Dissertations / Theses: 'Laser communication systems'

1

Sabala, Ryan J. "Satellite Attitude Determination Using Laser Communication Systems." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1218636153.

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2

Sofka, Jozef. "New generation of gimbals systems for aerospace applications." Diss., Online access via UMI:, 2007.

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3

Qureshi, Zihad. "Vertical cavity surface emitting lasers in high speed optical data communications." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608126.

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4

Bar, Siman Tov Omar. "Adaptive optimization of a free-space laser communication system under dynamic link attenuation." Diss., Online access via UMI:, 2009.

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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Electrical and Computer Engineering, 2009.
Includes bibliographical references.

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5

Bonk, Scott S. "The use of point-to-point lasers for navy ships." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FBonk.pdf.

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6

Timus, Oguzhan. "Free space optic communication for Navy surface ship platforms." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FTimus.pdf.

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7

Zhu, Benyuan. "Multichannel grating cavity laser for optically multiplexed communication systems." Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320438.

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8

Lee, Myron S. M. Massachusetts Institute of Technology. "Optomechanical and wavelength alignments of CubeSat laser communication Systems." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112470.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 97-100).
While the introduction of CubeSats has enabled the scientific, commercial, and governmental communities to launch space missions more quickly at lower costs, the communication subsystems of the platform are limited by a heavily regulated and overcrowded RF spectrum. Scientific instruments with increasing capabilities on CubeSats are generating massive amounts of data and are quickly pushing the boundaries of the data rates of current RF communication systems. An alternative to the traditional RF communication system is the free space optical (FSO) communication system. With higher power efficiency, FSO communication, or lasercom, can potentially provide higher data rates using less power and also avoid the RF spectrum regulatory process. MIT's Nanosatellite Optical Downlink Experiment (NODE) is an effort to demonstrate low cost and high speed optical downlink from LEO for CubeSats, and this thesis focuses on alignments in the optomechanical system and transmitter system of the NODE payload. First, simulation and analyses are performed on an optomechanical model of NODE to study the effects potential misalignments of hardware components can have on the overall system. Second, we present an autonomous optimization algorithm that monitors the conditions of the transmitter system and compensates for wavelength misalignments between the transmitter optical components caused by variations in the thermal environment.
by Myron Lee.
S.M.

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9

Johnson, Peter Thomas. "Spectral correlation of semiconductor laser." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385428.

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10

Hill, Timothy J. "Interference of intensity noise in a multimode Nd:YAG laser." Title page, abstract and contents only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phh6484.pdf.

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Includes bibliographical references (leaves 151-163). Investigates the behaviour of the intensity noise in a multimode Nd:YAG laser. The collective modes of oscillation are excited by broadband ambient noise. Because the phase of the excitation is unknown, a cross spectral technique to measure the antiphase dynamics directly and form a picture of the intensity noise interference for two to five mode operation is developed. For three mode operation, the contributions of the longitudinal modes to collective modes is measured.

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11

Liu, Zhao. "Modeling and measurement of the effects of atmospheric turbulence and platform vibrations on laser communication." Diss., Online access via UMI:, 2009.

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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Electrical and Computer Engineering, 2009.
Includes bibliographical references.

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12

Leung, Ian Kin-Hay Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. "Development of composite cavity fibre lasers for fibre laser hydrophone systems." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/41248.

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In this thesis, my main focus was to establish a novel composite-cavity fibre laser (CCFL) and to apply it in sensing, particularly in the hydrophone application. The CCFL that I have proposed is formed by writing three wavelength matched fibre Bragg gratings directly into a continuous length of doped fibre. I have also examined the relative advantages and disadvantages of interferometric and intensity-based hydrophone systems, and have established a hydrophone system that can be switched between the two modes of operation, by making use of digital signal processing. I have established a theoretical model to study the lasing and spectral characteristics of the CCFL. My analysis showed that whilst the CCFL have significantly different phase and threshold conditions from the common semiconductor diode lasers with external cavity, the CCFL also have mode-limiting properties that are often sought after. Through simulations, I was able to identify that a non-uniform straining scheme, that is, when one of the sub-cavities of the CCFL is restrained from strain, can improve the sensitivity with respect to existing single cavity fibre lasers, in both the frequency and intensity domains. My simulations also showed that the sensitivity of such a straining scheme can be optimised by tuning the reflectivity of the gratings, sub-cavity lengths, doping concentration and pump power. I have fabricated multiple CCFLs using the in-house grating writing facilities, and have experimentally assessed their power and spectral related lasing characteristics. Whilst having a significantly longer total cavity length compared to typical fibre lasers, the CCFLs demonstrated stable single longitudinal mode operation and narrow linewidth in the order for a few tens of kHz. Asymmetric output power and frequency as a result of unequal sub-cavity lengths were also examined. Finally, I conducted sensing experiments by applying the CCFLs in strain monitoring and intensity-based hydrophone. My results showed that the non-uniform straining scheme had significantly improved the intensity response of the CCFL, and that the acoustic pressure and frequency can be determined by directly sampling and applying Fourier transform to the output intensity of the fibre laser.

