<p>Ultrafast laser-based diagnostic techniques are powerful tools for the detailed understanding of highly dynamic combustion chemistry and physics. The ultrashort pulses provide unprecedented temporal resolution along with high peak power for broad spectral range−ideal for nonlinear signal generation at high repetition rate−with applications including next-generation combustors for gas turbines, plasma-assisted combustion, hypersonic flows and rotating detonation engines. The current work focuses on advancing (i) femtosecond (fs) two-photon laser-induced fluorescence, and (ii) hybrid femtosecond/picosecond vibrational and rotational coherent anti-Stokes Raman scattering (fs/ps RCARS and VCARS) to higher pressures for the first time. </p><p>Quantitative single-laser-shot kHz-rate concentration measurements of key atomic (O-atom) and molecular (CO) species is presented using femtosecond two-photon laser-induced fluorescence (TP-LIF) for a range of equivalence ratios and pressures in diffusion flames. A multitude of signal-interfering sources and loss mechanisms−relevant to high-pressure fs TP-LIF applications−are also quantified up to 20 atm to ensure high accuracy. The pressure scaling of interferences take into account degradation, attenuation and wave-front distortion of the excitation laser pulse; collisional quenching and pressure dependent transition line-broadening and shifting; photolytic interferences; multi-photon ionization; stimulated emission; and radiation trapping. </p><p>Hybrid fs/ps VCARS of N₂ is reported for interference-free temperature measurement at 1300-2300 K in high-pressure, laminar diffusion flames up to 10 atm. A time asymmetric probe pulse allowed for detection of spectrally resolved CARS signals at probe delays as early as ~200-300 fs while being independent of collisions for the full range of pressures and temperatures. Limits of collisional independence, accuracy and precision of the measurement is explored at various probe-pulse delays, pressures and temperatures. </p><p> </p><p>Additionally, a novel all diode-pumped Nd:YAG amplifier design is presented for generation of time-synchronized ps-probe pulses for hybrid fs/ps RCARS of N₂. High-energy, nearly transform-limited, single-mode, chirp-free ps probe-pulses are generated at variable pulsewidths. The detailed architecture and characterization of the laser is presented. kHz-rate RCARS thermometry is presented up to 2400 K. Excellent spatial, spectral, and temporal beam quality allowed for fitting the theoretical spectra with a simple Gaussian model for the probe pulse with temperature accuracies of 1-2%. </p> <p><br></p>

Initialement poussées par le marché résidentiel, les évolutions du réseau d’accès optique sont aujourd’hui également stimulées par l’expansion du réseau mobile. Comme le montre le premier chapitre de ce document, l’introduction d’un multiplexage en longueur d’onde dense constitue l’une des solutions privilégiées pour permettre la montée en débit dans les réseaux d’accès optique. Dans cette thèse, l’impact de l’introduction du multiplexage en longueur d’onde dense est étudié sous trois axes :• Une prochaine étape de l’évolution des technologies pour les réseaux d’accès passerait par une hybridation entre d’une part, un multiplexage temporel (hérité des précédentes générations), et d’autre part, un multiplexage en longueur d’onde dense. Cette technologie, appelée NGPON2-TWDM, permet aujourd’hui d’envisager des débits de 40Gb/s à 80Gb/s grâce à 4 ou 8 canaux. Les difficultés liées à la stabilité de la longueur d’onde lors de l’émission de données en mode paquet dans le sens montant du lien, ainsi que les solutions associées, sont étudiées dans le second chapitre.• L’importance du marché que représente le réseau d’accès optique (aussi bien pour les clients résidentiels que pour les réseaux mobiles), induit la nécessité pour les différentes générations de technologies de coexister au sein d’une même infrastructure. Du fait des fortes puissances optiques en jeu et des plages spectrales allouées à chaque technologie, cette coexistence peut induire des interactions entre technologies par émission Raman stimulée, dont le principe et les impacts sont décrits dans le troisième chapitre.