221 |
Šumové charakteristiky optického signálu zesíleného optickým vláknovým zesilovačem / Noise characteristics of the optical signal amplified by optical fiber amplifierDašovský, Jakub January 2017 (has links)
This master thesis deals with problematics of information transmission trough optical fiber and spreading of the electromagnetic field at wavelengths of light. There are analyzed characteristics of the optical signal, and described methods of measuring wavelength of the optical signal power and noise level of the useful signal. Another examined parameter is OSNR at the input and on the output of the optical fiber amplifier EFDA.
|
222 |
Vláknové difrakční struktury Point-by-Point / The Point-by-Point fiber diffraction structuresValášek, Martin January 2017 (has links)
The diploma thesis described the basic principles and characters of the long period fiber gratings (LPFGs). Our concern was to describe basic mathematical description of these gratings needed to their modelation and simulation. Consequently some exact models leading to changes in the shape of the spectrum LPFGs were suggested, these methods were the chirping, apodization and changes in the average refractive index navg. In the Matlab environment, programes for counting the important parametres LPFGs were created and meanwhile each model leading to the change in the shape of the spectrum was simulated.
|
223 |
An integrated nanoaperture optical-fiber tweezer for developing single-photon sourcesEhtaiba, Jamal Mehemed 04 May 2020 (has links)
In this thesis, an approach for developing single-photon sources at the 1550nm wavelength will be demonstrated, based on optical trapping of luminescent upconverting nanoparticles. A single-photon source is a source that emits a single photon at a time, and hence it is a source of quantum bits that constitutes the basic building units in quantum computers and quantum communications. The approach exploits the plasmonic properties of gold films and the waveguiding characteristics of single mode optical fibers (SMFs). We start by planar nanofabrication of subwavelength nanoapertures in a thin gold film based on finite difference time domain simulations for a peak transmission at the wavelength in question. Subsequently, using ultraviolet curable epoxy adhesion material, a nanoaperture patterned on a gold film can be transferred to an SMF tip forming a nanoantenna enhanced optical fiber tweezer (NAFT). As a final step in building the optical tweezer, a test of the capability of the integrated optical fiber tweezer to trap 20 nm, and 30nm polystyrene nanospheres, as well as luminescent upconverting nanoparticles (UCNPs), has been experimentally realized with encouraging results. In addition to the optical trapping of the luminescent nanoparticles, the nano aperture antenna can improve light coupling into the low loss optical fiber guiding channel. Also, it could have a positive influence on enhancing the photon emission rate through the Purcell effect. Furthermore, we have combined NAFT with a low insertion loss wave splitter, a wavelength-division multiplexer (WDM), to allow measuring the 1550nm photon-emission statistics on a cooled superconducting nanowire single-photon detector (SNSPD) at ~ 2.4o K. Eventually, nanoantenna enhanced optical fiber tweezers can play an essential role in optical trapping towards developing single-photon sources and the emerging technology of quantum information processing, computation, and cryptography. / Graduate
|
224 |
Textile lumineux pour le traitement de l'eau par photocatalyse / Luminous textile for the treatment of water by photocatalysisIndermuhle, Chloé 09 October 2015 (has links)
L'objectif de ce travail de thèse était de tester le textile lumineux en termes de performances photocatalytiques en milieu aqueux. La durabilité des textiles face à une exposition prolongée à une irradiation UVA a été testée. Les tests ont mis en évidence un problème de vieillissement des tissus enduits de TiO2, induisant l'apparition d'une inhomogénéité de l'émission de lumière sur la surface du textile. Un modèle mathématique a été développé afin d'exprimer et de prévoir ce vieillissement en fonction du temps d'exposition aux UVA. Le dépôt d'une couche protectrice de silice a permis de résoudre ce problème de vieillissement. Parallèlement, les textiles lumineux enduits de TiO2 ont été caractérisés. La localisation de SiO2 et TiO2 par MEBE et analyse EDX a été démontrée comme étant homogène sur la surface des fibres optiques, mise à