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13

Neo, Soo Sim Daniel. "Free space optics communication for mobile military platforms." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FNeo.pdf.

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14

Modi, Sohrab. "Free space laser communications on the Macintosh computers /." Online version of thesis, 1990. http://hdl.handle.net/1850/10547.

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15

Ketprom, Urachada. "Line-of-sight propagation of optical wave through multiple-scatter channel in optical wireless communication system /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6057.

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16

Merritt, Elizabeth C. "The effects of extremely-short external cavity optical feedback into a modulated vertical-cavity surface-emitting laser /." Connect to online version, 2007. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2007/234.pdf.

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17

Lomax, Andrew Martin. "Picosecond pulse control using semiconductor laser amplifiers." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333329.

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18

Ikpe, Stanley A. Triplett Gregory Edward. "Atmospheric effects on near-infrared free space optical communication links." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6654.

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Title from PDF of title page (University of Missouri--Columbia, viewed on March 10, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. Gregory E. Triplett Jr. Includes bibliographical references.

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19

Khandekar, Rahul M. "Advanced wavefront manipulation technologies in optical systems." Diss., Online access via UMI:, 2008.

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Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Electrical Engineering, 2008.
Includes bibliographical references.

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20

Davies, A. R. "Novel applications of monolithic tunable laser diodes for optical communication systems." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598359.

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In order to facilitate the increasing traffic demands of optical communications networks high-speed transmitters will be required in future systems. This thesis focuses on routes to achieving 40Gb/s data rates using advanced modulation formats and direct modulation of Distributed Feedback (DFB) semiconductor laser diodes. In particular four-level signalling is employed as a way of achieving 40Gb/s data rates from existing state-of-the-art DFB lasers which are typically limited to speeds of around 20GHz. The potential of using four-level signalling to extend the reach of future systems is demonstrated for the first time by 40Gb/s uncooled signal generation. Transmission tests confirm the feasibility of the technique used and spectral efficiency measurements further show the benefit that can be gained by using advanced modulation formats. The use of four-level signalling is extended by demonstration of a novel technique which alleviates some of the complicated electronics usually required by multi-level signalling systems. A twin-contact DFB laser is employed to demonstrate the principle of four-level signal generation by differential amplitude modulation. Results are presented which show the feasibility of the technique and observations are made on the limitations of the device used in experimental demonstration. This leads to the use of a time-resolved travelling wave laser model. The model is adapted to support simulation of multi-section devices with spatially varying injection currents. Extensive simulation is used to suggest an optimised device structure for the generation of four-level signals. A three-contact device geometry is suggested and further work is presented on fabricating such a structure. Focussed-ion- beam-etching of a ridge- waveguide index coupled DFB is carried out to fabricate the optimised device structure and results are presented which confirm the benefits that can be gained by using a multi-contact device for multi-level signal generation.

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21

Falkenburg, Grant (Grant E. ). "High-order compensation of self-phase modulation in laser communication systems." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112845.

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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (page 72).
Self-phase modulation (SPM) creates a power and fiber-length dependent spectral broadening that reduces signal-to-noise ratio in free-space laser communication systems which use a fiber to connect their transmitter's high-power optical amplifier to its telescope optics. The effects of SPM can be mitigated by using a phase modulator to down-chirp pulses before passing through the receiver's matched filter. This thesis tests and evaluates a new SPM compensation technique-applying a phase modulation determined from a measurement of the SPM-distorted waveform's optical intensity-and benchmarks it against sinusoidal phase modulation compensation. The spectra and throughput of the compensated signal are calculated and measured to determine the effectiveness of the new technique. It is found that the two techniques perform within 0.2 dB of each other for fiber lengths less than three times the nonlinear length, and it is expected that the new technique will outperform sinusoidal phase modulation for greater fiber lengths.
"This material is based upon work supported under Air Force Contract No. FA8721-05-C-0002 and/or FA8702-15-D-0001"--Title page.
by Grant Falkenburg.
M. Eng.

