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Orientador: Cláudio Kitano / Banca: Edvaldo Assunção / Banca: Gilder Nader / Resumo: Atuadores piezelétricos flextensionais consistem de uma estrutura metálica flexível acoplada a uma piezocerâmica. A estrutura flexível deve amplificar os pequenos deslocamentos e/ou forças da piezocerâmica, e gerar grandes deslocamentos e/ou forças em diferentes pontos específicos de sua estrutura. Esses dispositivos constituem um mecanismo a estado sólido, sem partes móveis (como pinos ou juntas), sendo que seus deslocamentos/forças estão associados à flexibilidade/rigidez mecânica da estrutura metálica conectada à piezocerâmica. Outra classe de atuadores, mais geral, são os manipuladores multi-atuados, que constituem de uma estrutura multi-flexível acoplada a duas ou mais piezocerâmicas. Novamente, a estrutura multi-flexível atua como um transformador mecânico, amplificando e mudando a direção dos deslocamentos das piezocerâmicas. Tais dispositivos podem apresentar dois ou mais graus de liberdade, como o nano-posicionador XY (com dois graus de liberdade), a micro-garra (quatro graus de liberdade) e outros. Os atuadores piezoelétricos flextensionais e os manipuladores multi-atuados podem ser utilizados em manipulação celular, na manufatura de CIs, em micro-cirurgias, e em muitas outras aplicações. Atualmente, ambos os tipos de atuadores são projetados pela moderna técnica de otimização tipológica, um método computacional que combina algoritmos de otimização com o método de elementos finitos. A interferometria laser constitui uma técnica adequada para caracterizar ambos os tipos de atuadores, permitindo-se a medição de deslocamentos na faixa de poucos nanômetros à vários micrometros. Neste trabalho, utiliza-se um interferômetro de Michelson de baixo custo para medir o fator de calibração e a amplificação de deslocamentos de atuadores piezoelétricos flextensionais, bem como, a relação entre o deslocamento direto e cruzado... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Piezoelectric flextensional actuators consist of a flexible metal frame attached to a piezoceramic. The flexible frames must amplify the small displacements and/or forces at different specific points of their structures. These are solid state type devices, without moving parts (such as pins or joints) and their displacements/forces are associated to the mechanical flexibility/stiffness of the metal structure connected to the piezoceramic. A more generic class of actuators, are the multi-actuated manipulators, which are compose of a multi-flexible structure attached to two or more piezoceramics. Similarly, the multi-flexible structure acts as a mechanical transformer amplifying and changing the direction of the piezoceramic displacements. Such devices may have two or more degrees of freedom, as the XY nano-positioner (with two degrees of freedom), the micro-jaw (four degrees of freedom) and others. Piezoelectric flextensional actuators and multi-actuated manipulators can be used in cell manipulation, manufacture of CIs, micro-surgery and many other applications. Currently, both types of actuators are designed by the modern topology optimization technique, a computational method that combines optimization algorithms with the finite element method. The laser interferometry is a suitable technique to characterize both types of actuators, enabling the measurement of displacements ranging from few nanometers to several micrometers. In this work, it was used a low cost Michelson interferometer to measure the calibration factor and the displacement amplification of flextensional piezoelectric actuators, as well as the relationship between the direct and the coupled displacements in multi-actuated manipulators. A new interferometric method, highly sensitive and suitable to operate under optical narrow band phase modulation is presented. In this method, the actuators are drive by a triangular... (Complete abstract click electronic access below) / Mestre

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This Thesis proposes phase modulating interferometry as an alternative to phase stepping and phase-shifting interferometry for use in the shape and displacement characterization of microelectromechanical systems (MEMS) [Creath, 1988; de Groot, 1995a; Furlong and Pryputniewicz, 2003]. A phase modulating interferometer is developed theoretically with the use of a stroboscopic illumination source and implemented on a Linnik configured interferometer using a software control package developed in the LabVIEWâ„¢ programming environment. Optimization of the amplitude and phase of the sinusoidal modulation source is accomplished through the investigation and minimization of errors created by additive noise effects on the recovered optical phase. A spatial resolution of 2.762 µm over a 2.97x2.37 mm field of view has been demonstrated with 4x magnification objectives within the developed interferometer. The measurement resolution lays within the design tolerance of a 500Ã… ±2.5% thick NIST traceable gold film and within 0.2 nm of data acquired under low modulation frequency phase stepping interferometry on the same physical system. The environmental stability of the phase modulating interferometer is contrasted to the phase stepping interferometer, exhibiting a mean wrapped phase drift of 40.1 mrad versus 91 mrad under similar modulation frequencies. Shape and displacement characterization of failed µHexFlex devices from MIT's Precision Compliant Systems Laboratory is presented under phase modulating and phase stepping interferometry. Shape characterization indicates a central stage displacement of up to 7.6 µm. With a linear displacement rate of 0.75 Ã…/mV under time variant load conditions as compared to a nominal rate of 1.0 Ã…/mV in an undamaged structure [Chen and Culpepper, 2006].