• Enfin, la quatrième partie de ce document est dédiée à l’étude des limites et potentialités de la technologie self-seeded pour le multiplexage en longueur d’onde dense en bande O, capable de stabiliser automatiquement et passivement la longueur d’onde d’émission de chacun des émetteurs du système. / Initially led by the residential market, today’s optical access network evolutions are stimulated by mobile network expansion. As shown in the first chapter of this document, dense wavelength division multiplexing is one of the favorite solutions in order to increase optical access networks throughput. In this thesis, we propose a study of dense wavelength division multiplexing introduction according to three main topics :• Service providers and equipment suppliers have decided that the next step in residential market evolution will consist in a hybridization between, on one hand, a legacy time division multiplexing, and on the other hand, a dense wavelength division multiplexing. Named NG-PON2, this technology allows today 40Gb/s to 80Gb/s thanks to 4 to 8 channel pairs. Wavelength stability of the upstream emitter under burst mode operation, and related solutions, are studied in the second chapter.• Market importance (for both residential market and mobile networks) requires the different technologies generations to coexist on the same infrastructure. Due to the high optical power and the wavelength spans allocated to each technology, this coexistence can lead to technologies interactions by stimulated Raman scattering, as described in the third chapter.• Finally, the fourth part of this document describes the limits and potentialities of the self-seeded emitter technology for O-band dense wavelength division multiplexing, able to automatically and passively self-stabilize the wavelength of each emitter.

[pt] Neste trabalho é apresentado um estudo sobre a determinação matemática dos valores da dispersão cromática total, do zero de dispersão distribuído e efeitos não lineares em fibras ópticas de dispersão deslocada (DS). Uma metodologia para caracterização das dispersões cromáticas e para os zeros de dispersão local das fibras estudadas é elaborada com a utilização do modelo de fibra degrau equivalente e de aproximações entre as fibras ópticas dos enlaces trabalhados. A relação entre o diâmetro do campo modal e o zero de dispersão cromática distribuído segundo A. Rossaro [6] é discutida e comprovada através da realização de uma série de medidas práticas para a determinação dos efeitos não lineares das fibras de dispersão deslocada dos enlaces da Petrobrás. O objetivo deste trabalho é analisar estes efeitos prejudiciais a transmissão de sinais ópticos de alta velocidade apresentados nos cabos submarinos da Petrobrás entre o Porto de Imbetiba e as plataformas de Pargo I e Pampo I na Bacia de Campos, analisando os resultados obtidos e caracterizando as possibilidades de upgrade destes enlaces. / [en] This work presents a study on the mathematical determination of the total chromatic dispersion, zero dispersion wavelength and nonlinear optical effects in dispersion shifted (DS) fiber optic system. A methodology to determine the chromatic dispersion and zero dispersion wavelength is proposed using the equivalent step index model and the similarity of the total chromatic dispersion measured in fibers of the links under study. The relationship between the mode field diameter and the zero dispersion wavelength according to A. Rossaro [6] is discussed and proven with a series of practical measurements for the determination of the nonlinear effects of the dispersion shifted optical fibers of Petrobras links Imbetiba - Pargo and Imbetiba - Pampo of the Campos Basin. / [es] En este trabajo se presenta un estudio sobre la determinación matemática de los valores de dispersión cromática total, del cero de dispersión distribuido y los efectos no lineales en fibras ópticas de dispersión desplazada (DS). Se elabora una metodología para la caracterización de las dispersiones cromáticas y para los ceros de dispersión local de las fibras estudiadas; utililizando el modelo de fibra escalón equivalente y de aproximaciones entre las fibras ópticas de los enlace. Se discute la relación entre el diámetro del campo modal y el cero de dispersión cromática distribuido según A. Rosaro [6] se comprueba a través de la realización de una serie de medidas prácticas para la determinación de los efectos no lineales de las fibras de dispersión desplazada de los enlaces de la Petrobrás. EL objetivo de este trabajo es analizar los efectos perjudiciales a la transmisión de señales ópticos de alta velocidad que se presentan en los cables submarinos de la Petrobrás entre el Puerto de Imbetiba y las plataformas de Pargo I y Pampo I en la Bacia de Campos, analizando los resultados obtenidos y caracterizando las posibilidades de upgrade de estos enlaces.