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22

West, Lamar. "Analysis and simulation of reverse path laser clipping in subcarrier multiplexed hybrid fiber coax networks." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/13301.

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23

Manuel, de Castro Faria Salgado Henrique. "Performance assessment of subcarrier multiplexed optical systems : implications of laser nonlinearities." Thesis, Bangor University, 1993. https://research.bangor.ac.uk/portal/en/theses/performance-assessment-of-subcarrier-multiplexed-optical-systems(dde01341-f26c-4fa6-b546-8baad0c38ec2).html.

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This thesis is concerned with a detailed study of laser nonlineanties and the implications for multichannel subcamer multiplexed fibre optic systems. In view of the limitations of previously reported analytic treatments of laser nonlinear distortion, a considerable part of the study is dedicated to the development of modelling and analytic tchniques suitable for practical system design and optimisation The single-mode rate equations provide an adequate basis for the analysis of laser intnnsic dynamic distortion and relative intensity noise and their dependence on device parameters and operating conditions. The Volterra series method of nonlinear system theory is then applied and an analytical model is obtained that describes the nonlineanty in the frequency domain by a set of nonlinear transfer functions This method provides a ngorous analytic nonlinear model that takes into account all the intermodulation products up to third-order as determined by the rate equations Moreover, the laser response to the important case of a sum of narrow-band signals is considered and under certain conditions, which are valid for the majority of systems of interest, the intermodulation power spectral density of the distortion products is determined This enables an accurate evaluation of the impact on the overall system performance of laser intrinsic distortion and optimum overall performance is identified after including the noise introduced in the detection process The relative importance of laser intnnsic distortion and clipping-istortion is also examined. Finally, the analytic model is used to investigate design constraints and the overall system performance of relevant SCM systems. Case studies are considered that demonstrate the applicability of the method devised.

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Chung, Chul-Jong. "Practical performance and system capacity of lightwave AM SCM video systems." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/39975.

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25

Da, Silva H. J. A. "Influence of laser frequency chirp on the performance of optical communication systems." Thesis, Bangor University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383573.

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26

Walton, Channing. "Pattern controlled single mode optical data streams from gain switched semiconductor laser diodes." Thesis, University of Kent, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332603.

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27

Butaney, Vikas Hari. "Measurements, analysis and modeling of the performance of direct detection receivers with an optical preamplifier." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-11102009-020152/.

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28

Corbett, Kerry. "Modelling and experiments on the behaviour of injection current modulated multimode semiconductor lasers." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phc7891.pdf.

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Bibliography: p. 215-231. This thesis investigates the behaviour of semiconductor lasers under large amplitude sinusoidal current modulations. It focuses directly on the behaviour of Faby-Perot lasers under direct modulation of the injection current.

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29

Sánchez, Costa Christian. "Optical Orthogonal Frequency Division Multiplexed communication systems: analysis, design and optimization." Doctoral thesis, Universitat Politècnica de València, 2014. http://hdl.handle.net/10251/39375.

