologies, including OTDM and OCDMA, providing a detailed analytical model and proposing a solution for improving the performance of optical receivers. We use a nonlinear media (Four Wave Mixing) as a combiner in the receivers. We have modeled analytically the relationship between the input and the output of the nonlinear media systems in these techniques using nonlinear Schrödinger equations. Then, we solved these equations by Volterra series. Our aim is to develop analytical models of the response of the optical receiver, and validate them with simulations. Also we consider the effect of variation of the bandwidth of the clock in the performance of receivers with presence of jitter. We obtain the optimum value of the clock's bandwidth and confirm that theory and simulation results coincide. Using our proposed technique, the data-rate of the optical systems can be increased and we can achieve a lower BER for the same jitter. The goal of these efforts is the improvement of the overall performance of the network, in terms of transmission speed, bit error rate (BER), reliability and cost. The results could be applied to next-generation optical networks, in both the backbone and access scenarios.Los sistemas de comunicaciones ópticas aumentan constantemente su rendimiento. La disponibilidad de fibras con muy baja atenuación, láseres de alta pureza espectral y amplificadores ópticos, entre otros, hacen factible el transporte de Tbit/s a miles de kilómetros, de una manera más fiable, segura y eficiente que los sistemas basados en radiofrecuencia. Una nueva generación de redes ópticas de acceso, tales como EPON y GPON, ya están proporcionando conectividad a Gbit/s en los mercados tanto empresarial y de consumo, lo que permitirá sostener la creciente demanda de los usuarios. El principal objetivo de los investigadores en el campo de las redes ópticas es aumentar la velocidad de transmisión de datos, explotando el comportamiento intrínsecamente rápido del dominio óptico. En este contexto, el procesado de la señal en el dominio óptico es una tecnología clave para la construcción de redes fotónicas manteniendo su simplicidad y el bajo coste de operación, así como la independencia del formato de la información. Para conseguirlo, hay obstáculos a superar, como el problema del mantenimiento de la sincronía extremadamente precisa que es necesaria en redes sin conversión electro-óptica. Otro problema es la recuperación de la sincronía en los detectores de los receptores usados en las técnicas OTDM y OCDMA, donde incluso los fotodetectores más rápidos no son capaces de separar los datos del usuario deseado de las señales de los usuarios adyacentes. La detección de pulsos ultracortos en presencia de la interferencia debida al acceso múltiple (MAI) es un reto importante. Por ello es vital aplicar procesado óptico en la señal recibida, antes de la fotodetección. Una técnica efectiva para realizar la detección es el uso de una puerta óptica en el receptor, con el fin de extraer la señal del usuario deseado. Esto requiere recuperar por procedimientos puramente ópticos la señal de reloj. Pero al aumentar la velocidad de transmisión, la precisión de la recuperación de reloj disminuye debido al aumento de la fluctuación de fase (jitter) y la MAI, y en consecuencia el rendimiento del sistema se degrada. Actualmente, el enfoque usado es usar un reloj con el mismo ancho de pulso que la señal de datos útiles, pero cuando la fluctuación de fase es grande, esta técnica falla al no capturar correctamente la parte principal de la señal de datos y recoger una mayor interferencia. Forzando estas técnicas a trabajar a velocidades inferiores a las potenciales para evitar que la tasa de errores (BER) se dispare. Este trabajo logra una mayor relación señal a ruido (y por tanto, una BER inferior) respecto el caso de las señales con duración fija del pulso de reloj. Se han analizado las características de las tecnologías OTDM y OCDMA, proponiendo un modelo analítico detallado, y se ha aportado una solución para mejorar el rendimiento de los receptores ópticos, utilizando un medio no lineal (Four Wave Mixing) como combinador en los receptores. Se ha modelado analíticamente la relación entre la entrada y la salida en un medio no lineal, mediante técnicas que utilizan las ecuaciones de Schrödinger, solucionadas mediante series de Volterra. Los modelos analiticos de la respuesta del receptor óptico se han validado con simulaciones, teniendo en cuenta el efecto de la variación del ancho de banda del reloj en el rendimiento de los receptores, con presencia de fluctuación de fase. Se ha obtenido el valor óptimo del ancho de banda de la señal de reloj, y se ha comprobado que los resultados de la teoría y la simulación coinciden. Los resultados obtenidos permiten incrementar la velocidad de transmisión de datos en redes ópticas manteniendo la BER, o bien obtener una BER más baja para el mismo nivel de jitter
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Priyadarshi, Sanjay. "Optimal operating conditions and security considerations for optical chaos communications." Thesis, Bangor University, 2013. https://research.bangor.ac.uk/portal/en/theses/optimal-operating-conditions-and-security-considerations-for-optical-chaos-communications(63997d52-0808-47b1-a995-64e4dfebd099).html.
