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1
Saravanos, Constantine. "Operational window of single-mode optical fibers." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10834.
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The purpose of this Ph.D. thesis is to define the design window of single-mode dispersion-unshifted fibers. This window, defined in the mode field diameter (MFD) and cutoff wavelength (lambda c) plot is determined by the fiber properties with regards to the chromatic dispersion, the bend loss sensitivity at 1550 nm and the modal noise penalty imposed on high speed operating systems. This has been achieved by developing numerical models used to analyze the properties of optical fibers. These models were used to calculate the propagation characteristics of optical fibers and from them their physical properties, such as the dispersion and bending loss of the fundamental mode. Similar programs, used in the calculations of the LP11 mode attenuation and bend performance, determined the fiber's modal noise sensitivity and from it the upper limit of cutoff wavelength.
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Niemi, David. "Coupling down converted light into single mode fibers /." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1827.pdf.
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Niemi, David A. "Coupling Down Converted Light Into Single Mode Fibers." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/893.
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We investigate the influence of the pump and collection mode parameters on the collection efficiency of Type I down converted photons into single mode fibers. For best single and coincidence counting rates, we find that the mode sizes should be close to the same size and that the mode waists should be located near the down-conversion crystal. Larger collection waists give higher collection efficiencies, but lower singles counts.
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Cheng, Yujie. "Mode Volume Reduction in Single Crystal Sapphire Optical Fibers." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77387.
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This research provides the original work on the geometry factors selection for single crystal sapphire optical fiber (SCSF) to improve the optical property in sensing applications. Single crystal sapphire fibers were fabricated with a Laser Heated Pedestal Growth (LHPG) system, which was constructed in-house at Virginia Tech. The cost effective, high efficiency and fully operational Laser-heated Pedestal Growth (LHPG) system as well as the fiber fabrication process were also demonstrated in this research. The results indicated the windmill single crystal sapphire optical fiber (SCSF) will readily improve the performance of current fiber optic sensors in the harsh environment and potentially enable those that are limited by the optical property of unclad single crystal sapphire optical fiber (SCSF).<br>Ph. D.
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Robinson, Risa J. "Polarization modulation and splicing techniques for stressed birefringent fiber /." Online version of thesis, 1995. http://hdl.handle.net/1850/12228.
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Lu, Liang-Ju. "Analysis and design of broadband single-mode multi-clad fibers." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54390.
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ln the last several years, considerable attention has been paid to the study of dispersion-flattened single-mode fibers which offer a high transmission capacity with low losses through a wide range of wavelengths. However, the existing designs are sensitive to bending and manufacturing tolerances, and are not truly single-mode at most wavelengths of interest.
To remedy these problems a new series of broadband dispersion-flattened truly single-mode fiber designs are proposed. These fibers have both dispersion-shifted and dispersion-flattened features with low splice and bend losses. Results demonstrating a total dispersion of ±0.97 ps/km-nm over the entire spectral range between 1.31 μm to 1.66 μm are presented. Such dispersion-flattening is achieved while simultaneously maintaining a mode-field radius of 3 μm to 5 μm in the dispersion-flattened wavelength range. The most significant achievement is that the proposed muIti-clad fiber design is strictly single-mode and splice and bend losses are smaller than those of double-clad, triple-clad, and quadruple-clad fibers with the same value of dispersion.
Ultralow dispersion fibers, whose chromatic dispersion and the first and second-order derivatives of the chromatic dispersion are zero at 1.5 μm or 1.55 μm, are described. This effectively increases the laser emission tolerance. Ultralow dispersion fibers open the way to wavelength multiplexing with currently available inexpensive multifrequency lasers, either in local or long distance networks. These fibers also have low splice and bend losses compared to double-clad, triple-clad, and quadruple-cIad fibers.
An inverse waveguide synthesis program, which can trace multiple objective functions and optimize multiple parameters simultaneously, is developed. An objective function is applied, for the first time, to optimize the dispersion-flattened single-mode fiber index profile with respect to: (1) minimum dispersion, (2) the wavelengths of zero-dispersion, (3) maximum width of dispersion-flattened window, (4) maximum layer index difference less than 0.8%, and (5) layer thickness larger than 3.5 μm.
The accuracy of chromatic dispersion calculations in dispersion-flattened fibers is evaluated. lt has been shown that the accuracy of approximate methods is influenced not only by the index differences, but also by their derivatives with respect to wavelength.
The matrix method and direct numerical integration of the wave equation are used to compute the mode propagation constants, cutoff frequencies, field distributions, mode-field radius, and splice loss, and carry out production tolerance analysis for multi-clad step-index fibers and graded-index fibers, respectively. Detailed analysis and optimized fiber data are presented.<br>Ph. D.
7
Zhou, Shun Hua. "Photo-induced birefringence in single-mode optical fiber." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07112009-040515/.
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Thompson, John Russell. "Multiple four-wave mixing processes in single-mode optical fiber." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/30955.
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Jiang, Jingwen. "Vector mode analysis of dispersion-shifted single-mode triangular-index fibers with a trench." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59953.
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A vector mode analysis of dispersion-shifted-mode triangular-index fibers with a trench is presented. The aspects considered are the total dispersion, splice losses and bending loss of such fibers as a function of the trench width and location, wavelength fluctuations, index difference, as well as core radius change. The presence of a trench has pronounced effects on the performance of these fibers, yielding combined advantages of dispersion-shifted and dispersion-flattened fibers, and also improves the splice loss and bending loss characteristics. Some fiber characteristics due to the presence of a trench found in this study are interesting and have not been noted previously. As for the fabrication aspect, the effects of the parameter variations on the fiber performance are examined in detail.<br>Unlike other authors' results obtained using the scalar modal fields, our formulas here derived from the vector modal fields facilitate the study of the polarization dependence of the splice and bending losses. For weakly guiding fibers with a small index gradient, the polarization dependence becomes negligible.
10
Nasta, Manish H. "Loss phenomena in perturbed single-mode optical fibers : investigation and applications /." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06112009-064004/.
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Bechter, Andrew, Jonathan Crass, Ryan Ketterer, et al. "On-sky single-mode fiber coupling measurements at the Large Binocular Telescope." SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/622009.
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The demonstration of efficient single-mode fiber (SMF) coupling is a key requirement for the development of a compact, ultra-precise radial velocity (RV) spectrograph. iLocater is a next generation instrument for the Large Binocular Telescope (LBT) that uses adaptive optics (AO) to inject starlight into a SMF. In preparation for commissioning iLocater, a prototype SMF injection system was installed and tested at the LBT in the Y-band (0.970-1.065 mu m). This system was designed to verify the capability of the LBT AO system as well as characterize on-sky SMF coupling efficiencies. SMF coupling was measured on stars with variable airmasses, apparent magnitudes, and seeing conditions for six half-nights using the Large Binocular Telescope Interferometer. We present the overall optical and mechanical performance of the SMF injection system, including details of the installation and alignment procedure. A particular emphasis is placed on analyzing the instrument's performance as a function of telescope elevation to inform the final design of the fiber injection system for iLocater.