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En este trabajo se realiza una intensiva labor teórica de descripción de sistemas de comunicaciones ópticas que utilizan la técnica de multiplexación por división de frecuencias ortogonales (OFDM en inglés), más concretamente en sistemas con modulación directa de la intensidad de un láser y detección directa. Se parte pues de un modelo analítico que estudia con detalle todos aquellos fenómenos que afectan a la señal de información detectada en el receptor. Tales fenómenos son: la nolinealidad del láser, las modulaciones de intensidad y de fase ópticas, la propagación a través de la fibra óptica teniendo en cuenta la dispersión cromática de primer orden, y la detección de intensidad óptica final mediante un detector de ley cuadrática. El modelo analítico es validado mediante comparaciones con resultados obtenidos a través de simulaciones con software comercial. Dada la característica singularidad de las señales OFDM debidas a su naturaleza multi-portadora, la amplitud de la señal generada es aleatoria, y el modelo analítico es complementado con un estudio que contempla el recorte o "clipping" en el transmisor. Además, se tiene en cuenta los efectos de filtrado de la señal a lo largo de sistema de comunicaciones. Con el trabajo analítico realizado se está en disposición de realizar una descripción bastante completa de los principales fenómenos y realizar estudios para evaluar el funcionamiento final ante diferentes valores de los parámetros del sistema. Es bien sabido que los sistemas de comunicaciones ópticas con modulación y detección directa se ven perjudicados por la distorsión no lineal, que para señales multi-portadora como OFDM se traduce en la mezcla de los símbolos de información que transportan las diferentes subportadoras. Para mitigar la distorsión no lineal y así mejorar el funcionamiento del sistema, se propone el uso de una técnica de pre-distorsión que se basa en el modelo analítico previamente propuesto. Esta técnica mejora la eficiencia de modulación, haciendo posible incrementar el término de la señal de información sin que se vea incrementada la distorsión no lineal en el receptor. La técnica aquí propuesta se compara también con otra ya publicada con el objetivo de evaluar su funcionamiento. Otra técnica para la mejora de sistemas con modulación y detección directas es la realizada mediante filtrado óptico. Aunque se conoce de forma más o menos intuitiva su funcionamiento para formatos de modulación ópticos tradicionales, es preciso disponer de una formulación matemática para señales ópticas OFDM para entender de forma exacta su principio de operación, las mejoras obtenidas, así como su potencial. En esta estapa se realiza esta formulación matemática ampliando el análisis teórico previamente propuesto, y se aplica para evaluar el funcionamiento obtenido con diversas estructuras de filtrado óptico. Finalmente, puesto que un potencial escenario de funcionamiento para señales ópticas OFDM son las redes de acceso donde operan más de un usuario, se propone y se estudia la técnica "interleaving division multiple access" (IDMA) en combinación con OFDM.
Sánchez Costa, C. (2014). Optical Orthogonal Frequency Division Multiplexed communication systems: analysis, design and optimization [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/39375
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Ramirez-Hernandez, Ramiro A. "Additively Manufactured On-Package Multipolar Antenna Systems for Harsh Communication Channels." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7705.