part pour le dépôt de TiO2 P25 localise en amas. La quantité de photocatalyseur déposé sur les textiles ainsi que l'absorbance des dépôts ont été évaluées. L'étude de l'adhérence des dépôts a démontré la stabilité du TiO2. Enfin, les performances photocatalytiques des différents textiles enduits de photocatalyseur ont été testées sur la dégradation de deux polluants modèles, l'acide formique et le phenol, en réacteur ferme. L'étude de la vitesse de dégradation en fonction de la masse de TiO2 a permis de déterminer la masse optimum (environ 2mg cm-2). Des rendements photoniques de l'ordre de 30 à 55% dans le cas de l'acide formique et de 6 à 8% pour le phenol ont été obtenus. Un réacteur pilote plan, ouvert, a permis de confirmer les résultats obtenus et ouvre la voie à une configuration multicouche, en vue d'une application industrielle / The objective of this thesis was to test luminous textiles in terms of photocatalytic performances in aqueous medium. The durability of textile under long-time UVA irradiation was tested. Results showed the aging of luminous textile coated by TiO2, involving an inhomogeneity of light emission on the overall surface of the textile. A mathematical model was developed to express and predict the aging depending on the time of exposure to UVA. Also, a protective layer of silica allows avoiding the optical fiber aging. In parallel, luminous textiles coated by TiO2 were characterized. The location of SiO2 and TiO2 by ESEM and EDX analysis was shown to be uniform over the surface of optical fibers textiles, except for TiO2 P25 coating, located in clusters. The amount of photocatalyst deposited on the textiles, and the absorbance of the coatings were determined. Moreover, the study of coating adhesion demonstrated excellent adhesion and stability of the photocatalyst layer. Finally, the photocatalytic performances of the different TiO2 coatings were tested for degradation of two model pollutants, formic acid and phenol, in batch reactor. The study of the evolution of the degradation rate with the mass of photocatalyst was used to determine the optimum mass of TiO2 (about 2mg cm-2). Photonic yields ranging from 30 to 55% in the case of formic acid and 6 to 8% in the case of phenol were obtained. A continuous plan pilot reactor confirmed the results and opens the way for a multi-layer configuration, for industrial application
|
225 |
Existence of the guided modes of an optical fiberSolov'ëv, Sergey I. 11 April 2006 (has links)
The present paper is devoted to the investigation of the guided wave problem. This problem is formulated as the eigenvalue problem with a compact self-adjoint operator pencil. Applying the minimax principle for the compact operators in the Hilbert space we obtain a necessary and sufficient condition for the existence of a preassigned number of linearly independent guided modes. As a consequence of this result we also derive simple sufficient conditions, which can be easily applied in practice. We give a statement of the problem in a bounded domain and propose an efficient method for solving the problem.
|
226 |
Mesures réparties par réflectométrie fréquentielle sur fibre optique / OFDR for optical fiber detectorsBoldyreva, Ekaterina 20 October 2016 (has links)
Les travaux de la présente thèse concernent l’étude théorique et la réalisation d’un Capteur réparti à Fibres Optiques fondé sur la réflectométrie fréquentielle et la rétrodiffusion de Rayleigh. La genèse de cette méthode remonte aux années 80 pour les mesures distribuées. Il y a un peu plus d’une dizaine d’années qu’elle a été mise en œuvre secrètement pour les meures réparties (continument sensibles) par la société américaine « Luna Innovations ». Cette approche permettant de réaliser des profils continus le long de la fibre des paramètres environnants (température et déformation principalement) offre une très bonne résolution spatiale ainsi qu’une résolution de mesure fine et présente donc un grand intérêt pour de nombreuses applications, venant ainsi en complément des techniques reposant sur la diffusion Raman ou Brillouin. L'aspect théorique de cette méthode dite OFDR Rayleigh a été analysé. Pour effectuer une mesure profilométrique il est nécessaire de déterminer simultanément deux informations : la distance physique allant de l’entrée de la fibre jusqu'au point où un paramètre physique à mesurer a été appliqué, et le paramètre physique proprement dit. Pour réaliser cette mesure un lien entre l'influence du paramètre d’influence et le changement