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Rains, Adam D., Michael J. Ireland, Nemanja Jovanovic, et al. "Precision single mode fibre integral field spectroscopy with the RHEA spectrograph." SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/622808.
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The RHEA Spectrograph is a single-mode echelle spectrograph designed to be a replicable and cost effective method of undertaking precision radial velocity measurements. Two versions of RHEA currently exist, one located at the Australian National University in Canberra, Australia (450 - 600nm wavelength range), and another located at the Subaru Telescope in Hawaii, USA (600 - 800 nm wavelength range). Both instruments have a novel fibre feed consisting of an integral field unit injecting light into a 2D grid of single mode fibres. This grid of fibres is then reformatted into a 1D array at the input of the spectrograph (consisting of the science fibres and a reference fibre capable of receiving a white-light or xenon reference source for simultaneous calibration). The use of single mode fibres frees RHEA from the issue of modal noise and significantly reduces the size of the optics used. In addition to increasing the overall light throughput of the system, the integral field unit allows for cutting edge science goals to be achieved when operating behind the 8.2 m Subaru Telescope and the SCExAO adaptive optics system. These include, but are not limited to: resolved stellar photospheres; resolved protoplanetary disk structures; resolved Mira shocks, dust and winds; and sub-arcsecond companions. We present details and results of early tests of RHEA Subaru and progress towards the stated science goals.
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Chiarello, Fabrizio. "Analysis and application of nonlinear amplification effects in single-mode optical fibers." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423797.
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This thesis focuses on all-optical signal generation and processing through nonlinear amplification phenomena in single-mode fibers.
Three different nonlinear fiber optical oscillators are investigated and experimentally demonstrated. A continuous-wave pump for fiber Raman amplifiers, developed with the goal of achieving high degree of polarization, tunability and suppression of stimulated Brillouin scattering, is presented, discussed and used to achieve nonlinear polarization attraction. A fast and widely tunable fiber optical oscillator based on stimulated Raman scattering and on broad- and narrow-band fiber optical parametric amplification, and exploiting the time-dispersion-tuning technique, is demonstrated and characterized. Each nonlinear effect dominates in a different spectral region, so that the fiber optical oscillator achieves a tuning range of 160 nm. Through the same time-dispersion-tuning method, a fast tunable optical frequency comb, based on cascaded four-wave mixing, is obtained by using a single pump, avoiding the limitations in spectral purity and frequency and phase stability given by double pump systems.
Finally, the control of the state of polarization and of the degree of polarization through nonlinear polarization attraction in counter-propagating fiber Raman amplifiers in standard, randomly birefringent, single-mode fibers is studied, analyzed and characterized. The analysis, including the effects of pump depletion, nonlinear polarization rotation and orthogonal Raman gain, shows that counter-propagating fiber Raman amplifiers are effective in attracting the signal toward a predetermined state of polarization settled by the pump input state of polarization. Moreover, the importance of the role of pump depletion in achieving signal repolarization in fibers with moderately-high polarization-mode dispersion is discussed. The performances and the limits of repolarization efficiency are determined, leading to a quantitative relationship between the degree of polarization and the gain of the fiber Raman amplifier, which is then confirmed to represent an upper bound on the maximum achievable degree of polarization.<br>Questa tesi è focalizzata sulla generazione e sull’elaborazione completamente ottiche di segnali attraverso fenomeni di amplificazione non lineare in fibre ottiche a singolo modo.
Tre diversi oscillatori non lineari in fibra ottica sono investigati e dimostrati sperimentalmente. Una pompa ad onda continua per amplificatori Raman in fibra, sviluppata con l’obiettivo di ottenere un alto grado di polarizzazione, sintonizzabilità e soppressione dell’effetto Brillouin, è presentata, discussa e utilizzata al fine di ottenere attrazione di polarizzazione non lineare. Un oscillatore in fibra ottica con sintonia veloce su un’ampia banda basato sugli effetti di amplificazione Raman e di amplificazione parametrica a banda stretta e a banda larga, che sfrutta la tecnica di sintonia mediante dispersione temporale (time-dispersion tuning), è dimostrato e caratterizzato. Ciascuno degli effetti non lineari domina in una diversa regione spettrale, cosicché l’oscillatore raggiunge un intervallo di sintonia di 160 nm. Attraverso lo stesso metodo di sintonia mediante dispersione temporale, un comb ottico in fibra con sintonia veloce, basato sull’effetto di miscelazione a quattro onde a cascata, è ottenuto usando una singola pompa, evitando così i limiti di purezza spettrale e di stabilità di frequenza e di fase dei sistemi a doppia pompa.
Infine, il controllo dello stato e del grado di polarizzazione, attraverso l’attrazione di polarizzazione non lineare in amplificatori Raman in fibra ottica standard con birifrangenza aleatoria, è studiato, analizzato e caratterizzato. L’analisi, che include gli effetti di svuotamento della pompa, della rotazione non lineare di polarizzazione e di guadagno Raman ortogonale, mostra che gli amplificatori Raman contro-propaganti sono efficaci nell’attrarre il segnale verso uno stato di polarizzazione predeterminato e imposto dallo stato di polarizzazione di ingresso della pompa. Viene inoltre discussa l’importanza del ruolo dello svuotamento della pompa nell’ottenere la ripolarizzazione del segnale in fibre con dispersione dei modi di polarizzazione moderatamente alta. Le prestazioni e i limiti dell’efficienza di ripolarizzazione vengono determinati portando ad una relazione quantitativa tra il grado di polarizzazione e il guadagno dell’amplificatore Raman, relazione che rappresenta un limite superiore sul massimo grado di polarizzazione raggiungibile.
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KOSA, NADHIR BAHJAT. "NEW INTERFEROMETRIC METHOD FOR MEASURING CHROMATIC DISPERSION IN SINGLE MODE FIBERS (FOURIER TRANSFORM)." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184171.
