<p>Fiber-optic communication systems have revolutionized the telecommunications industry and have played a major role in the advent of the Information Age. Thousands of kilometers of optical fiber are used by telecommunications companies to transmit telephone signals, Internet communication, and cable television signals throughout the world. So, working in this area has always been interesting. This thesis analyzes the nonlinearity of fiber-optic systems and proposes a system to mitigate fiber nonlinear e®ects. The topics of this thesis can be categorized into two parts. In the first part of thesis (Chapters 2, 3, and 4), analytical models are developed for fiber-optic nonlinear effects. It is important to have an accurate analytical model so that the impact of a specific system/signal parameter on the performance can be assessed quickly without doing time-consuming Monte-Carlo simulations. In the second part (Chapters 5, and 6), a multi-core/fiber architecture is proposed to reduce the nonlinear effects.</p> <p>In Chapter 2, intrachannel nonlinear impairments are studied and an analytical model for the calculation of power spectral density (PSD) and variance of the non- linear distortion is obtained based on quadrature phase-shift keying (QPSK) signal. For QPSK signals, intrachannel four-wave mixing (IFWM) is the only stochastic non- linear distortion. To develop the analytical model, a first order perturbation theory is used. For a Gaussian pulse shape, a closed form formula is obtained for the PSD of IFWM. For non-Gaussian pulses, it is not possible to find the PSD analytically. However, using stationary phase approximation approach, convolutions become multiplications and a simple analytical expression for the PSD of the nonlinear distortion can be found. The total PSD is obtained by adding the PSD of amplified spontaneous emission (ASE) PSD to that of the nonlinear distortion. Using the total PSD, bit error ratio (BER) can be obtained analytically for a QPSK system. The analytically estimated BER is found to be in good agreement with numerical simulations. Significant computational effort can be saved using the analytical model as compared to numerical simulations, without sacrificing much accuracy.</p> <p>In Chapter 3, the same approach as that in Chapter 2 is used to find an analytical expression for the PSD of the intrachannel nonlinear distortion of a fiber-optic system based on quadrature amplitude modulation (QAM) signal. Unlike the QPSK signal, intrachannel cross-phase modulation (IXPM) is a stochastic process for the QAM signal which leads to the increase of the nonlinear distortion variance. In this chapter, analytical expressions for the PSDs of self-phase modulation (SPM), IXPM, IFWM, and their correlations are obtained for the QAM signal. Simulation results show good agreement between the analytical model and numerical simulation.</p> <p>In Chapter 4, inter-channel nonlinear impairment is studied. This time, a first order perturbation technique is used to develop an analytical model for SPM and cross-phase modulation (XPM) distortions in a wavelength division multiplexing (WDM) system based on QAM. In this case, SPM distortion is deterministic and does not contribute to the nonlinear noise variance. On the other hand, XPM is stochastic and contributes to the noise variance. In this chapter, effects of input launch power, fiber dispersion, system reach, and channel spacing on the nonlinear noise variance are investigated as well.</p> <p>In Chapter 5, a single-channel multi-core/fiber architecture is proposed to reduce intrachannel fiber nonlinear effects. Based on the analytical model obtained in the first part of thesis, the nonlinear distortion variance scales as P³, where P is the fiber input launch power, which suggests that decreasing the fiber input power can reduce the nonlinear distortion significantly. In this system, the input power is divided between multiple cores/fibers by a power splitter at the input of each span and a power combiner adds the output fields of multiple cores/fibers so that one amplifier can be used for each span. In this case, each core/fiber receives less power and hence adds less nonlinear distortion to the signal. In a practical system, individual fiber parameters are not identical; so the optical pulses propagating in the fibers undergo different amounts of phase shifts and timing delays due to the fluctuations of fibers' propagation constants and fibers' inverse group speeds. Optical and electrical equalizers are proposed to compensate for these inter-core/fiber dispersions. In the case of an optical equalizer, adaptive time shifters and phase shifters are adjusted such that the maximum power is obtained at the output of power combiner. Our numerical simulation results show that for unrepeatered systems, the performance (Q factor) is improved by 6.2 dB using 8-core/fiber configuration as compared to single- core fiber system. In addition, for multi-span system, the transmission reach at BER of 2.1*10^-3 is quadrupled in 8-core/fiber configuration.</p> <p>In Chapter 6, a multi-channel multi-core/fiber architecture is proposed to reduce the inter-channel nonlinear distortions. In this architecture, different channels of a WDM system are interleaved between multiple cores/fibers which increases the channel spacing in each core/fiber. Higher channel spacing decreases the inter-channel nonlinear impairments in each core/fiber which leads to system performance improvement. At the end of each span, a multiplexer adds the channels from different cores/fibers so that one amplifier can be used for all of the channels. Unlike the single-channel multi-core/fiber system, the WDM multi-core/fiber system does not require equalizers since different cores/fibers carry channels with different frequencies. Simulation results show that for a 39-span system, the 4-core/fiber system with negligible crosstalk outperforms the single-core system by 2.2 dBQ₂₀. The impact of crosstalk between cores of a multi-core fiber (MCF) on the system performance is studied. The simulation results show that the performance of the multi-core WDM system is less sensitive to the crosstalk effect compared to conventional multi-core systems since the propagating channels in the cores are not correlated in frequency domain.</p> / Doctor of Philosophy (PhD)