d'indice du cœur de la fibre sous test doit être exploité. Il s’agit donc des sensibilités de mesure, mais aussi de l’influence de l’environnement sur le chemin optique parcouru, et donc sur la localisation précise des points de mesure. Ces différents aspects ont donc été analysés et rapportés dans le présent mémoire. Pour mettre en œuvre cette technique fréquentielle, et en particulier son traitement de signal, relativement complexe, deux méthodes différentes ont été proposées : la première dite « corrélationnelle » (mise en œuvre par « Luna Innovations » mais très peu documentée) et la méthode « tensorielle » proposée uniquement dans le cadre de la présente étude. Etant fondée sur les mesures répétitives des décalages spectraux induits par le paramètre physique à mesurer le long de la fibre, la méthode corrélationnelle est plus universelle, s’adressant à tous types de paramètres d’influence. Pourtant, elle s’avère moins précise du fait d'une erreur systématique dans le calcul des décalages spectraux. La méthode tensorielle, quant à elle, fournit un résultat plus précis, cependant elle n'est applicable que pour les mesures de déformations, puisque reposant sur l'effet élasto-optique dans le cœur de la fibre. Une procédure de traitement de signal a ensuite été élaborée pour les deux méthodes précitées, la corrélationnelle et la tensorielle. Les performances capacités de l'appareil dont nous disposons, Luna OBR 4600, ont également été montrées, tant en ce qui concerne les mesures de température que de déformations. Un banc expérimental mettant en œuvre cette méthode de mesure OFDR-Rayleigh a également été conçu est mis au point au laboratoire. Un logiciel de traitement des données a de fait été élaboré est réalisé. Ce programme a été testé à l'aide d'une simulation et grâce à l’utilisation des données brutes délivrées par l’appareil Luna OBR 4600. Plusieurs tests du programme de traitement des données brutes de cet instrument ont été réalisés. Les résultats de ces tests peuvent être considérés plutôt comme satisfaisants, étant globalement en bon accord avec les résultats fournis directement par l'instrument commercial OBR 4600. Au-delà, de nombreux exemples d'applications innovantes de la méthode Rayleigh OFDR ont été présentés et illustrés. Parmi ceux-ci, citons, le système de détection de fuites de sodium liquide pour la surveillance de fonctionnement des circuits de refroidissement des réacteurs de génération IV que nous avons élaboré, grâce à cette méthode Rayleigh OFDR, et un prototype industriel d'un tel système proposé. Enfin, l’analyse des points pouvant faire l’objet d’améliorations et/ou de marges de progrès a été menée, et est rapportée en fin de mémoire. / The present PhD thesis have been carried out at the Laboratoire de Mesures Optiques (Optical Measurement Laboratory) based at CEA Saclay Nuclear Research Center, France. It concerns theoretical analysis and experimental realizations of a “distributed Optical Fiber Sensor” based on Optical Frequency Domain Reflectometry using the Rayleigh backscattering phenomena. As the OFS community know, such technology has been developed by the US company Luna Innovations Inc., which keeps carefully secret any details of both the technology involved and the signal processing of such instruments, named OBR (Optical Backscattered Reflectometer). Advantageously, the present Rayleigh-OFDR method provides a very high spatial resolution (in comparison with other methods based on reflectometry, i.e. OTDR, DTS Raman, Brillouin BOTDR and BOTDA…) and so remains extremely sought for many applications, especially for Structural Health Monitoring. In the present PhD thesis the theoretical aspects of the Rayleigh OFDR method has been presented. As a reminder, in order to measure a physical parameter profile along the fiber, it is required to determine two subjects simultaneously: the distance at which the physical parameter is applied (i.e. the sensor address) to the fiber under test, and the amplitude of this parameter (i.e. “the measurement” itself). A relation between the influence of any environment parameter (temperature, strain, etc.) and the fiber core refractive index changes has to be used. These relations have been shown, as far as the hypothesis linked to the theoretical aspects. Two different methods for such measurement have been proposed: first of all the “correlation method” (used by Luna) and second “a tensor-based method”, fully innovative as developed during the present PhD thesis. The correlation method