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This thesis details research on chaos-based optical communications using semiconductor lasers. Theoretical work has identified optimal operating condition of optical chaos communications systems without the need for re-adjustment of laser operating conditions in the field. In addition, an experimental investigation has been undertaken of one aspect of the security of message transmission using chaotic semiconductor lasers and specifically using Vertical-Cavity Surface-Emitting Laser (VCSEL). In optical chaos communications a message is masked in the noise-like broadband output of a chaotic transmitter laser, and message recovery is enabled through the synchronization of the transmitter and the (chaotic) receiver laser. Key issues are to identify the laser operating conditions which provide the highest quality synchronization conditions and those which provide optimized message extraction. In general such operating conditions are not coincident. In this thesis numerical simulations are performed with the aim of identifying a regime of operation where the highest quality synchronization and optimizing message extraction efficiency are achieved simultaneously for the analogue and digital message modulation. Use of such an operating regime will facilitate practical deployment of optical chaos communications systems without the need for re-adjustment of laser operating conditions in the field. In this way it has been found, for example, that in an optical chaos communication system an optimal configuration for 1 GHz modulation frequency may utilize a 2% modulation depth and 20% coupling rate from transmitter laser to receiver laser for analogue message modulation. Ideal operating conditions for digital message modulation, identified using the laser bias current as the control parameter, are found for 2GB/s message transmission and a modulation depth of about 2%. An experimental study has also been undertaken to determine the effect of time delay and concealment in the external cavity semiconductor laser systems. The time delay (TD) signature arises due to the external cavity round trip time of feedback in the external cavity semiconductor laser system. The identification of the time delay may affect the security of encoded messages. An external cavity VCSEL with variable optical-polarization-angle feedback has been explored experimentally in order to identify conditions for time delay concealment. In this work the VCSEL was subject not only to variable optical polarization angle of feedback but also variable optical feedback strength and bias current. The TD signature concealment is evaluated through the use of an autocorrelation function and an information theory-based permutation entropy function. It was found that the TD signature is concealed at low feedback strength of order –18 dB. At moderate feedback strengths, the TD signature is sensitive to the rotation of the polarization angle of the optical feedback with TD concealment being observed for polarization angles in the range from 45° to 90°.
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LEE, YONG HEE. "ROOM-TEMPERATURE OPTICAL NONLINEARITIES IN GALLIUM-ARSENIDE AND FAST OPTICAL LOGIC GATES." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183920.
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This dissertation studies the physics of room-temperature optical nonlinearities in GaAs and their application to the optical logic gates. The microscopic origins of the room-temperature optical nonlinearities in GaAs are investigated experimentally and theoretically. The data of nonlinear absorption measurement are analyzed in the framework of a semiconductor plasma theory in combination with excitation-dependent line broadening. The importance of the plasma screening of the continuum-state Coulomb enhancement and band filling are emphasized for GaAs at room temperature. Optical bistability and optical logic gating are direct consequences of the nonlinear refractive index changes in etalons. The nonlinear index changes are directly measured by a new technique of observing the Fabry-Perot transmission peak shift using the self-photoluminescence as a broad-band source. The validity of a Kramers-Kronig technique under quasi-steady state conditions is crosschecked by an independent measurement of Δn under identical pumping conditions. Thermal index changes are also directly measured to establish the criteria on the temperature stability condition that is needed for reliable operation of devices based on dispersive nonlinearities. Optical logic gates based on dispersive optical nonlinearities may be the critical components of an all-optical computer in the future. Five optical logic functions are demonstrated in a nonlinear GaAs/AlGaAs MQW etalon. Specially designed dielectric mirrors are used to observe low-energy (3-pJ) operation of optical logic gates. Parallel operation using as many as eight optical logic devices is achieved with Wollaston prisms. Toward practical devices, optical logic gating using diode lasers is demonstrated in a setup much smaller than the usual argon-laser pumped dye laser setup. The cycle time of optical logic devices is limited, not by the switch-on time, but by the switch-off time which depends on the carrier relaxation rather than the switch-on time. To reduce the carrier relaxation time windowless GaAs is employed to take advantage of the faster surface recombination of carriers at the GaAs/dielectric mirror interface compared to that at the GaAs/GaAlAs interface. The speed and effectiveness of the windowless GaAs are compared with those of the proton-bombarded GaAs as optical logic gates.