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A new interferometric method which indirectly measures the total chromatic dispersion of a single mode fiber is demonstrated. The technique utilizes a short length of fiber, an unmodulated broadband source, simple low frequency electronics, and a standard interferometer. The concept of this measurement is based on the behavior of the uncorrelated individual bursts of light from the elemental emitters that constitute a thermal source. Their propagation through a dispersive media, e.g., silica fiber, which is placed in one arm of the interferometer, is delayed and broadened. They will interfere with their counterpart from the other arm, generating a train of time-varying fringes as one mirror of the interferometer is uniformly translated. The local frequency of the fringes at a given position of the moving mirror is a direct measure of the instantaneous wavelength, while the mirror position itself demarks the corresponding relative delay. A colinearly launched HeNe laser beam is used as a reference to calibrate the other source's fringe width and location of the mirror. In this experiment, an edge-emitting LED of λo = 830 nm and Δλ = 60 nm was used. The tested fibers had a length of 27.9 cm and 38.3 cm, which made the width of the crosscorrelation function approximately 100 times greater than the source's coherence length. The speed of the mechanically driven mirror set the frequency of the HeNe fringes to approximately 800 Hz with an r.m.s. fluctuation around the mean of 0.2%. The SNR of the HeNe fringes was four times larger than the LED's. Ten different runs for each fiber were executed. Data from the two sets of simultaneous measurements of delay versus wavelength were used to fit the best linear and quadratic polynomials with a minimum residual mean error square. The derivative of this function with respect to wavelength gave the dispersion relation. The accuracy of measured delay and wavelength were 0.1 ps and 6 nm, respectively. The dispersion value and its standard error for the best linear fit was approximately 117 ∓ 2 ps/km nm. The standard error for the quadratic fit was much larger due to the high noise level accompanying signal. A thorough investigation of the noise sources, accuracies, standard error of the polynomial's coefficient, and SNR analysis is conducted. This measurement is simple and has the potential of achieving substantially higher accuracy--especially for the longer wavelength region where dispersion is minute.
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Apriyanto, Haris. "Study, analysis and experimental validation of fiber refractometers based on single-mode, multimode and photonic crystal fibers for refractive index measurements with application for the detection of methane." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0022.
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La mesure de l'indice de réfraction a été étudiée depuis qu'Ernest Abbé aie initialement conçu un réfractomètre en 1869, appelé le réfractomètre d'Abbé. Depuis lors, de nombreux réfractomètres ont été développés tels que le réfractomètre à prisme optique ainsi que le réfractomètre à fibre optique, en raison de leurs applications étendues pour la détection de divers paramètres physiques, biologiques et chimiques. Récemment, un grand nombre de chercheurs ont mis au point des réfractomètres basés sur des fibres optiques, exploitant des mécanismes tels que la résonance des plasmons de surface (SPR), les interférences multimodes, les fibres à réseaux de Bragg (FBG), les fibres à réseaux à longues périodes (LPG), les fibres optiques coniques et la fibre multimode à gaine dénudée. Les capteurs fibrés sont avantageux grâce à leur immunité contre les interférences électromagnétiques, passivité électrique au niveau de la sonde de détection et potentiel de mesure in situ à long terme. Cette thèse concerne le développement de modèles complets fonctionnels et précis pour les réfractomètres à fibres optiques basés sur la modulation d'intensité optique, en particulier la réfractométrie à fibre multimode à gaine dénudée ainsi que les systèmes hybrides associant fibres monomode et multimode, et un réfractomètre hybride tout fibré utilisant des fibres à cristaux photoniques. L'objectif clé de ce travail est de caractériser les performances de ces réfractomètres à fibres optiques basés sur la modulation d'intensité en termes de réponse en puissance, de sensibilité, de résolution et de dynamique de mesure. Les résultats de simulation qui sont corroborés expérimentalement démontrent que la très grande sensibilité obtenue dans la zone II (c'est-à-dire le régime de détection typiquement utilisé pour mesurer l'indice du milieu supérieur à l'indice de gaine mais inférieur ou égal à l'indice du coeur) pour tous les trois réfractomètres. Cependant, la sensibilité dans la Zone (c’est-à-dire le régime de détection pour lequel l’indice du milieu à mesurer est supérieur à celui du coeur) est très faible. Ainsi, un refractomètre fibré hybride monomode-multimode est utilisé pour améliorer la sensibilité dans la Zone III. D'autre part, la sensibilité pour la zone I (c'est-à-dire le régime de détection pour mesurer l’indice du milieu inférieur à l'indice de la gaine) a été améliorée en augmentant l'absorption des ondes évanescentes à l'aide du réfractomètre hybride tout fibré à base de fibres à cristaux photoniques à coeur solide. En termes d'application réelle du réfractomètre à fibre pour la détection biochimique, une preuve de concept pour un capteur du gaz méthane a été démontrée en utilisant les supramolécules de cryptophane-A qui permettent de piéger les molécules du méthane. Le cryptophane-A incorporé dans un film hôte à base de styrène acrylonitrile (SAN) est appliqué sur la zone dénudée du capteur comme une région fonctionnalisée. L'indice de réfraction de cette couche sensible augmente proportionnellement avec l'augmentation de la concentration du méthane, ce qui induit une variation de la puissance optique transmise dans le capteur fibré<br>Refractive index measurement has been studied since Ernest Abbé initially designed a refractometer in 1869, which is named the Abbé refractometer. Since then, numerous types of refractometers have been developed by employing either the optical prism-based refractometer or the optical fiber-based refractometer, due to their wide-ranging applications such as for sensingvarious physical, biological and chemical parameters. Recently, a large number of researchers have been developing refractometers based on optical fibers, exploiting mechanisms such as surface plasmon resonance (SPR), multimode interference, fiber Bragg gratings (FBG), long period gratings (LPG), tapered optical fibers, and striped-cladding multimode fibers (MMF), for their advantages in immunity against electromagnetic interference, electrical passivity at the sensing probe, and capability to long term in-situ measurement. This thesis concerns the development of comprehensively functional and accurate models for optical fiber refractometers based on optical intensity modulation, in particular for stripped-cladding MMF refractometry as well as hybrid systems involving a combination of single-mode-multimode fiber refractometery and the all-fiber hybrid refractometer using photonic crystal fibers. A key objective of this work is to characterize the performance of these intensity-based optical fiber refractometers in terms of their power response, sensitivity, resolution, and dynamic range. The simulation results which are corroborated experimentally demonstrate very high sensitivity being obtained in Zone II (i.e. the sensing regime typically employed for measuring a sensing medium index higher than the cladding index but less than or equal to the core index) for all three types of refractometers. However, the sensitivity in Zone III (i.e. the sensing regime for which the sensing medium index is higher than the core index) is very low. A hybrid single-mode fiber - multimode fiber configuration is used to improve the sensitivity in Zone III. On other hand, the sensitivity for Zone I (i.e. the sensing regime typically employed for measuring a sensing medium index lower than the cladding index) has been improved by increasing evanescent wave absorption using the all-fiber hybrid refractometer based on solid-core photonic crystal fibers. As a further potential of the fiber refractometer for applications in biochemical sensing, the proof-of-concept for a methane gas sensor has been demonstrated using supramolecular cryptophane-A which enables to trap the methane molecules. Cryptophane-A incorporated into a functionalized film of StyreneAcrylonitrile (SAN) host is applied to a de-cladded region of the sensor as the sensitive region. The refractive index of this functionalized layer increases proportionally with increasing methane concentration, subsequently inducing variations in the transmitted optical power along the fiber sensor
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Shang, Alain. "Effects of acoustic properties on stimulated backward brillouin scattering in single mode optical fibers." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61056.