The main aim of this work id to provide integral methods to predict and characterize the properties of composite structures based on hybrid polymers and reinforcements, that could lead to useful results from an industrial point of view. This is addressed, if possible, by theoretical predictions of the effective properties by using the available experimental data. The first part is focused on the scientific achievements of the author that allowed a quantitative characterization of the main effective properties of several composite architectures from hybrid polymers and reinforcements, based on bio matrices, tailor-made matrices and different theoretical and simulation methods using computer software to allow good comparison. The second part defines the future research lines to continue this initial investigation. The main objectives are clearly defined to give the reader a sound background with the appropriate concepts that are specifically discussed in the following chapters. As a main objective, this research work makes a first attempt to provide a systematic analysis and prediction of composite hybrid structures. / El objetivo general del trabajo es proporcionar medios integrales para predecir y caracterizar las propiedades de las estructuras de compuestos basados en polímeros y refuerzos híbridos, principales que pueden producir resultados de utilidad práctica simultáneamente. Esto se logra comparando, siempre que sea posible, las predicciones teóricas de las propiedades efectivas con los datos experimentales disponibles. Una primera parte se ocupa de los logros científicos del autor que permitieron caracterizar cuantitativamente las principales propiedades efectivas de las arquitecturas de compuestos basados en polímeros y refuerzos híbridos, basados en matrices bio, auto-desarrollados y diferentes métodos teóricos y de simulación por ordenador utilizados para la comparación. La segunda parte identifica las orientaciones futuras para la evolución y desarrollo de la ciencia y la investigación. Los objetivos generales fueron subrayados y concisos para dar al lector una visión previa de los conceptos que serán discutidos específicamente en los siguientes capítulos. Indirectamente, apuntan hacia uno de los objetivos principales de este trabajo, a saber, proporcionar una dirección para el análisis sistemático de materiales compuestos a base de refuerzos híbridos. / L'objectiu general d'aquest treball es proporcionar els mitjos integrals per tal de predir i caracteritzar les propietats d'estructures de compòsits basats en polímers i reforçaments híbrids, que poden produir resultats amb utilitat pràctica simultàniament. Aquest objectiu s'aconsegueix comparant, sempre que és possible, les prediccions teòriques de les propietats efectives amb les dades experimentals disponibles. Una primera part es centra en els temes científics en què ha treballat l'autor que han permès caracteritzar quantitativament les principals propietats efectives de les arquitectures de compòsits basades en polímers i reforçaments híbrids, derivats de matrius bio, auto-desenvolupats i diferents mètodes teòrics i de simulació informàtica per a una correcta comparació. La segona part identifica les orientacions futures per tal d'establir l'evolució i desenvolupament de la ciència i investigació lligada a la temàtica de la tesi. Els objectius generals han sigut clarament definits per tal de donar-li al lector una visió prèvia i sòlida dels conceptes que es discuteixen en capítols venidors. Indirectament, apunten cap a un dels objectius principals d'aquest treball, a saber, proporcionar una direcció per a l'anàlisi sistemàtica de materials compòsits a base de polímers i reforçaments híbrids. / Motoc, D. (2017). Development of green composites based on epoxidized vegetable oils (EVOs) with hybrid reinforcements: natural and inorganic fibers [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90399