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Jedrkiewicz, Ottavia. "Theories of atom-field interaction in cavities and retrodiction for quantum communications." Thesis, University of Essex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340589.
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Haris, Muhammad. "Advanced modulation formats for high-bit-rate optical networks." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24811.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Chang, Gee-Kung; Committee Co-Chair: Yu, Jianjun; Committee Member: Altunbasak, Yucel; Committee Member: Ji, Chunayi; Committee Member: Ralph, Stephen; Committee Member: Xu, Jun.
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Lee, Woei Ming. "Optical trapping : optical interferometric metrology and nanophotonics." Thesis, St Andrews, 2010. http://hdl.handle.net/10023/882.
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Galloway, Peter Colin McLaren. "Holographic optical elements for optical fibre application." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389195.
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Thakulsukannant, Kornkamol. "Advanced optical switching technology for optical networking." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500403.
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Bristow, Julian Paul Gregory. "Integrated optical components for optical fibre sensors." Thesis, University of Glasgow, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329519.
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Head, Christopher Robin. "Optical trapping and optical sources for nanophotonics." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/359888/.
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In this thesis I describe work that I have done in two separate research areas. The first involves optical micro manipulation of nano-scale objects and their orientation. The second concerns the development of a semiconductor laser to provide high beam quality,average and peak power and short pulse durations. Optical tweezers are an excellent tool to manipulate nano scale objects in all three dimensions. An additional degree of control, the rotational alignment of assymetrical particles, is demonstrated by polarisation analysis of two photon induced fluorescence of the trapped and rotated semiconductor nanorods.Mode-locked vertical external-cavity surface emitting lasers (VECSELs) have recently achieved multi-watt average power levels. Nevertheless the need to optimize the gain structure design, in order to consistently obtain sub 200 fs pulse durations, still remains. The evolution of the intra-cavity power build-up transient is utilized for a novel spectro-temporal technique which allows for the extraction of the curvature of the gain spectrum during actual operation and enables the observation of the evolution of the gain spectrum during lasing build-up. In addition a method to obtain the total cavity loss via the combination of the power build-up transient and photo luminescence decline, during lasing onset is shown. The use of an amplified, femtosecond-pulsed and GHz repetition rate VECSEL to generate multi-watt average power supercontinuum in photonic crystal fibres (PCFs) is presented. Supercontinuum generation with GHz pulse repetition rates is of interest for frequency combs as the high repetition rate increases the mode spacing of the comb and energy per mode. Two different PCFs, one with an all-normal dispersion profile and one with a zero dispersion wavelength (ZDW) at 1040 nm, are pumped with the amplified VECSEL pulses generating spectral components over 200 nm and 500 nm, respectively. The thesis concludes with a proposal to use the advantages of both optical tweezers and VECSELs to analyse and resonantly excite the vibrational frequencies of single nano-scale objects.
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McDonald, Mark Edmund. "Optical engineering of parallel optical data storage." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/289037.