The wavelength-division multiplexing (WDM) is a well know technique capable of increasing the total capacity of a lightwave communication system; however, the system performance can be significantly limited by the dispersive and nonlinear effects, among others. This dissertation is mainly focused on the nonlinear effects upon the short-haul and long-haul lightwave systems.The short-haul lightwave system is mainly adopted in the access network. A passive optical access network is generally used to connect individual homes to a central office of a local area, and since there is no active component installed outside the central office of the passive optical access network, the system complexity and maintenance frequency can be significantly reduced. This dissertation provides a long-reach passive optical network (LR-PON) which can further reduce the system complexity and system cost. We found that four-wave mixing (FWM) and Rayleigh backscattering induced crosstalk were two main reasons to degrade the transmission performance in our proposed LR-PON. The long-haul lightwave system is mainly adopted in the transoceanic application. Although differential phase-shit keying (DPSK) modulation format has been confirmed to be suitable for long-haul WDM system, we found that a performance dip can be observed near the system zero dispersion avelength. In this dissertation, we designed various experiments to confirm the nonlinear effect to cause the performance dip being observed, and concluded that self-phase modulation (SPM) was the dominant reason to cause the performance dip rather than cross-phase modulation (XPM) or nonlinear phase noise.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / It is widely recognized that telemetry channels, particularly airborne channels, are afflicted by multipath propagation effects. It has also been shown that adaptive equalization can be highly effective in mitigating these effects. However, numerous other factors influence the behavior of adaptive equalization, and the type of modulation employed is certainly one of these factors. This is particularly true on modulations which exhibit different operating bandwidths. In this paper, we will examine the effect multipath and adaptive equalization for three modulation techniques which are either already in use, or have been proposed, for airborne telemetry.

All-optical signal processing. In current and future optical communication systems and networks, the data rate per wavelength has been approaching the speed limitation of electronics. Thus, all-optical signal processing techniques are highly desirable to support the necessary optical switching functionalities in future ultrahigh-speed optical packet-switching networks. To cope with the wide use of optical phase-modulated signals, in the thesis, an all-optical logic for DPSK or PSK input signals is developed, for the first time. Based on four-wave mixing in semiconductor optical amplifier, the structure of the logic gate is simple, compact, and capable of supporting ultrafast operation. In addition to the general logic processing, a simple label recognition scheme, as a specific signal processing function, is proposed for phase-modulated label signals. The proposed scheme can recognize any incoming label pattern according to the local pattern, and is potentially capable of handling variable-length label patterns. / In recent years, optical phase modulation has attracted much research attention in the field of fiber optic communications. Compared with the traditional optical intensity-modulated signal, one of the main merits of the optical phase-modulated signal is the better transmission performance. For optical phase modulation, in spite of the comprehensive study of its transmission performance, only a little research has been carried out in terms of its functions, applications and signal processing for future optical networks. / Optical access network with multicast overlay and centralized light sources. In the arena of optical access networks, wavelength division multiplexing passive optical network (WDM-PON) is a promising technology to deliver high-speed data traffic. However, most of proposed WDM-PONs only support conventional point-to-point service, and cannot meet the requirement of increasing demand on broadcast and multicast service. In this thesis, a simple network upgrade is proposed based on the traditional PON architecture to support both point-to-point and multicast service. In addition, the two service signals are modulated on the same lightwave carrier. The upstream signal is also remodulated on the same carrier at the optical network unit, which can significantly relax the requirement on wavelength management at the network unit. / Optical time-division multiplexing and demultiplexing. With the ever-increasing demand on communication bandwidth, optical time division multiplexing (OTDM) is an effective approach to upgrade the capacity of each wavelength channel in current optical systems. OTDM multiplexing can be simply realized, however, the demultiplexing requires relatively complicated signal processing and stringent timing control, and thus hinders its practicability. To tackle this problem, in this thesis a new OTDM scheme with hybrid DPSK and OOK signals is proposed. Experimental investigation shows this scheme can greatly enhance the demultiplexing timing misalignment and improve the demultiplexing performance, and thus make OTDM more practical and cost effective. / These issues are systematically investigated in this thesis. The research findings suggest that optical phase modulation and its signal processing can greatly facilitate flexible network functions and high bandwidth which can be enjoyed by end users. In the thesis, the most important physical-layer technology, signal processing and multiplexing, are investigated with optical phase-modulated signals. Novel and advantageous signal processing and multiplexing approaches are proposed and studied. Experimental investigations are also reported and discussed in the thesis. / Deng, Ning. / "August 2007." / Adviser: Calvin Chun-Kit Chan. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1196. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 119-127). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