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Four main aspects are studied and explored throughout this dissertation: (1) On-Package Multipolar antenna system design for integration with commercial wireless sensor nodes for machine-to-machine communication applications; (2) Development of a novel MMIC packaging process and subsequent antenna integration for chip-to-chip communication applications, (3) Design and characterization of additively manufactured lumped passive elements for integration with MMIC and hybrid circuits, (4) Design and characterization of antennas for on- and off-metal radio frequency identification (RFID) applications. This work presents the design of different 3-D printed tripolar antenna systems operating at 2.4 GHz. The antennas are designed for integration with commercial wireless nodes with the purpose of mitigating multipath and depolarization channel effects that might be present in many machine-to-machine (M2M) deployments. The antennas are fabricated utilizing an additive manufacturing (AM) approach that combines fused deposition modeling (FDM) of ABS plastic for dielectric parts and micro-dispensing of silver paste Du-Pont CB028 for conductive layers as the majority of the devices presented in this work. Over the air testing demonstrates a 1% channel improvement of up to 14 dB, achieved in a highly-reflective, Rayleigh-like fading environment by implementing selection diversity between three mutually orthogonal monopoles. This improvement leads to better bit error rate (BER) performance (as is also shown). Additionally, RSSI measurements show significant improvement when the prototype antenna system is integrated with commercial wireless sensor hardware. Implications of tripolar antenna integration on M2M systems include reduction in energy use, longer communication link distances, and/or greater link reliability. In order to incorporate the proposed multipolar selection diversity technique into short range wireless chip-to-chip communications, a novel and versatile 3D printed on-chip integration approach using laser machining is subsequently demonstrated for microwave and mm-wave systems in a process herein referred to as Laser Enhanced or Laser Assisted Direct Print Additive Manufacturing (LE-DPAM). The integration process extends interconnects laterally from a MMIC to a chip carrier. Picosecond laser machining is applied and characterized to enhance the 3D printing quality. Specifically, the width of micro-dispensed printed traces is accurately controlled within micrometer range (e.g. laser cuts ~12 μm wide), additionally, 150 μm probe pads are cut in order to facilitate RF measurement. The S-parameters of a distributed amplifier integrated into the package are simulated and measured from 2 to 30 GHz. It is seen how the overall performance is significantly better than a traditional wirebonded QFN package and previously reported AM MMIC interconnections. The attenuation of the microstrip line including interconnects is only 0.2 dB/mm at 20 GHz and return loss with the package is less than 10 dB throughout the operating frequency band A 17 GHz package integrated linearly polarized patch antenna, fabricated with a multi-layer and multi-material LE-DPAM process is then introduced for vertical interconnection with a MMIC die. Performance is successfully measured and characterized achieving a return loss greater than 19 dB at the desired design frequency. Good agreement between simulated and measured radiation patterns is also obtained with a peak gain of 4.2 dBi. Another section of this work utilizes LE-DPAM to fabricate lumped capacitors and inductors for coplanar waveguide (CPW) circuits, especially useful for filtering and matching network implementation. Laser machining is used to achieve ~12 µm slots on printed conductors, producing aspect ratios greater than 2:1, as well as to fabricate vertical interconnects or vias that allow for the fabrication of the multilayer inductors. Inductances in the range of 0.4-3 nH are achieved, with a maximum quality factor of 21, self-resonance frequencies up to 88 GHz, and an inductance per unit of area of 5.3 nH/mm2. Interdigital capacitors in the range of 0.05-0.5 pF are fabricated, having a maximum quality factor of 750 and self-resonances up to 120 GHz. All the components are made on the center line of a CPW that is 836 µm wide. The results show that LE-DPAM enables the fabrication of compact passive circuits that can be easily interconnected with MMIC dies, which at the same time, can be manufactured as part of a larger component. This enables the fabrication of structural electronics that are functional into the mm-wave frequency range. A final aspect of this work goes through antenna designs for specific RFID (radio frequency identification) applications. RFID tag design is generally focused specifically on either off-metal or on-metal configurations. In this work passive 2D and 3D RFID tags are presented which perform similarly in both configurations. The presented tags operate in the ISM RFID UHF bands that cover 864-868 MHz and 902-928 MHz. A matching loop consisting of two parallel stubs to ground is used for impedance matching to a passive integrated circuit, which has -18 dBm sensitivity. A planar 2D tag with a footprint of 13126.5 mm2 is first introduced, showing a simulated gain of approximately 3 dBi and a measured read range of 10 m (for 31 dBm transmit power from the reader) in both on-metal and off-metal conditions. The tag is miniaturized into a 3D geometry with a footprint of 2524.25 mm2 (520% reduction) and achieves the same broadside simulated on-metal gain. The antennas are fabricated using a DPAM process, and a meshed ground configuration is explored in order to accomplish a 50% conductive paste reduction without disrupting the performance. The proposed tags are compared with commercially available tags as well as previously published tags in terms of read range and size. The tags in this work present an improvement in terms of read range, gain, and area with respect to previous designs covering the ISM RFID UHF bands. Moreover, the performance of these tags is maintained in on- and off-metal conditions, achieving comparable performance and a reduction in volume of 11482% with respect to the best tag reported.

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31

Gross, Michael Charles. "High-rate, short-pulse sources:jitter and pedestal level in optical time-division multiplexing." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5405.

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Gross, Michael Charles. "High-rate, short-pulse sources jitter and pedestal level in optical time-division multiplexing /." Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180157/unrestricted/gross%5Fmichael%5Fc%5F200312%5Fphd.pdf.

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33

Rumbaugh, Scott Hamilton. "Endless state-of-polarization control for coherent optical communication systems using nematic liquid crystals." PDXScholar, 1989. https://pdxscholar.library.pdx.edu/open_access_etds/4145.

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One of the obstacles to coherent fiber-optic communications is the unpredictable polarization drift which necessitates the use of an active polarization controlling system to match the polarizations of the signal and local oscillator. The polarization match must be maintained during the reset of any of the finite range components to prevent loss of data. We present a novel and practical system which uses three liquid crystal devices for the polarization matching process. Also, the required reset control algorithm and its derivation are described in detail.

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Muramoto, Willian Sadaiti. "Estudo e modelagem de canal optico atmosferico utilizando o Lightsim como plataforma de simulação." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258925.