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Volume holographic data storage uses the superposition of image holograms in a suitable medium to pursue large storage capacity and high readout rates. The holographic method of structuring the medium with data, and subsequent readout of those data structures, relies on an optical system with two distinct paths. The object path is typically a 4F system relaying a high space-bandwidth-product object to an image plane with the storage medium placed near the Fourier plane. Optical system parallelism, measured by space-bandwidth-produce, promotes both storage capacity and readout rate. The reference path is typically a relay with the field stop placed near the center of the storage material. We will consider how the properties of the object path optical system affect the storage capacity and readout rate. We will demonstrate that the object beam 4F system can be optimized for the particular requirements of volume holographic storage, and that relatively simple optical systems can provide high parallelism. We will also consider the optical parallelism possible for standard optical disk storage, and how these results compare to volume holographic storage. Finally, we will consider how the optical system of the reference path affects the storage capacity. We find that modifications to the reference beam, or apodization, can substantially mitigate the effects of interpage crosstalk, a fundamental noise source in volume holographic storage.
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Le, Dinh Danh. "All-Optical Multicast Routing under Optical Constraints." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS214/document.
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Au cours de la dernière décennie, le trafic dans les réseaux a connu une croissance explosive en double environ tous les trente trois mois. Les sources à l'origine de cette croissance proviennent de nombreuses applications à grande vitesse qui impliquent la transmission de données dans des groupes de multicast. Pour réaliser la multicast optique, les routeurs optiques peuvent avoir des répartiteurs de lumière spéciaux pour diviser des signaux lumineux et des convertisseurs de longueur d'onde pour modifier les longueurs d'onde où c'est nécessaire. Cependant, la division réduit l'énergie du signal qui nécessite alors une amplification ou une régénération qui nécessitent du matériel coûteux. Les convertisseurs de longueurs d'onde aussi ne sont pas suffisamment matures pour être largement déployés dans les technologies optiques actuelles. Par conséquent, dans les réseaux tout-optique, les unités de transformation des routeurs sont souvent hétérogènes et les algorithmes de routage doivent en tenir compte tout en parvenant à des solutions de compromis coût-performances qui satisfassent les exigences de bande passante et les contraintes optiques.Dans cette thèse, nous étudions les problème de routage multicast tout-optique (AOMR) dans les réseaux tout-optique hétérogènes. L'hétérogénéité provient principalement de l'absence / présence de séparateurs de lumière et de convertisseurs de longueur d'onde et de la répartition inégale des longueurs d'onde dans les liens du réseau. En général, les problèmes de AOMR sont NP-difficiles. L'objectif de la thèse est d'analyser et de formuler les problèmes sous différentes contraintes optiques, pour rechercher des solutions optimales ou proposer des heuristiques efficaces. Les deux contextes possibles, la demande unique ou multiple de multicast, sont examinés. Toutes les propositions présentées dans la thèse sont validées par des simulations approfondies. Les principales contributions peuvent être résumées comme il suit.1) Nous identifions les structures des routes optimales pour les problèmes de l'AOMR dans les réseaux WDM hétérogènes. Comme indiqué dans la thèse, les solutions optimales ne sont plus basées sur des arbres de lumière classiques, mais sur une structure arborescente plus générale appelée hiérarchie. Certaines formes de hiérarchie pour la multicast WDM sont des parcours optiques, des hiérarchies optiques, des hiérarchies-araignée optiques ou encore des ensembles de ces routes optiques. Les algorithmes exacts et les heuristiques proposés dans la thèse sont principalement basés sur les hiérarchies.2) Dans le cas du problème de multicast avec une seule demande dans des réseaux partiellement équipés de diviseurs de lumière, nous proposons une heuristique efficace dont les résultats font le compromis entre la consommation de longueur d'onde, le coût total, et le délai de bout-en-bout.3) Dans le même cas mais dans des réseaux non équipés de diviseurs de lumière, nous prouvons la NP-difficulté, exprimons les problèmes au moyen d'un programme linéaire (ILP) pour trouver les solutions exactes et proposons plusieurs heuristiques pour calculer de bonnes solutions.4) Pour le cas de demandes multicast multiples, nous nous concentrons sur les modèles de trafic statiques dans des réseaux partiellement équipés de diviseurs mais sans convertisseurs de longueur d'onde. Tout d'abord nous proposons une formulation ILP sur la base de hiérarchies optiques afin de rechercher la solution optimale. Ensuite, utilisant un modèle de graphe en couches, nous développons plusieurs heuristiques adaptatives pour calculer des hiérarchies optiques de solutions approximatives. Ces algorithmes adaptatifs