Long distance repeaterless optical fiber communications systems are currently used to transmit most internet and telephone information worldwide. The growth of photonic telecommunications technology has produced systems with very high bit-rate per fiber, but this still falls short of its potential capacity. Currently systems that are able to transmit even higher bit-rates are being developed utilizing dense wavelength-division-multiplexing (WDM) to maximally utilize the bandwidth potential of optical fibers. One of the most important factors that limits the bit-rate achievable in a such a WDM optical communications system is the cross-talk between channels caused by pulse collisions. In this thesis a consistent mathematical theory is used to analyze the frequency and timing shifts caused collisions between two WDM channels. This theory is applied to the systems currently most promising for next-generation photonic telecommunications; the dispersion managed (DM) soliton and 'quasi-linear' systems. Self-contained formulae are obtained which accurately predict the timing shifts suffered in these systems with a wide range of parameters. These formulae require an order of magnitude less computational time that direct numerical simulations. Several mathematical techniques are introduced to obtain computationally efficient formulae for complete and incomplete collisions in both systems. For complete collisions we use the Poisson sum transform to change the calculation to a sum in the Fourier domain. For incomplete collisions we use asymptotic integration to obtain approximate formulae. For quasi-linear systems we simplify the Laplace method even further to obtain elementary formulae. We show that using a combination of these methods the timing shift for incomplete and complete collisions in a wide range of system configurations can be obtained in comparatively small computational times. We find that for systems with small DM map strength the timing shift from widely separated channels is significant. For quasi-linear systems with large DM map strength this is negligable and the timing shift decreases with the square of the channel frequency separation. We also find the timing shift from closely spaced channels is higher for quasi-linear systems than for DM soliton systems operating at the same average dispersion.

The decay of higher order solitons in optical fiber, initiated by localized channel perturbations such as a step change in dispersion, a localized loss element, or a bandpass filter, is explored theoretically and experimentally as a means of generating pairs of pulses having wavelengths that are up and down-shifted from the input wavelength. The achievable wavelength separation between the two sub pulses increases with increasing the amount of perturbations. Pulse parameter requirements for achieving useful wavelength shifts while avoiding unwanted nonlinear effects are presented. Experimental studies for N=2 solitons having 1 ps initial width are performed to demonstrate tunable wavelength conversion using a step change in dispersion and using a loss element. Wavelength shifts are tunable by varying the magnitude of a dispersion step or loss element that is used to disrupt the soliton cycle. Competing nonlinear effects, such as cubic dispersion, self-steepening, and stimulated Raman scattering, can be minimized by using input pulsewidths of one picosecond or greater. The separated pulses at two wavelengths can in principle be amplified to form separate higher order solitons. The process repeated to produce multiple wavelength replicas of an input data stream, and may thus be of possible use in multi-casting applications in fiber communication systems. The possibility of soliton recovery is also studied. For soliton recovery, conditions are stringent, in that the precise temporal overlap and phase relationship between sub-pulses that occurred at the point of separation is in principle needed at the reverse perturbation location. Experimental studies on soliton recovery for an N=2 soliton is performed by using a dispersion-compensated intermediate link, and reversing the dispersion step. Detrimental effects on soliton recovery are studied.

The continuous phase modulation (CPM) has a constant envelope and compact output power spectrum that makes it a promising underlying technology for power and spectrum efficient broadband wireless communications. However, high implementation complexity (especially the complexity of the receiver) required to deal with the phase memory and inter-symbol interference has impeded its adoption for broadband wireless communications, and only a few simple CPM modulation schemes have mainly been used, e.g. binary MSK and GMSK. Thus, research on efficient CPM transceivers to reduce the computational and hardware complexity is important. The major contribution of this dissertation is the development of novel frequency domain processing techniques and transceiver strategies to improve power and spectral efficiency, and reduce the complexity of CPM modulation schemes. First, this dissertation presents simplified frequency domain receiver structures and decoding schemes in the frequency domain for binary and M-ary CPM block transmission. The frequency domain receivers utilize parallel and serial structures with frequency domain processing which considerably reduces hardware and computational complexity compared to conventional time-domain processing. In addition, the decoding schemes in the frequency domain eliminate the controlled phase memory through frequency domain phase equalization instead of maximum-likelihood sequential decoders, e.g. Viterbi decoders. Second, frequency domain channel estimation schemes for CPM block transmission are presented, which adopt superimposed training signals to achieve bandwidth and power efficiency while reducing the complexity. In these schemes, the proposed frequency domain channel estimation uses the superimposed training signals as a reference signal to reduce the throughput loss caused by conventionally multiplexed training signals. Superimposed training signal design is presented, and the trade-off between bandwidth efficiency and power efficiency is also analyzed. Third, block transmission schemes and frequency domain equalization methods for CPM are proposed, which consider linear processing instead of conventional decomposition-based processing. The schemes of frequency domain linear processing avoid the complexity overhead (both in computation and hardware) of conventional orthogonal- or Laurent decomposed-based equalizers. Finally, this dissertation extends CPM block transmission and frequency domain equalization to phase-coded (time-varying modulation index) CPM, which shows better error performance and bandwidth efficiency than fixed modulation index CPM's. / text