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The acoustic characterization of six glasses each doped with one of the following dopants: GeO$ sb2$, P$ sb2$O$ sb5$, F, TiO$ sb2$, B$ sb2$O$ sb3$ or Al$ sb2$O$ sb3$ is presented. We have found that a linear variation of acoustic velocities versus dopant concentration for each dopant studied and the addition of Al$ sb2$O$ sb3$ increases the acoustic velocity while all the other dopants decrease this velocity. In addition, the acoustic velocity variation is more sensitive than the optical refractive index to the dopant concentration for the doped silica glasses investigated. Furthermore, the F and GeO$ sb2$ doped silica glasses exhibit higher acoustic loss than pure fused silica does.<br>These six doped glasses are widely used as core and cladding material for optical fibers. Their acoustic properties can affect the backward stimulated Brillouin scattering since this scattering involves acoustic disturbances of the material. The SBBS threshold is evaluated theoretically taking the Bragg and the nonlinear coupling of the pump and Stokes into account.<br>Effects of different acoustic profiles of SMOFs on SBBS are experimentally investigated. (Abstract shortened by UMI.)
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Arabasi, Sameer. "Tapered Splice for Efficient Power Coupling to Small-Core Nonlinear Fibers." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28383.
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There is continued interest in nonlinear devices for different types of optical signal processing, such as Raman or parametric amplifiers. The small nonlinearity of conventional single-mode fibers sets a major limitation for these devices. A large nonlinearity can be achieved by having a large nonlinear coefficient, a small effective area, or both. Having a small effective area, however, requires efficient coupling to very small
core fibers.
A novel technique for splicing conventional single-mode fibers to small core fibers is proposed and demonstrated. The coupling efficiency obtained by this technique is considerably improved over that obtained by the butt-joint splice. This technique uses a highly
tapered splice in which the field leaves the core and propagates as a fundamental cladding mode before it couples back to the core mode
of the small core fiber. At the beginning of the taper the fundamental core mode carries most of the power. Over the down-taper region, the core mode couples to the fundamental cladding mode for
which the cladding-air interface plays a major role in guiding the light. Over the up-taper region, the cladding mode is coupled back
to the core mode. Fabrication of such a device involves many constraints. Alignment of the cores, the slope of the taper, and the
taper length are important issues to ensure that excessive radiation loss does not take place.
The theory of tapered single-mode fiber is discussed including adiabaticity criteria, length considerations, mode coupling and wavelength dependence. We use a computational simulation to examine how the field changes from one part of the taper to the other. Variations of the fiber and the field properties along the taper are
studied. In this simulation, the tapered region is approximated as a sufficiently large number of cascaded uniform fiber segments of decreasing or increasing diameters. Another analysis based on the conservation of power flow is also provided.
Tapered splices were fabricated using two different experimental setups. The experimental setup to verify our theoretical results is shown. The tapering process is thoroughly discussed. The spectrum of a tunable laser passing through a splice shows how modes interact with each other during the tapering process. We successfully fabricated very low loss tapers with extremely small diameters. Tapered splices showed a lower loss than their butt-joint counterparts. Experimental measurements of these tapered splices are presented and discussed.<br>Ph. D.
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Elliott, Timothy John. "Chromatic dispersion measurement in single-mode optical fibers by acousto-optic modulation and phase detection." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/101274.
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A system to measure chromatic dispersion in single-mode optical fibers with near point wavelength resolution is described. Differential propagation constant data for the test fiber is collected by using an acousto-optic modulator to frequency-shift laser light passed to an optical heterodyne. Theoretical developments include a frequency-domain calculation technique for interpreting empirical results. The system is proven infeasible, however, due to inherent noise sensitivity<br>M.S.
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SOUZA, KAROLINE DE. "IMPACT OF THE EFFECTS OF PMD IN THE LIGHT POLARIZATION CONTROL IN SINGLE-MODE FIBERS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=35252@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>Este trabalho apresenta o estudo e a realização de experimentos a fim de investigar os efeitos da PMD (Polarization Mode Dispersion) no controle de polarização implementado em um enlace de fibra óptica monomodo. Esse estudo permitirá a otimização de controladores de polarização em sistemas de transmissão que venham a utilizar multiplexação em polarização (PolMux) combinado a técnicas de UDWDM (Ultra Dense Wavelength Division Multiplexing), possibilitando o aumento da taxa de transmissão em um canal. Para tanto, foram realizadas medidas experimentais que demonstrem o desvio angular da polarização devido à descorrelação entre canais, através da análise da evolução da polarização do sinal óptico em função da PMD, do comprimento de onda e do espaçamento espectral; foram analisadas duas propostas para se utilizar no controle de polarização; estatísticas referentes à atenuação dos canais utilizados foram realizadas e também o cálculo da correlação com intuito de analisar como esses canais se relacionam.<br>This work presents the study and conducting experiments to investigate the PMD (Polarization Mode Dispersion) effects in polarization control implemented in a single-mode fiber optic link. This study will allow the optimization of polarization controllers in transmission systems that will use polarization multiplexing (PolMux) combined with techniques like UDWDM (Ultra Dense Wavelength Division Multiplexing), and thereby to increase the transmission rate in a channel. Therefore, we performed experimental measurements showing the angular displacement of the polarization due to decorrelation between channels by analyzing the evolution of the polarization of the optical signal as a function of PMD, wavelength and the spectral spacing, analyzed using two proposals for the control of polarization, statistics of the fading channels used and also performed the calculate the correlation with the aim to analyze how these channels are related.
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Cui, Ziruo. "Wet Etching Optical Fibers to Sub-micron Diameters for Sensing Application." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1397801129.
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Johal, Sukhvinder Singh. "Second harmonic generation in Langmuir-Blodgett waveguide overlays coated onto single-mode optical fibres." Thesis, Cranfield University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340876.
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Darwich, Dia. "Gestion des effets thermiques dans des fibres actives à très grande aire modale pour la montée en puissance des sources laser à 2μm". Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0085/document.