surpassent les techniques de routage existants pour minimiser la probabilité de blocage.Dans l'ensemble, la thèse souligne que les solutions optimales pour les problèmes de l'AOMR considérés correspondent à des hiérarchies, que ce soit pour une seule demande ou des demandes multiplesOver the past decade, network traffic levels experienced an explosive growth at about double amount in approximately every thirty months. The sources accounting for this growth come from numerous high-speed applications (e.g., video-on-demand, high-definition television) which involve the data transmission in multicast groups. To realize optical multicasting, optical routers should have light splitters to split light signals and wavelength converters to change the wavelengths wherever needed. However, the splitting reduces the energy of the output signal which in turn requires the costly power amplification or regeneration. Wavelength converters are also immature to be deployed widely in current optical technologies. Consequently, in all-optical networks, routers are often heterogeneous in their processing units, which challenges the routing. Therefore, it is crucial to design efficient multicast routing strategies at the backbone optical networks, in order to achieve cost-performance tradeoff solutions while satisfying the ever-increasing bandwidth demands and optical constraints.In this thesis, we investigate the all-optical multicast routing (AOMR) problems in heterogeneous optical networks. The heterogeneity mainly comes from the absence/presence of light splitters and wavelength converters and the uneven distribution of wavelengths in the network links. In general, AOMR problems are often NP-hard. The objective of the thesis is to analyze and formulate the problems, to search for the optimal solutions, and to propose efficient heuristics to solve the problems under different optical constraints. Both possible contexts, i.e., single-multicast request and multiple-multicast requests, are examined. All the reported results in the thesis are supported by extensive and careful simulations. The major contributions can be summarized as follows.1) We identify the optimal route structures for AOMR problems under heterogeneous mesh WDM networks. As shown in the thesis, the optimal solutions are no longer based on conventional light-trees, but a more general tree-like structure called hierarchy. Some forms of hierarchy realized for WDM multicasting are light-trails, light-hierarchies, light-spider hierarchies and a set of these light-structures. The exact and heuristic algorithms proposed in the thesis are mainly based on hierarchy. 2) For single-multicast with sparse-splitting case, we propose an efficient heuristic algorithm to produce a good tradeoff solution among wavelength consumption, channel total cost and end-to-end delay.3) For single-multicast with non-splitting case, we prove the NP-hardness, identify the optimal solution as a set of light-spider hierarchies, formulate the problems by means of Integer Linear Program (ILP) formulations to find the exact solution, and propose several cost-effective heuristic algorithms to compute the approximate solutions. 4) For the case with multiple-multicast requests, we focus on static traffic patterns under sparse-splitting without wavelength conversion case. First, an ILP formulation based on light-hierarchies is proposed to search for the optimal solution. By applying the layered graph model, we then develop several adaptive heuristic algorithms to compute light-hierarchies for approximate solutions. These adaptive algorithms outperform the existing fixed routing ones in minimizing the blocking probability. Overall, the thesis points out that the optimal solutions for heterogeneously constrained AOMR problems correspond to hierarchies, regardless of request multiplicity consideration
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Fragemann, Anna. "Optical parametric amplification with periodically poled KTiOPO4." Doctoral thesis, KTH, Physics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-531.
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This thesis explores the use of engineered nonlinear crystals from the KTiOPO4 (KTP) family as the gain material in optical parametric amplifiers (OPAs), with the aim to achieve more knowledge about the benefits and limitations of these devices. The work aims further at extending the possible applications of OPAs by constructing and investigating several efficient and well performing amplifiers.
An OPA consists of a strong pump source, which transfers its energy to a weak seed beam while propagating through a nonlinear crystal. The crystals employed in this work are members of the KTP family, which are attractive due to their large nonlinear coefficients, high resistance to damage and wide transparency range. The flexibility of OPAs with respect to different wavelength regions and pulse regimes was examined by employing various dissimilar seed and pump sources.
The possibility to adapt an OPA to a specific pump and seed wavelength and achieve efficient energy conversion between the beams, originates from quasi-phasematching, which is achieved in periodically poled (PP) nonlinear crystals. Quasi-phasematched samples can be obtained by changing the position of certain atoms in a ferroelectric crystal and thereby reversing the spontaneous polarisation.