may be considered as more “universal” as based on the measurement of spectral shifts caused by the physical parameter to measure. But, in the same time, we consider it is less accurate, as a systematic error may somehow fail the spectral shift calculation algorithm. The tensor method do not suffer of such systematic error, but it remains only applicable to strain sensing, as based on the elasto-optic effect. Signal processing procedure has been elaborated and tested for both methods, and of course discussed in the manuscript. In the same time, performances of the existing Luna OBR 4600 reflectometer has been tested at Lab. and are reported for both temperature and strain measurements. An optical mock-up for Rayleigh OFDR method has also been developed. A software, dedicated to signal processing has been fully developed either. This program has been tested for simulated sensing signals and for raw data delivered by the Luna OBR 4600 reflectometer. Results of such tests could be considered as satisfactory, even some questions to be solved remains. Finally, some practical examples of Rayleigh OFDR industrial applications have been shown and detailed. Moreover, in such context of real applications on field, an innovative Rayleigh OFDR system devoted to liquid sodium leakage detection around secondary cooling circuitry of generation IV nuclear reactors has been developed and tested on a nuclear installation. An industrial prototype of such measurement system has been elaborated. Finally, way of progress are analyzed and discussed for future R&D activities.
|
227 |
Ethernet Over Plastic Optical Fiber for Use in the Control System Network for Automotive ApplicationsNazaretian, Ryan Nicholas 11 December 2015 (has links)
Plastic optical fiber (POF) for use in automotive applications is not a new concept and has been used in some vehicles for infotainment media distribution within the Media Oriented Systems Transport protocol. However, the use of POF for the control network’s physical layer is a concept that has not been implemented in automotive applications. Many aspects of a vehicle can be improved by implementing POF as the physical backbone for the control network. Currently, the Controller Area Network (CAN) is used as the primary backbone control network protocol for most automobiles as it is inexpensive and reliable. However, CAN is limited to 500 kbps in most vehicles and is easily accessible. Ethernet may provide the improvements of speed and security needed in today’s feature rich and connected vehicles. The feasibility of implementing Ethernet over POF as the control network for automotive applications is the topic of this research investigation.
|
228 |
Slab-Coupled Optical Fiber Sensors for Electric Field Sensing ApplicationsGibson, Richard S. 20 November 2009 (has links) (PDF)
This dissertation presents the creation of slab coupled optical sensors (SCOS) for electric field sensing applications. SCOS devices utilize the benefits of an optical fiber system for high bandwidth and low electromagnetic interference. These sensors are fabricated by means of mode coupling between a small section of D-shaped optical fiber (D-fiber) with a multi-mode electro-optic slab waveguide. Electric field detection is accomplished by monitoring the behavior of the resonances, seen as transmission dips in the D-fiber transmission, as they shift with electric fields. The novelties of SCOS devices include their small compact nature, potential for sensor multiplexing and a dielectric structure allowing low electromagnetic interference. The SCOS developed in this work been used to measure fields as low as 30 V/m with 1 kHz resolution bandwidth and a high degree of linearity. Due to their compact size they are capable of placement within devices to measure interior electric fields immeasurable by other sensors that are either too large for internal placement or disruptive of the internal fields due to metallic structure. Wavelength multiplexing allows multiple sensors to be placed on a single fiber for mapping electric fields at multiple instances. As an extension, SCOS multiplexing allows the potential for 3-d field sensing by use of multiple electro-optic crystals having orthogonal orientations of the electro-optic axis. This work performs a thorough analysis of SCOS design in order to optimize sensor efficiency for its various applications. Furthermore, the straightforward fabrication process for these sensors is outlined for the development of future uses of these sensors.