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Ce travail concerne le développement d’une fibre optique à structure originale permettant la montée en puissance moyenne et crête dans les systèmes lasers à 2μm. La gestion des effets thermiques est devenue aujourd’hui un enjeu primordial notamment pour essayer de repousser le seuil d’apparition des instabilités modales transverses. Le principe mis en avant ici est basé sur la rupture de symétrie de la gaine microstructurée de la fibre afin d’améliorer la délocalisation des modes d’ordre supérieur vers l’extérieur du milieu à gain. Ainsi une propagation quasi-monomode est obtenue dans une fibre apériodique passive avec un coeur de 140μm à 2μm. Un travail de modélisation a été mené de manière à proposer d’autres structures basées sur une modulation contrôlée de l’indice de réfraction dans le milieu à gain afin de repousser encore plus le seuil du régime multimode. En outre, la fabrication de la première fibre dopée thulium à large aire modale (Dcoeur = 18μm) par la méthode REPUSIL a montré une efficacité de 50%. Ensuite, la fabrication de la première fibre rigide complètement apériodique à gaine réduite dopée thulium a été réalisée. Une fibre avec un coeur de 29μm et un diamètre extérieur de 769μm et une longueur de 86cm a été caractérisée en configuration laser et a permis d’obtenir une émission laser à 2μm de 3,8W (puissance limitée par la puissance de la diode de pompe disponible) avec un rendement de 20% et une qualité de faisceau quasi-monomode. De plus, une fibre passive complètement apériodique à polarisation unique avec un coeur de 140μm a également été réalisée et a permis d’obtenir un ratio d’extinction de polarisation de 16,5dB à 2μm<br>This work deals with the development of an original leaky structure of optical fiber aiming at generating a high power laser radiation at 2μm in CW and pulsed regimes. The management of thermal effects in high power/energy regime became a major issue, in particular to push further the transverse modal instabilities threshold. Our approach consists in breaking the symmetry of the microstructured fiber cladding for to improve the delocalization of the high order modes outside of the gain medium. Thus, an effective single-mode propagation at a 2μm operating wavelength was first demonstrated into a passive aperiodic fibers whose the core diameter reaches up to 140 μm. After implementing some Stress Applying Parts over our aperiodic design, a PER of 16.5dB was achieved at 2μm using a single polarization passive FA-LPF with a core of 140 μm. Thence, a numerical study on the tailoring the active core refractive index has been carried out so as to fend off the threshold of multimodedness. Additionally, the first LMA Tm-doped fiber (Dcoeur = 18μm) fabricated by the REPUSIL method and showing an efficiency of 50% is demonstrated. Thereafter, the fabrication of the first rod-type Tm-doped FA-LPF with reduced cladding is shown. A 29 μm core FA-LPF was characterized in laser configuration, leading to an effective single-mode emission of 3.8W of average power at 2μm strictly restricted by the available pump power and an efficiency of 20%
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Martinez, Pinon F. "Characterizing single-mode fibres and single-mode fibre lenses." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383403.
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Wood, Thomas W. Jr. "Evaluation of Single-Mode and Bragg Grating Optical Fibers Interrogated with an Optical Backscatter Reflectometer (OBR) in High Temperature Environments for Advanced Instrumentation in Nuclear Reactors." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1373364266.
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Blake, Bryan P. "Initial Testing of Single-Mode Optical Fibers Interrogated with an Optical Backscatter Reflectometer at High Temperatures and in Radiation Environments for Advanced Instrumentation in Nuclear Reactors." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1344873713.
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Hale, Zoe Miranda. "Fibre optic sensors using adiabatically tapered single mode fibres." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320155.
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Brainis, Edouard. "Utilisation de l'optique fibrée pour l'ingénierie quantique: du support passif aux sources." Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210806.
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La dissertation explore différentes applications des fibres optiques en ingénierie quantique. Deux thématiques sont développées :d'une part l'utilisation des fibres optiques monomodales en silice pour l'implémentation d'algorithmes et de protocoles de communication quantiques et d'autre part l'utilisation de la non-linéarité de ces fibres pour réaliser des sources de paires de photons corrélés. L'étude est à la fois théorique et expérimentale./ The dissertation explores various uses of optical fibers for quantum engineering. Two topics are developed :first the use of single-mode silica fibers for implementing quantum algorithms and communication protocols, second the use of these fibers for generating correlated photon-pairs.<br>Doctorat en sciences appliquées<br>info:eu-repo/semantics/nonPublished
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Fu, Shijie, Guannan Shi, Quan Sheng, et al. "Dual-wavelength fiber laser above 2 mu m based on cascaded single mode-multimode-single mode structures." IEEE, 2016. http://hdl.handle.net/10150/622786.
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A stable dual-wavelength Tm:Ho co-doped fiber laser operating above 2 mu m based on cascaded single mode-multimode-single mode (SMS) all-fiber structures has been proposed and experimentally demonstrated for the first time.
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Fosuhene, Samuel Kofi. "Single-end reflectometric measurements of polarization-mode dispersion in single-mode optical fibres." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/6280.
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In this thesis two novel single-end methods are applied to measure and characterize polarization mode dispersion in single mode optical fibres. Polarization mode dispersion (PMD) is an important factor negatively affecting the successful implementation of high speed long haul optical fibre networks operating at bit rates of 10Gb/s and above. PMD measurements are thus important for quality control during manufacturing and cabling processes. It is also useful for network operators planning to upgrade bitrates in existing networks to 10Gb/s and beyond. In an optical fibre link, sections with particularly high PMD may act to increase the entire PMD of the link. Identifying and replacing such sections can greatly reduce the PMD of the link. PMD measurements can be forward or single-end. In forward measurements, both ends of the fibre are used for input and detection. In single-end configuration, only one end of the fibre is used. For this reason, single-end measurements are more practical for the field where fibre ends are situated several kilometres apart. Single-end techniques can be implemented with a continuous wave for non-local PMD measurements (by Fresnel reflection). If a pulsed wave is used, local measurements can be achieved (by total power due to Rayleigh scattering). Two single-end schemes, one based on Fresnel reflection and the other due to Rayleigh scattering have been applied to measure non-local and local PMD of standard single mode optical fibres. For the non-local PMD measurements, the general interferometric technique (GINTY) was modified to operate in a round-trip configuration. In this configuration, the fibre was treated as a concatenation of two identical fibre segments. Three different sets of fibres were investigated, each set representing a particular mode coupling regime. For polarization maintaining fibres, (PMFs), with no mode coupling, a factor of two was found between forward and single-end measurements. For long single mode fibres in the long length regime, the factor was 1.4. For a combination of PMF and single mode fibres, a factor of 1.6 was obtained. The method which is accurate, repeatable, low cost and robust is very suitable for field applications. The second method is the polarization optical time domain reflectometric (P-OTDR) technique. This technique performs local birefringence measurements by measuring the evolution of the states of polarization (SOP). The birefringence information from such measurements was extracted and analysed to characterise four different fibres. Beat lengths and correlation lengths extracted from the P-OTDR were used to calculate the differential group delay (DGD) of the fibres. Next an expression for the root-mean-square differential group delay was derived and applied to the birefringence measurements to calculate the DGDs at a single wavelength. This method which operates at a single wavelength has a huge advantage. Firstly it is able to measure completely all the fibre characteristic parameters. Secondly it can measure mean DGD, root mean square DGD and instantaneous DGD. A plot of instantaneous DGD vs. length enables one to identify and eliminate sections with particularly high DGD. Finally since the P-OTDR system operates with a single wavelength, real time monitoring of PMD is possible via multiplexing. The results obtained are repeatable, accurate and are in good agreement with the standard Jones Matrix Eigenanalysis (JME) technique.