Few mode fibers and multimode fibers (MMFs) are traditionally regarded as unsuitable for important applications such as communications and sensing. A major challenge in using MMFs for aforementioned applications is how to precisely control the waveguide modes propagating within MMFs. In this thesis, we experimentally demonstrate a generic method for controlling the linearly polarized (LP) modes within a two-mode fiber (TMF). Our method is based on adaptive optics (AO), where one utilizes proper feedback signals to shape the wavefront of the input beam in order to achieve the desired LP mode composition. In the first part of this thesis, we demonstrate the feasibility of AO-based mode control by using the correlation between the experimentally measured field distribution and the desired mode profiles as feedback for wavefront optimization. Selectively excitation of pure LP modes or their combinations at the distal end of a TMF are shown. Furthermore, we demonstrate that selective mode excitation in the TMF can be achieved by using only 5×5 independent phase blocks. Afterwards, we extend our AO-based mode control method to more practical scenarios, where feedback signals are provided by all-fiber devices such as a directional fiber coupler or fiber Bragg gratings (FBGs). Using the coupling ratio of a directional coupler as feedback, we demonstrate adaptive control of LP modes at the two output ports of the directional coupler. With feedback determined by the relative magnitude of optical power reflected by a FBG and the transmitted power, selective excitations of the LP01 and the LP11 modes are experimentally shown. As the final component of this thesis, we experimentally combine the AO-based mode control with time-division-multiplexing. By choosing reflected pulses with appropriate arrival time for mode control, we can selectively excite the LP11 mode at different FBG locations within the TMF, based on the ratio of optical signals reflected by FBGs in the TMF and the transmitted signal. Using two lasers set at the two FBG peak reflection wavelengths associated with the LP01 and the LP11 modes, we can accomplish AO-based mode control within a TMF by using only the reflection signals from the FBG. By using the ratio of the reflected signals of two lasers as feedback, we demonstrate selective excitation of almost pure LP01 or LP11 mode at the FBG location within the TMF. The method developed in this thesis is generic and can be extended to many other applications using appropriately chosen feedback signals. It is possible to generalize the AO-based mode control method to MMF as well. This method may find important applications in MMF-based communication, sensing and imaging et. al. in the future. / Ph. D.

Call number: LD2668 .T4 1979 G46 / Master of Science

The ability of wheat bran and oat hulls to bind copper and zinc using a new chromatographic technique was investigated and compared to a centrifugation method. Also investigated was the bioavailability of copper which had been exogenously bound to wheat bran then fed to mice and rats. Wheat bran bound 6 mg Cu/g fiber when pH was raised to 7. Less binding occurred at lower pHs. Seven mg of zinc bound to wheat bran at pH 5 while only a trace bound at pH less than 2. Oat hulls bound 3 mg Cu/g fiber at pH 5, and less than 1 mg of zinc bound per g of oat hull at pH 6. Binding for both fibers depended on the level of mineral added to the fiber slurry during incubation. But only wheat bran binding capacity was influenced by pH. The two methods used did not compare favorably, in all cases, to the amount of mineral bound to fiber. Copper when bound to wheat bran, was utilized in both species, with differences occurring between species was noted. Rats fed the copper bound diet compared favorably with rats fed the copper-adequate diet as determined by body weight, weight gain, heart weight, liver copper concentration and heart copper concentration. Mice, on the other hand showed similar liver and heart concentrations of copper for mice fed either the copper-bound diet or the copper-adequate diets. The in vitro results showed that binding of copper or zinc to wheat bran occurred at a pH similar to the intestinal pH and wheat bran binds more copper and zinc than oat hulls. Oat hulls may prove to be a better dietary fiber source for those people who need to increase their dietary fiber, because oat hulls do not appear to bind copper or zinc and would not likely impair their absorption. Although wheat bran had a high binding capacity for copper, this binding did not significantly inhibit copper absorption as determined in animal studies suggesting that fiber-mineral binding (at least for copper bound to wheat bran) does not cause mineral deficiency symptoms as claimed by many researchers.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The use of traditional telemetry decommutation equipment can be easily expanded to create a real-time pulse code modulation (PCM) telemetry data recorder. However, there are two areas that create unique demands where architectural investment is required: the PCM output stage and the storage stage. This paper details the efforts to define the requirements and limits of a traditional telemetry system when used as a real-time, multistream PCM data recorder with time tagging.

This dissertation begins with a study of some of the linear and nonlinear optical properties of composite materials consisting of CdSₓSe₁₋ₓ microcrystallites embedded in a host glass matrix. These studies investigate changes in absorption, refractive index and nonlinear response time under a variety of experimental conditions. The data demonstrates that this class of materials exhibit: a strong saturation of absorption due to band filling; a large n₂ which also saturates; response times which range from <100ps to many nanoseconds; and a permanent darkening and change of n₂ induced by extended exposure to high energy pulses. These measurements were used to identify the optimum sample of the semiconductor doped glasses to demonstrate an efficient degenerate four-wave mixing process within a planar waveguide. High quality single mode waveguides were fabricated from the semiconductor doped glass by K⁺-ion exchange. Four wave mixing was performed in the waveguide that produced a peak reflectivity of ≅.003, which is 8 orders of magnitude larger than that achieved previously in a similar experiment where CS₂ was used as the nonlinear medium.