|
229 |
Mode-division Multiplexed Transmission In Few-mode FibersBai, Neng 01 January 2013 (has links)
As a promising candidate to break the single-mode fiber capacity limit, mode-division multiplexing (MDM) explores the spatial dimension to increase transmission capacity in fiberoptic communication. Two linear impairments, namely loss and multimode interference, present fundamental challenges to implementing MDM. In this dissertation, techniques to resolve these two issues are presented. To de-multiplex signals subject to multimode interference in MDM, Multiple-InputMultiple-Output (MIMO) processing using adaptive frequency-domain equalization (FDE) is proposed and investigated. Both simulations and experiments validate that FDE can reduce the algorithmic complexity significantly in comparison with the conventional time-domain equalization (TDE) while achieving similar performance as TDE. To further improve the performance of FDE, two modifications on traditional FDE algorithm are demonstrated. i) normalized adaptive FDE is applied to increase the convergence speed by 5 times; ii) masterslave carrier recovery is proposed to reduce the algorithmic complexity of phase estimation by number of modes. Although FDE can reduce the computational complexity of the MIMO processing, due to large mode group delay (MGD) of FMF link and block processing, the algorithm still requires enormous memory and high hardware complexity. In order to reduce the required tap length (RTL) of the equalizer, differential mode group delay compensated fiber (DMGDC) has been proposed. In this dissertation, the analytical expression for RTL is derived for DMGDC systems under the weak mode coupling assumption. Instead of depending on the overall MGD of the link iii in DMGD uncompensated (DMGDUC) systems, the RTL of DMGDC systems depend on the MGD of a single DMGDC fiber section. The theoretical and numerical results suggest that by using small compensation step-size, the RTL of DMGDC link can be reduced by 2 orders of magnitude compared to DMGDUC link. To compensate the loss of different modes, multimode EDFAs are presented with reconfigurable multimode pumps. By tuning the mode content of the multimode pump, modedependent gain (MDG) can be controlled and equalized. A proto-type FM-EDFA which could support 2 LP modes was constructed. The experimental results show that by using high order mode pumps, the modal gain difference can be reduced. By applying both multimode EDFA and equalization techniques, 26.4Tb/s MDM-WDM transmission was successfully demonstrated. A brief summary and several possible future research directions conclude this dissertation.
|
230 |
Polymer Optical Fibers For Luminescent Solar ConcentrationBanaei, Esmaeil 01 January 2013 (has links)
Luminescent solar concentrators (LSC’s) are promising candidates for reducing the cost of solar power generation. Conventional LSC’s are slab waveguides coated or doped with luminescence materials for absorption and guiding of light to the slab edges in order to convert optical energy into electricity via attached photovoltaic (PV) cells. Exploiting the advantages of optical fiber production, a fiber LSC (FLSC) is presented in this thesis, in which the waveguide is a polymeric optical fiber. A hybrid fiber structure is proposed for an efficient two-stage concentration of incident light, first into a small doped core using a cylindrical micro-lens that extends along the fiber, and second to the fiber ends by guiding the fluoresced light from the active dopants. Flexible sheets are assembled with fibers that can be bundled and attached to small-area PV cells. Small dimensions and directional guiding of the fibers allow for approximately one order of magnitude geometrical gain improvement over that of existing flat LSC’s. In addition, the undesired limit of LSC size is eliminated in one direction. Modeling and optimization of an FLSC design is presented using polarization-ray tracing under realistic conditions with solar spectrum radiation and broad-band absorption and emission spectra of fluorescence materials with their inevitable self-absorption effect. Methods and results of fabrication and accurate optical characterization of such FLSC using two off-the-shelf organic dyes and a commercially available polymer, COP, are discussed in detail. Fiber preforms, fabricated under optimized conditions for lowlight transport loss, are thermally iv drawn into sub-millimeter-size fibers. Characterization of several samples with various concentrations of the two dyes shows an optical-to-optical conversion efficiency of 9.1% for a tandem combination of two 2.5-cm-long fibers with the efficiency gradually decreasing to 4.9% with increase in fiber length to 10 cm.
|
Page generated in 0.056 seconds