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Minelly, John D. "Field access techniques for single-mode fibres." Thesis, University of Southampton, 1989. https://eprints.soton.ac.uk/396389/.
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This thesis reports on the exploitation of the beam-expanding properties of tapers in single-mode fibres and on the development of a new and versatile approach to fibre polishing. A theoretical study of the fused-taper coupler explains the differences in coupling and polarisation characteristics of strongly-fused and weakly-fused couplers in terms of the difference in tunnelling capability of TE and TM polarised waves. A study of the application of glass capillary overjackets in the production of stable taper-based devices resulted in the realisation of the first practical tapered beam-expander for single-mode fibres and a class of couplers in which cut-off of the LP11 mode of the composite waveguide comprising the coupler waist induced a flattening of the wavelength characteristics of splitting ratio. The operational principles and fabrication of a single-mode fibre beam-splitter is described. This new device which operates as a LP01 mode transformer exhibits wavelength independent 50:50 power splitting. A new polishing technique in which the optical fibre is polished on a motor driven polishing wheel is reported. The polishing can be completed in less than ten minutes and polished lengths of up to 40mm are easily attainable. The technique was successfully applied to the construction of spectrally broad fibre polarisers.
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Weber, Thomas. "Powerful diode-pumped single-mode fiber lasers /." [S.l : s.n.], 1995. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Grimsley, Jonathan Scot. "Light Loss In Single Mode Fiber Optical Switches." Master's thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/37142.
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Light loss in single mode fiber optical switches is investigated. Loss due to reflection, aberration and fiber misalignment are evaluated. A simple model of image to fiber end face overlap for the fiber/lens system is developed. The intensity distribution of light in the fiber and imaging system is assumed to be gaussian. It was found that aberration is a major cause of loss and that fiber misalignment did not cause as much loss as expected. Loss due to reflection is assumed to be minimal due to the presence of anti-reflection coatings on the optical components.<br>Master of Science
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Fickers, Jessica. "Modulation formats and digital signal processing for fiber-optic communications with coherent detection." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209204.
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A débit de données élevé, typiquement supérieur à 10 Gsymboles/s, les lignes de<p>télécommunication optique à fibre monomode souffrent de façon accrue des distorsions<p>inhérentes à la fibre et à l’architecture de transmission. Nous pouvons classer les<p>effets de fibre en plusieurs catégories:<p>– Les effets linéaires. La dispersion chromatique est entraînée par la dépendance en<p>fréquence de l’indice de réfraction de la fibre. Il en résulte un élargissement des<p>bits optiques. La dispersion des modes de polarisation prend son origine dans<p>la biréfringence de la fibre. La modélisation de cet effet est compliquée par son<p>caractère stochastique et variable dans le temps.<p>– Les effets non linéaires prennent leur origine dans un indice de réfraction de<p>fibre qui dépend du champ optique. Ces effets peuvent être classés en deux<p>catégories. Premièrement, les effets intérieurs à un canal dont le plus influant<p>est l’automodulation de phase qui découle de l’effet Kerr optique :l’intensité<p>d’une impulsion lumineuse influence sa propre propagation. Deuxièmement, il<p>existe des conséquences de l’effet Kerr par lesquelles les différents canaux, se<p>propageant au sein de la même fibre, s’influencent mutuellement. Le phénomène<p>le plus influent parmi ces derniers est la modulation de phase croisée :l’intensité<p>d’un canal influence la propagation dans un canal voisin.<p>– Les pertes par diffusion Rayleigh sont compensées par les amplificateurs distribués<p>le long de la ligne de transmission. L’amplification optique par l’intermédiaire<p>d’émission stimulée dans des dispositifs dopés aux ions Erbium est<p>accompagnée d’émission spontanée amplifiée. Ceci entraîne la présence d’un<p>bruit blanc gaussien se superposant au signal à transmettre.<p>– La gestion des canaux dans le réseau optique implique la présence dans les noeuds<p>du réseau de filtres de sélection, des multiplexeurs et démultiplexeurs.<p>Nous examinerons aussi les effets de ligne non inhérents à la fibre mais à l’architecture<p>de transmission. Les modèles de l’émetteur et du récepteur représentent les imperfections<p>d’implémentation des composants optiques et électroniques.<p>Un premier objectif est de définir et évaluer un format de modulation robuste aux<p>imperfections introduites sur le signal par la fibre optique et par l’émetteur/récepteur.<p>Deux caractéristiques fondamentales du format de modulation, determinants pour la<p>performance du système, sont étudiés dans ce travail :<p>– La forme d’ onde. Les symboles complexes d’information sont mis en forme par<p>un filtre passe-bas dont le profil influence la robustesse du signal vis-à-vis des<p>effets de ligne.<p>– La distribution des fréquences porteuses. Les canaux de communication sont<p>disposés sur une grille fréquentielle qui peut être définie de manière électronique<p>par traitement de signal, de manière optique ou dans une configuration hybride.<p>Lorsque des porteuses optiques sont utilisées, le bruit de phase relatif entre lasers<p>entraîne des effets d’ influence croisée entre canaux. En revanche, les limites des<p>implémentations électroniques sont données par la puissance des architectures<p>numériques.<p>Le deuxième objectif est de concevoir des techniques de traitement numérique du<p>signal implémentées après échantillonnage au récepteur afin de retrouver l’information<p>transmise. Les fonctions suivantes seront implémentées au récepteur :<p>– Les techniques d’estimation et d’égalisation des effets linéaires introduits par la<p>fibre optique et par l’émetteur et le récepteur. Le principe de l’égalisation dans<p>le domaine fréquentiel est de transformer le canal convolutif dans le domaine<p>temporel en un canal multiplicatif qui peut dès lors être compensé à une faible<p>complexité de calcul par des multiplications scalaires. Les blocs de symboles<p>émis doivent être rendus cycliques par l’ajout de redondance sous la forme d’un<p>préfixe cyclique ou d’une séquence d’apprentissage. Les techniques d’égalisation<p>seront comparées en termes de performance (taux d’erreurs binaires, efficacité<p>spectrale) et en termes de complexité de calcul. Ce dernier aspect est particulièrement<p>crucial en vue de l’optimisation de la consommation énergétique du<p>système conçu.<p>– Les techniques de synchronisation des signaux en temps/fréquence. Avant de<p>pouvoir égaliser les effets linéaires introduits dans la fibre, le signal reçu devra<p>être synchronisé en temps et en fréquence sur le signal envoyé. La synchronisation<p>est généralement accomplie en deux étapes principales :l’acquisition réalisée<p>avant de recevoir les symboles d’information don’t l’objectif est une première<p>estimation/compensation des effets de manière "grossière", le tracking réalisé en<p>parallèle à l’estimation des symboles d’information dont l’objectif est l’estimation<p>/compensation des effets de manière "fine". Les algorithmes d’acquisition et<p>de tracking peuvent nécessiter l’envoi d’informations connues du récepteur.<p>– Les techniques d’estimation et de compensation des imperfections de fonctionnement<p>de l’émetteur et du récepteur. Une structure de compensation des effets<p>introduits par les composants optiques et électroniques sera développée afin de<p>relâcher les contraintes d’implémentation de l’émetteur et du récepteur.<p>Etant donné la très haute cadence à laquelle les échantillons du signal sont produits<p>(plusieurs dizaines de Gech/s), une attention particulière est portée à la complexité de<p>calcul des algorithmes proposés.<br>Doctorat en Sciences de l'ingénieur<br>info:eu-repo/semantics/nonPublished
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Yataki, M. S. "Fused taper single mode fibre couplers." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383498.