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Orientador: Edson Moschim
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-10T09:27:29Z (GMT). No. of bitstreams: 1 Muramoto_WillianSadaiti_M.pdf: 2409655 bytes, checksum: 095d332f24becfd479ff86a233ffcc95 (MD5) Previous issue date: 2007
Resumo: Este trabalho apresenta um estudo e simulações de um enlace atmosférico para comunicações ópticas e como os diversos fatores intrínsecos ao enlace podem influenciar na qualidade do sinal. O uso de um canal atmosférico para a propagação de um sinal óptico é chamado de FSO, Óptica do Espaço Livre, que é uma alternativa barata para enlaces de curto alcance, devido aos baixos custos no seu desenvolvimento, instalação e manutenção. A principal contribuição deste trabalho esta na reunião dos modelos matemáticos que caracterizam o enlace óptico atmosférico
Abstract: This is a study and simulation on free space optical communication analyzing many factors that can influence the transmitted signal quality. The use of an atmospheric channel to propagate optical signal is called FSO, Free Space Optics, and it is a cheap alternative for low length paths, because the low cost in it development, installation and maintenance. The mainly contribution for this work are in group many characteristic equations for atmospheric optical links
Mestrado
Engenharia de Computação
Mestre em Engenharia Elétrica

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35

Perera, Janaka P. "A low-cost man-portable free-space optics communication device for Ethernet applications." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FPerera.pdf.

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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2004.
Thesis advisor(s): Gamani Karunasiri, Xiaoping Yun. Includes bibliographical references (p. 47-50). Also available online.

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Fulenwider, Thomas Edward. "Modular Laser Combat System for Remotely Operated Vehicles: Bridging the Gap Between Computer Simulation and Live Fire." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/335.

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In the emerging industry of small unmanned vehicles, pioneered by small businesses and research institutions, a suitable combat system test platform is needed. Computer simulations are useful, but do not provide the definitive proof of effective operation necessary for deployment of a combat system. What is needed is an affordable simulated weapons system that enables live flight testing without the used of live weaponry. A framework is developed here for the construction of a simulated weapon using Free Space Optical (FSO) infrared communication. It is developed in such a way to ensure compatibility with a variety of platforms including ground and aerial vehicles, so that identical but configurable modules can be used on any vehicle that is to take place in a live combat simulation. A proof-of-concept implementation of this modular laser combat system framework is also presented and tested. The implemented system shows the value of such a simulated weapons system and future areas of improvement are also explored.

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Yin, Hujun. "Cross layer design and optimization of wireless networks /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/5904.

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Ajemian, Stephen P. "Modeling and evaluation of aerial layer communications system architectures." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90705.

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Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 90-91).
Airborne networks are being developed to provide communications services in order to augment space-based and terrestrial communications systems. These airborne networks must provide point to point wireless communications capabilities between aircraft and to ground-based users. Architecting airborne networks requires evaluating the capabilities offered by candidate aircraft to operate at the required altitudes to bridge communications among ground users dispersed over large geographic areas. Decision makers are often faced with choices regarding the type and number of aircraft to utilize in an airborne network to meet information exchange requirements. In addition, the type of radio required to meet user needs may also factor into the architecture evaluation for an airborne network. Aircraft and radio design choices must be made under cost constraints in order to deliver capable communications architectures at an acceptable cost. Evaluating communications architectures is often conducted with modeling and simulation. However, evaluations typically focus on specific network configurations and can become intractable when varying design variables such as aircraft and radio types due to the complexity of the trade space being analyzed. Furthermore, the growth in choices for design variables (such as additional aircraft types) can lead to enormous growth in the number of feasible candidate architectures to analyze. The methodology developed and presented herein describes an approach for evaluating a large number of architecture combinations which vary on aircraft type and radio type for representative airborne networks. The methodology utilizes modeling and simulation to generate wireless communications performance data for candidate aircraft and radio types and enumerates a large trade space through a computational tool. The trade space is then evaluated against a multi-objective decision model to rapidly down-select to a handful of candidate architectures for more detailed analysis. The results of this analysis provide effective tools for reducing the complex trade space to a tractable number of architectures to make an informed architectural decision with no prior articulation of preferences for performance measures. For the notional concept of operation analyzed, the number of feasible architectures was approximately 500,000 for each of the two radio types examined. The decision model implemented reduced the feasible architectures to approximately 50 near-optimal architectures for each radio type. From this manageable set of near-optimal architectures, an analysis is conducted to evaluate marginal benefits versus cost to further reduce the candidate architectures to 3 architectures for each radio type. From these remaining architectures, detailed analysis and visualization can be conducted to aid decision makers in articulating preferences and identifying a single "best" architecture based on mission needs. The enumeration of the trade space using the computational tool and multi-objective decision model is highly flexible to incorporating new constraints and generating new candidate architectures as stakeholder preferences become clearer. The trade space enumeration and decision model can be conducted rapidly to down-select large trade spaces to a tractable number of communications architectures to inform an architectural recommendation.
by Stephen P. Ajemian.
S.M. in Engineering and Management

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39

VanWiggeren, Gregory D. "Chaotic communication with erbium-doped fiber ring lasers." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/30299.