In this thesis several material properties of PP crystals from the KTP family were examined. The wavelength and temperature dispersion of the refractive index were determined for PP RbTiOPO4, which is essential for future use of this material. Another experiment helped to increase the insight into the volumes close to domain walls in PP crystals
Further, several OPAs were built and their ability to efficiently amplify the seed beam without changing its spectral or spatial properties was studied. Small signal gains of up to 55 dB and conversion efficiencies of more than 35 % were achieved for single pass arrangements employing 8 mm long PPKTP crystals. Apart from constructing three setups, which generated powerful nanosecond, picosecond and femtosecond pulses, the possibility to amplify broadband signals was investigated. An increase of the OPA bandwidth by a factor of approximately three was achieved in a noncollinear configuration.
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Pavlů, Michal. "Modelování vícekanálového optického bezkabelového spoje." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219817.
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This thesis deals with multi-channel wireless links with a higher range designated for free-space communications in an atmospheric media. Propagation of the optical beam in an atmosphere is analysed and various influences affecting the quality of the transmitted signal are described. The simulation is carried out for dual optical link. Link budget of individual paths working at the wavelengths in the atmospheric windows – 850 nm and 1550nm. It also examined optical intensity distribution of the transmitted beam. At the end of the work performed measurements and simulations verify the accuracy of the components used in wireless link.
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Zheng, Xing. "Advanced Optical OFDM transceivers for Optical Access Networks." Thesis, Bangor University, 2011. https://research.bangor.ac.uk/portal/en/theses/advanced-optical-ofdm-transceivers-for-optical-access-networks(cdd26537-a8c0-4df1-84e3-7baa55b20fb4).html.
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Intensity Modulation and Direct Detection (IMDD) Optical Orthogonal Frequency Division Multiplexing (OOFDM) is considered as one of the most competitive candidates for high-speed, cost-effective and flexible Next Generation Passive Optical Networks (NGPONs). For practical implementation of the technique, five technical challenges originating from inherent OFDM properties and/or IMDD system characteristics have to be solved successfully. The challenges include: i) insufficient utilization of Multi-Mode Fibre (MMF) frequency response; ii) improvement in IMDD OOFDM transmission capacity in Single- Mode Fibre (SMF)-based systems; iii) simplification of OOFDM transceiver configurations; iv) the employment of low-cost transceiver components to achieve the desired system performance; v) effective compensation of directly modulated DFB laser (DML)-induced positive frequency chirp. The present PhD dissertation research is dedicated to addressing the aforementioned challenges. For fully utilizing the system frequency response of a MMF transmission link, an Adaptively Modulated OOFDM (AMOOFDM) modem using Subcarrier Modulation (SCM) (AMOOFDM-SCM) is proposed, which consists of two AMOOFDM modems in parallel with one operating at the baseband and the other being modulated onto an intermediate Radio Frequency (RF) carrier. Extensive investigations show that, compared with AMOOFDM, AMOOFDM-SCM not only enhances the transmission capacity versus reach performance by a factor of approximately 2, but also considerably improves the system flexibility and performance robustness. When use is made of the AMOOFDM-SCM technique in SMF-based transmission links, the intermixing effect induced by direct detection in the receiver is identified to be a dominant factor limiting the maximum achievable AMOOFDM-SCM performance. To maximize the link performance through mitigating the intermixing effect, three AMOOFDM-SCM modem designs of different complexity levels are proposed by applying Single Sideband (SSB) modulation and/or spectral gapping in AMOOFDM-SCM. It is shown that these AMOOFDM-SCM designs can support >60Gb/s signal transmission over at least 20km, which is >1.5 times higher than that supported by the AMOOFDM modems. In the above-mentioned three AMOOFDM-SCM modems, two Inverse Fast Fourier Transform (IFFT)/ Fast Fourier Transform (FFT) operations are required in the transmitter/receiver. To reduce the transceiver complexity and system cost, three simplified AMOOFDM-SCM modems are proposed, each of which requires a single IFFT/FFT operation. These designs not only significantly simplify the AMOOFDM-SCM modem configurations but also offer extra network features such as input/output reconfigurability without compromising the transmission performance. To relax the requirements on parameters of key transceiver components such as Digital-to- Analogue Converters (DACs) and Analogue-to-Digital Converters (ADCs), a reduction in Peak-to-Average Power Ratio (PAPR) associated with an OFDM signal is necessary. To achieve such an