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Gold, M. P. "A study of backscatter in single-mode optical fibres." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304275.
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Hodel, Walter. "Investigations of nonlinear effects in optical single mode fibres /." [S.l : s.n.], 1986. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Velayudhan, Nirmalkumar. "Analysis of Thermally Diffused Single Mode Optical Fiber Couplers." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/36771.
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The phenomenon of dopant diffusion as a viable means of coupler fabrication is
investigated. It is well known that the diffusion of dopants can improve the uniformity of
multimode star couplers manufactured by the fused biconical taper technique. The
theoretical basis for the same phenomenon in a single mode coupler is developed, on the
basis of the theory of diffusion and the Gaussian approximation for circular fibers.
A novel technique to manufacture and design single mode optical fiber couplers
with a minimization of the manufacturing complexity is demonstrated. Traditionally fused
biconical tapered couplers have been manufactured by twisting, fusing and elongating
optical fibers at elevated temperatures. Usually, high temperature oxy-hydrogen flames are
used for such purposes and some degree of skill is needed for a human operator. The
complexity of control procedures for automation of the process is greatly increased by the
fact that the tapering process is an integral part of the feedback loop. This can be eliminated
if a constant tension is maintained on the fibers in the heating process while heat is applied
uniformly from a source such as a platinum wire furnace. Since the refractive index
differentials responsible for the guiding phenomenon at optical frequencies are directly
dependent on concentration of dopants like fluorine and germania, radial diffusion of such
dopants causes the fiber cores that are heated in a platinum wire furnace to come closer
together. Such proximity leads to the phenomenon of evanescent field interaction or
coupling of optical power from one arm of the coupler to the other.
The time evolution of the coupling process can be predicted in theory. While initial
results are promising, the ability to automate the manufacture of couplers will be
successful only after greater control over the variables is established. It is the intention of
this work to understand the physics behind the mechanism as well as to prove the
feasibility of modeling real world phenomena under controlled conditions.<br>Master of Science
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Jones, Steven Lee. "Single mode optical fibre bend loss modelling." Thesis, Manchester Metropolitan University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264454.
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Gouveia, Neto Artur da Silva. "Femtosecond pulse generation and propagation in single-mode optical fibres." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47085.
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Yu, Nu. "Coupling of a semiconductor laser to a single-mode fiber." Full text open access at:, 1987. http://content.ohsu.edu/u?/etd,135.
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Bedö, Stefan. "Erbium doped single-mode fiber lasers: studies on saturation effects /." [S.l : s.n.], 1995. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Hill, William Cary. "Low Modal Volume Single Crystal Sapphire Optical Fiber." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/78792.
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This research provides the first known procedure for cleanly and consistently reducing the diameter of single-crystal sapphire optical fiber (SCSF) below the limits of standard production methods, including the first production of subwavelength-diameter optical fiber (SDF) composed of single-crystal sapphire. The first known demonstration of an air-clad single crystal sapphire optical fiber demonstrating single-mode behavior is also presented, and the single-mode cutoff wavelength and diameter are determined.
Theoretical models describing and predicting the optical behavior of low modal volume sapphire optical fibers are also presented. These models are built upon standard weakly-guiding optical fiber theory, which is found to be accurate once experimentally-determined properties of the SCSF are substituted for theoretical values.
Reduced modal dispersion is also observed in the form of decreased laser pulse broadening in reduced-diameter SCSF. The improvements in spatial resolution for distributed sensing systems such as Raman distributed temperature sensing are also predicted based on the measured decrease in pulse duration.
This research also provides an enhanced understanding of the etching behavior of sulfuric and phosphoric acids on sapphire surfaces, including the first reporting of etching rates and activation energies for a-plane sapphire surfaces. Morphological changes of sulfuric and phosphoric acids at and beyond the temperature ranges used in etching were also tested and discussed in detail, especially regarding their practical impact on observed etching behavior.
The demonstration of LMV single-crystal sapphire optical fibers enables the adaptation of numerous sensing schemes requiring low modal volume or single-mode behavior to be utilized in extreme environments.<br>Ph. D.
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Haran, Francis Martin. "Bend loss in buffered single-mode optical fibre." Thesis, Heriot-Watt University, 1995. http://hdl.handle.net/10399/768.
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Gomes, A. S. L. "Picosecond pulse compression and nonlinear processes in single mode optical fibres." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38334.
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Yao, Wang. "4?50G bps PAM4 System over 60km of Single-Mode Fiber." Thesis, University of Louisiana at Lafayette, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10277257.
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<p>In recent years, the growth demand of information transmission has promoted the development of communication technology. Many modulation methods are used in many fields, such as QPSK and OFDM, which are used in long-distance communication. In this thesis, I discussed the PAM-4, which can be used in inter-data center (<80km) links due to its better performance and lower cost. Then I tested one channel 4?50Gbps PAM-4 system and eight channels 4?50Gbps PAM-4 system with varying degrees of gain of optical amplifier and length of DCF. Finally, I discussed the performance of the two designs and figured out the factors that affect the transmission system.
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Salehiomran, Ali. "A universal approach to single longitudinal mode operation in fiber lasers." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123200.