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40

Mostafa, Ayman. "Physical-layer security for visible-light communication systems." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61328.

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Visible-light communication (VLC) is an enabling technology that exploits the lighting infrastructure to provide ubiquitous indoor broadband coverage via high-speed short-range wireless communication links. On the other hand, physical-layer security has the potential to supplement conventional encryption methods with an additional secrecy measure that is provably unbreakable regardless of the computational power of the eavesdropper. The lack of wave-guiding transmission media in VLC channels makes the communication link inherently susceptible to eavesdropping by unauthorized users existing in areas illuminated by the data transmitters. In this thesis, we study transmission techniques that enhance the secrecy of VLC links within the framework of physical-layer security. Due to linearity limitations of typical light-emitting diodes (LEDs), the VLC channel is more accurately modelled with amplitude constraints on the channel input, rather than the conventional average power constraint. Such amplitude constraints render the prevalent Gaussian input distribution infeasible for VLC channels, making it difficult to obtain closed-form secrecy capacity expressions. Thus, we begin with deriving lower bounds on the secrecy capacity of the Gaussian wiretap channel subject to amplitude constraints. We then consider the design of optimal beamformers for secrecy rate maximization in the multiple-input single-output (MISO) wiretap channel under amplitude constraints. We show that the design problem is nonconvex and difficult to solve, however it can be recast as a solvable quasiconvex line search problem. We also consider the design of robust beamformers for worst-case secrecy rate maximization when channel uncertainty is taken into account. Finally, we study the design of linear precoders for the two-user MISO broadcast channel with confidential messages. We consider not only amplitude constraints, but also total and per-antenna average power constraints. We formulate the design problem as a nonconvex weighted secrecy sum rate maximization problem, and provide an efficient search algorithm to obtain a solution for such a nonconvex problem. We extend our approach to handle uncertainty in channel information. The design techniques developed throughout the thesis provide valuable tools for tackling real-world problems in which channel uncertainty is almost always inevitable and amplitude constraints are often necessary to accurately model hardware limitations.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

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41

Bennecer, Abdeldjalil. "Low cost integrated lasers for data communications." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609254.

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42

O, Cochlain Ciaran R. "Tunable erbium doped fibre lasers for lightwave communication systems." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283935.

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43

Seong, Kibeom. "Cross-layer resource allocation for multi-user communication systems /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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44

Rysdale, L. J. "Aspects of polarisation in coherent optical communication systems." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374439.

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45

Clements, Emily Baker. "Probabilistic methods for systems engineering with application to nanosatellite laser communications." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119286.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 109-121).
Risk-tolerant platforms such as nanosatellites may be able to accept moderate performance uncertainty if it enables the reduction of cost or improves manufacturability, in contrast to large-budget space missions. New uncertainty-based systems engineering approaches such as uncertainty-based multidisciplinary optimization require the use of integrated performance models with input distributions, which do not yet exist for complex systems, e.g. laser communications (lasercom) payloads. In this thesis, we present our development of a statistical, risk-tolerant systems engineering approach and apply it to nanosatellite-based design and architecture problems to investigate whether adding a statistical element to systems engineering enables improvements in performance, manufacturability, and cost. The scope of this work is restricted to a subset of nanosatellite-based lasercom systems, which are particularly useful given current momentum to field Earth observing nanosatellite constellations and challenges for data retrieval. We build uncertainty-based lasercom performance models for a low Earth orbiting (LEO) system being developed at MIT called the Nanosatellite Optical Downlink Experiment (NODE) as a reference architecture. Compared with a more traditional, deterministic systems engineering approach, we find our probabilistic approach leads to a lasercom downlink design with a 59% reduction in ground station diameter and a 46% reduction in space terminal power for equivalent probabilities of a LEO-ground system delivering 500 Gb/day. We compare the data volume and latency performance of five communication architectures for nanosatellite constellations with and without lasercom crosslinks: two ground stations vs. nine ground stations with (i and ii) lasercom and (iii and iv) X-band, and (v) UHF with one ground station. For example, we find that a 30-satellite Walker delta constellation of 6U satellites with an optical downlink to nine ground stations and optical crosslinks can achieve a similar data volume and latency to the large X-band network with no crosslinks, with a higher than 90% chance of achieving 7.5 Tb/day and less than 2 hour latency for high-priority data, at two-thirds the cost. While we focus on a nanosatellite lasercom application, the process for characterizing the input distributions and modeling performance is generalizable to other lasercom systems or space systems.
by Emily B. Clements.
Ph. D.