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / A fiber optic event timing system was developed for the High Speed Test Track at Holloman Air Force Base, Alamogordo, NM. The system uses fiber optic sensors to detect the passage of rocket sleds by different stations along the track. The sensors are connected by fiber optic cables to an electronics package that records the event time to a resolution of 100 nanoseconds. By use of a GPS receiver as the timebase, the event time is stored to an absolute accuracy of 300 nanoseconds. Custom VMEbus boards were developed for the event timing function, and these boards are controlled by a programmable high speed sequencer, which allows for complicated control functions. Each board has 4 electro-optic channels, and multiple boards can be used in a VMEbus card cage controlled by a single board computer. The system has been tested in a series of missions at the Test Track.

Many properties of polymers can be affected by dissolving gases and supercritical fluids at high temperatures and pressures. Solubility and diffusivity are crucial parameters in polymer processing applications that indicates the content of gases and supercritical fluids in a polymer. Hence, different devices for measuring solubility and diffusivity have been researched, but most of the devices used today are very complex, expensive, and requires long experiment time. In this final thesis, the feasibility of fiber optic sensors as measurement devices for solubility and diffusivity of gas/SCF in polymers have been investigated. Many of the polymers used in polymer processing have high refractive index, from 1.40 to 1.60. However, most of the refractive index sensors based on fiber optics only operate in refractive index ranges of 1 to 1.44 because once the surrounding refractive index becomes greater than that of cladding, the total internal reflection is lost and only small portion of the light propagation occurs. This final thesis first reviews the current methods to measure solubility and diffusivity of gases and supercritical fluids in polymers. In addition, different types of fiber optics sensors used for sensing the refractive index are reviewed. Then, the thesis presents cost efficient, but effective fiber optic refractive index sensors, which are the silver nanoparticle coated LPG sensor, uncoated PCF MZI sensor, silver nanoparticle PCF MZI sensor, and the transmission intensity based gap sensor, to sense the surrounding refractive index in the region greater than the cladding, for the future application of solubility and diffusivity measurement. Moreover, future works that would help in sensing solubility and diffusivity of gas in polymers are also proposed. / Graduate

Carbon nanotubes have now been a subject of intense research for approaching two decades. Although a short time relative to most conventional materials, much hype about the intrinsic properties of this material has now been substantiated by experiment. The results are conclusive that carbon nanotubes are truly phenomenal materials with highly desirable mechanical, electrical and thermal properties. Furthermore, multiwall carbon nanotubes (MWNTs) have emerged as the most economically viable and abundant form of carbon nanotubes, and therefore the most likely candidate for application. The key materials engineering challenge remains in effectively transferring their properties to macro-scale materials in the form of composites. It is here that research merges with application. This dissertation has therefore been directed to focus on carbon nanotube composites in an applied sense. Here, the state of the art is reviewed, and experimental results of carefully selected composite systems, studied in detail for (1) mechanical, (2) electrical and (3) thermal properties, are presented and discussed. In terms of mechanical properties, the effects of MWNTs for augmentation of the tensile properties of PAN-based carbon fiber, and fatigue performance of poly(methyl methacrylate) are investigated and reported. In MWNT composite PAN-based carbon fiber, the formation of an ordered interphase layer sheathing the nanotubes was observed in fracture surfaces, which indicated a clear importance of their function to template the growth of carbon formation in the PAN-based matrix fiber. These structures open up a route to nano-scale tailorability of the crystallographic morphology of the composite fibers. Large improvements in fatigue performance were observed in MWNT/PMMA composites compared to MWNT/chopped carbon fiber composites, and attributed to the nanometer scale dimensions of the MWNTs enabling them to mitigate submicron damage such as polymer crazing. In terms of electrical and thermal properties, MWNT/epoxy composites were superior to MWNT/carbon black composites. Furthermore, extremely large improvements in the thermal conductivity of epoxy were observed for epoxy-infiltrated aligned MWNT arrays. The alignment of the MWNTs was shown to play a dominant role in enabling the improvement. Finally, these results, in concert with the literature are discussed in terms of the application of carbon nanotubes in engineering materials.