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It is well-known that fiber ring lasers (FRLs) suffer from multiple longitudinal mode (MLM) operation due to their cavity length. Although the average optical output power from an MLM FRL may remain constant, the optical power distribution among the longitudinal modes fluctuates. As a result, the output signal of an MLM FRL is degraded by intensity fluctuations, mode competition, and mode hopping. Therefore, it is desirable to force FRLs to operate in single longitudinal mode (SLM) condition.Various approaches have been reported to achieve SLM operation in FRLs including the use of a saturable absorber, a high finesse fiber Bragg grating Fabry-Perot Etalon, a multi-ring cavity architecture, and simultaneous oscillation of multi wavelengths with similar output powers. Each of the aforementioned SLM forcing mechanisms set restrictions on FRLs and can only be applied to a specific FRL architecture. For instance, if the gain medium, wavelength of operation, or tunability range of an FRL needs to be altered, the architecture and design of the SLM forcing mechanism also needs to be altered.In this thesis, I propose two approaches to achieve SLM operation in FRLs. The first approach applies a novel technique to realize arbitrary optical transfer functions based on the use of delay lines and optical waveguide couplers. Following this technique, the transfer function is expressed as a truncated Fourier series with the tap coefficients that are either purely real or purely imaginary. Therefore, the need for bulky electro-optic phase shiftersis alleviated, the complexity of the integration process is significantly reduced, and the resulting optical integrated circuit does not require any further processing while operated.The second approach uses optical couplers and fibers to form an all-pole-type cavity structure (APTCS) that compensates the propagation delay of the FRL cavity and suppresses the longitudinal modes. This structure is based on the Smith predictor control scheme, which is specifically designed to eliminate the delay term from the denominator of the closed-loop transfer function. The proposed structure is applicable to arbitrary wavelength,gain medium, and FRL architecture. Therefore, the proposed APTCS alleviates the main restrictions set on FRLs by the SLM forcing mechanism, and can be considered as a universal approach to SLM operation in FRLs.<br>En raison de la longueur de leur cavité, les lasers à fibre en anneau (FRLs) sont réputés pour osciller à de multiples modes longitudinaux (MLM). Bien que la puissance optique moyenne issue d'un FRL MLM puisse être constante, la distribution de puissance de ces modes longitudinaux varie. En conséquence, les performances d'un FRL MLM sont dégradées par les fluctuations d'intensité, par un effet de compétition entre modes, et finalement par des sauts de mode. Il est donc désirable de forcer l'opération des FRLs dans un mode longitudinal unique (SLM).Différentes approches permettant une opération SLM ont été présentées. Parmi ces dernières, l'utilisation d'absorbants saturables, un étalon Fabry-Pérot à réseaux de Bragg à haute finesse, une architecture de cavité à multiples anneaux, et l'oscillation simultanée à plusieurs longueurs d'onde avec des puissances de sortie comparables. Chaque mécanisme forçant une oscillation SLM mentionné précédemment impose des restrictions aux FRLs et dépend de leurs architectures respectives. Par exemple, si le milieu de gain, la longueur d'onde d'opération ou leur plage de fonctionnement doivent être changés, l'architecture et le design du mécanisme forçant l'opération SLM doivent également être modifiés.Dans cette thèse, je propose deux approches qui permettent une opération SLM dans des FRLs. La première approche met en application une nouvelle technique permettant de réaliser des fonctions de transfert arbitraires, basée sur l'utilisation de lignes à délai et de coupleurs optiques à guides d'onde. Via cette technique, la fonction de transfert est exprimée par une série de Fourier tronquée dont les coefficients sont purement réels ou purement imaginaires. Grâce à cela, il est possible de se passer de composants électro-optiques à ajustement de phase encombrants, la complexité du procédé d'intégration en est significativement réduite et le circuit optique intégré résultant ne requiert aucun autre ajustement durant son fonctionnement.La seconde approche utilise des coupleurs et fibres optiques pour former une structure de cavité de type tout-pôle (APTCS) qui compense les délais de propagation des cavités FRL et supprime les modes longitudinaux. Cette structure est basée sur le schéma de contrôle qu'est le prédicteur de Smith, spécifiquement conçu pour éliminer le terme de délai du dénominateur de la fonction de transfert en boucle fermée. La structure proposée est applicable indépendamment de la longueur d'onde, du milieu de gain, et de l'architecture du FRL. Ainsi, le APTCS proposé diminue les principales restrictions imposées par les mécanismes forçant l'opération SLM, et peut être considérée comme une approche universelle pour une opération SLM des FRLs.
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Lee, Nancy Yushan. "Performance analysis of single mode optical fiber star networks with reflections." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14035.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1990.<br>Includes bibliographical references (leaves 53-54).<br>by Nancy Yushan Lee.<br>M.S.
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Gatton, Tim. "Using Telemetry Front-end Equipment and Network Attached Storage Connected to Form a Real-time Data Recording and Playback System." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605316.
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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California<br>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.
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LI, ZHENG-LI, and 李政立. "The polarization in single-mode optical fibers." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/11218916274704203445.
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Lin, Ting-chien, and 林廷謙. "Fabrication of Single-mode Cr-doped Fibers." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/32823985279846035160.
Full textAbstract:
碩士<br>國立中山大學<br>光電工程學系研究所<br>98<br>The fabrication of broadband single-mode Cr-doped silica fibers (SMCDSFs) using the fiber drawing-tower method with the modified rod-in-tube technique is demonstrated for the first time.
A preform was assembled by using the grown Cr:YAG rod as core and the silica tube as cladding. The outer and inner diameters of the silica tube are 20 and 7 mm, respectively. The initial dimension of the Cr:YAG crystal rod had a length of 0.03 m and a diameter of 500 μm. The Cr:YAG crystal was grown into a diameter of a 290 μm with a length of 0.12 m by the LHPG method. The SMCDSFs had a 6 μm core and a 125 μm cladding. The transmission loss was 0.08 dB/cm at 1550 nm. The far-field pattern measurements indicated the single-mode characteristic when the propagation wavelength was longer than 1310 nm.
In order to solve the interface of core and cladding, a novel rod-in-tube(RIT) perform was employed by inserting the Cr:YAG crystal rod of 0.03m length and 500 μm diameter into the silica capillary tube, which had the same diameter with the drilled silica rod. The single-mode Cr-doped fibers had successfully been fabricated and the loss had been reduced to 0.03 dB/cm at 1550 nm with a 5 μm core and a 125 μm cladding. Furthermore, the SMCDSFs also had the single-mode characteristic when they operated in the optical communication window.
The successful fabrication of SMCDSFs may be one step forward towards the achievement of utilizing the SMCDSFs as ultra-broadband fiber optical amplifiers to cover the bandwidths in the whole 1300 to 1600 nm range of low-loss and low-dispersion windows of silica fibers and a broadband source for enabling high resolution in optical coherence tomography (OCT).