objective, AMOOFDM using Phase Modulation (PM) (AMOOFDM-PM) is proposed and explored in IMDD SMF systems. AMOOFDM-PM utilises an electrical OFDM signal to modulate the phase of a RF carrier prior to performing optical intensity modulation. Compared to AMOOFDM, AMOOFDM-PM can considerably reduce the PAPRs of OFDM signals and simultaneously lower the minimum requirements on quantization bits and sampling rates of DACs/ADCs. To effectively compensate the DML frequency chirp effects, detailed investigations of dynamic negative power penalty characteristics of OOFDM signal transmission are undertaken in DML-based IMDD systems incorporating MetroCor fibres with negative dispersion parameters. Excellent agreement between numerical simulations and real-time experimental measurements is obtained over a wide diversity of system conditions. The physical mechanism underpinning the occurrence of negative power penalties is the reduction in subcarrier intermixing impairments due to the compensation between DML positive frequency chirp and MetroCor negative chromatic dispersion. It is also shown that the negative power penalty is independent of both cyclic prefix and signal modulation format, and, more importantly, controllable when adaptive modulation and/or appropriate adjustments of DML operating conditions are applied. Finally, for reducing the DML frequency chirp, a simple and effective chirp compensation technique is also proposed, which utilizes an electrical analogue circuit and an optical phase modulator. The electrical analogue circuit produces a phase signal mimicking the original phase of the DML-modulated optical signal, and the optical phase modulator driven by the generatedp hases ignal compensatesth e DML frequency chirp. In DMLIIbased IMDD AMOOFDM PON systems, the technique can almost completely alleviate the DML frequency chirp effect and simultaneously improve the transmission capacity by approximately 25% for transmission distances in a range of 30-80km. In addition, the technique is also robust to variations in DML operating conditions. The results presented in the thesis can provide valuable technical solutions for further improving the OOFDM transmission capacity, performance robustness and system flexibility, as well as simultaneously reducing the transceiver complexity and system cost for cost-sensitive NG-PONs.
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Tariq, Sana. "Inside all-optical networks /." Online version of thesis, 2009. http://hdl.handle.net/1850/10960.
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Rozas, David. "Generation and Propagation of Optical Vortices." Digital WPI, 1999. https://digitalcommons.wpi.edu/etd-dissertations/348.
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"Optical vortices are singularities in phase fronts of laser beams. They are characterized by a dark core whose size may dramatically affect their behavior upon propagation. Previously, only large-core vortices have been extensively studied. The object of the research presented in this dissertation was to explore ways of generating small-core optical vortices (also called optical vortex filaments), and to examine their propagation using analytical, numerical and experimental methods. Computer-generated holography enabled us to create arbitrary distributions of optical vortex filaments for experimental exploration. We used hydrodynamic paradigms to develop an heuristic model which described the dependence of vortex motion on other vortices and the background beam, both qualitatively and quantitatively. We predicted that pair of optical vortex filaments will rotate with angular rates inversely proportional to their separation distance (just like vortices in a fluid). We also reported the first experimental observation of this novel fluid-like effect. It was found, however, that upon propagation in linear media, the fluid-like rotation was not sustained owing to the overlap of diffracting vortex cores. Further numerical studies and experiments showed that rotation angle may be enhanced in nonlinear self-defocusing media.
The results presented in this thesis offer us a better understanding of dynamics of propagating vortices which may result in applications in optical switching, manipulation of micro-particles and optical limiting."
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Tomljenovic-Hanic, Snjezana. "Propagation effects in optical waveguides, fibres and devices /." View thesis entry in Australian Digital Theses Program, 2003. http://thesis.anu.edu.au/public/adt-ANU20040921.104741/index.html.
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Liang, Yu, and 梁羽. "Versatile photonic processor based on fiber optical parametric amplifiers." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43085362.
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Liang, Yu. "Versatile photonic processor based on fiber optical parametric amplifiers." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43085362.
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Agapiou, George S. "Mode index transitions in planar optical waveguides." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/15404.
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