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46

Lightfoot, Leonard E. "An energy efficient link-layer security protocol for wireless sensor networks." Diss., Connect to online resource - MSU authorized users, 2006.

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Thesis (M.S.)--Michigan State University. Dept. of Electrical & Computer Engineering, 2006.
Title from PDF t.p. (viewed on Nov. 20, 2008) Includes bibliographical references (p. 49-55). Also issued in print.

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47

Ronny, Ang Toon Yiam. "Link Performance Analysis of a Ship-to-Ship Laser Communication System." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/6761.

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The benefits of high data rates, high directionality, low sidelobes, small size, light weight, and low power of laser communications (lasercom) as compared to radio frequency (RF) communications make laser an attractive option for ship-to-ship communications. The realization of the option requires ship-to-ship lasercom system design and mission planning, which, in turn, necessitates a lasercom link budget analysis and a parametric analysis of lasercom system design and operational parameters. The link budget analysis determines whether the energy of a laser signal is adequately transmitted to a receiver. The parametric analysis determines the lasercom system design and operational parameters that meet ship-to-ship lasercom requirements. Maritime environmental conditions (atmospheric and water surface conditions) that affect lasercom link budget are investigated. The link budget takes into consideration transmitted and received power, gains, propagation losses, and implementation losses. The results of the link budget analysis and the parametric analysis can be used to analyze and trade the design and operational parameters contributing to a link budget that meets communications requirements and to gain understanding of the operational boundaries and limitations of lasercom.

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48

Young, John Scott. "Characterisation of Fabry-Perot semiconductor lasers." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285444.

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49

Al-Orainy, Abdullah Abdulaziz. "Mutual interference in multichannel optical fibre communication system." Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276206.

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50

Ahmed, Alaa Hussain. "Physical layer network coding based communication systems in frequency selective channels." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3871.

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The demand for wireless communications is growing every day which requiresmore speed and bandwidth. In two way relay networks (TWRN), physical layer network coding (PLNC) was proposed to double the bandwidth. A TWRN is a system where two end users exchange data through a middle node called the relay. The two signals are allowed to be physically added before being broadcasted back to the end users. This system can work smoothly in flat fading channels, but can not be applied straightforward in frequency selective channels. In a multipath multi-tap FIR channel, the inter-symbol interference (ISI) spreads through several symbols. In this case, the symbols at the relay are not just an addition of the sent symbols but also some of the previous symbols from both sides. This not only causes a traditional PLNC to fail but also a simple one equalizer system will not solve the problem. Three main methods have been proposed by other researchers. The OFDM based PLNC is the simplest in terms of implementation and complexity but suffers from the disadvantages of the OFDMlike cyclic prefix overhead and frequency offset. The main disadvantage, however is the relatively low BER performance because it is restricted to linear equalizers in the PLNC system. Another approach is pre-filtering or pre-equalization. This method also has some disadvantages like complexity, sensitivity to channel variation and the need of a feedback channel for both end nodes. Finally, the maximum likelihood sequence detector was also proposed but is restricted to BPSK modulation and exponentially rising complexity are major drawbacks. The philosophy in this work is to avoid these disadvantages by using a time domain based system. The DFE is the equalizer of choice here because it provides a non-trivial BER performance improvement with very little increase in complexity. In this thesis, the problem of frequency selective channels in PLNC systems can be solved by properly adjusting the design of the system including the DFE. The other option is to redesign the equalizer to meet that goal. An AF DFE system is proposed in this work that provides very low complexity especially at the relay with little sensitivity to channel changes. A multi-antenna DNF DFE system is also proposed here with an improved performance. Finally, a new equalizer is designed for very low complexity and cost DNF approach with little sacrifice of BER performance. Matlab was used for the simulations with Monte Carlo method to verify the findings of this work through finding the BER performance of each system. This thesis opens the door for future improvement on the PLNC system. More research needs to be done like testing the proposed systems in real practical implementation and also the effect of adding channel coding to these systems.

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Dissertations / Theses on the topic 'Laser communication systems'

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