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IEEE has recently finished its ratification of the IEEE Standard 802.3ba in June 2010 which set the target Ethernet speed as 100 Gbps. The studies on the future trends of the ever-increasing demands for higher speed optical fiber communications show that there is no sign of decline in the demand. Constantly increasing internet traffic and the bandwidth-hungry multimedia services like HDTV, YouTube, voice-over-IP, etc. can be shown as the main driving forces. Indeed, the discussions over the future upgrades on the Ethernet speeds have already been initiated. It is predicted that the next upgrade will enable 400 Gbps Ethernet and the one after will be toward enabling the astounding 1 Tbps Ethernet.Although such high and ultra high transmission speeds are unprecedented over any transmission medium, the bottlenecks for achieving them over the optical fiber remains to be fundamental. At such high operating symbol rates, the signal impairments due to inter- and intra-channel fiber nonlinearities and polarization mode dispersion get exacerbated to the levels that cripple the high-fidelity communication over optical fibers. Therefore, efforts should be exerted to provide solutions that not only answer the need for high-speed transmission but also maintain low operating symbol rates.In this dissertation, we contribute to these efforts by proposing nonbinary-LDPC-coded modulation (NB-LDPC-CM) schemes as enabling technologies that can meet both the aforementioned goals. We show that our proposed NB-LDPC-CM schemes can outperform their prior-art, binary counterparts called bit-interleaved coded modulation (BI-LDPC-CM) schemes while attaining the same aggregate bit rates at a lower complexity and latency. We provide comprehensive analysis on the computational complexity of both schemes to justify our claims with solid evidence. We also compare the performances of both schemes by using amplified spontaneous emission (ASE) noise dominated optical fiber transmission and short to medium haul optical fiber transmission scenarios. Both applications show outstanding performances of NB-LDPC-CM schemes over the prior-art BI-LDPC-CM schemes with increasing gaps in coding gain as the transmission speeds increase. Furthermore, we present how a rate-adaptive NB-LDPC-CM can be employed to fully utilize the resources of a long haul optical transport network throughout its service time.

At the heart of high harmonic generation lies a combination of optical and collision physics entwined by a strong laser field. An electron, initially tunnel-ionized by the field, driven away then back in the continuum, finally recombines back to rest in its initial ground state via a radiative transition. The emitted attosecond (atto=10^-18) XUV light pulse carries all the information (polarization, amplitude and phase) about the photorecombination continuum-to-ground transition dipolar field. Photorecombination is related to the time-reversed photoionization process. In this perspective, high-harmonic spectroscopy extends well-established photoelectron spectroscopy, based on charged particle detection, to a fully coherent one, based on light characterization. The main achievement presented in this thesis is to use high harmonic generation to probe femtosecond (femto=10^-15) chemical dynamics for the first time. Thanks to the coherence imposed by the strong driving laser field, homodyne detection of attosecond pulses from excited molecules undergoing dynamics is achieved, the signal from unexcited molecules acting as the reference local oscillator. First, applying time-resolved high-harmonic spectroscopy to the photodissociation of a diatomic molecule, Br2 to Br + Br, allows us to follow the break of a chemical bond occurring in a few hundreds of femtoseconds. Second, extending it to a triatomic (NO2) lets us observe both the previously unseen (but predicted) early femtosecond conical intersection dynamics followed by the late picosecond statistical photodissociation taking place in the reaction NO2 to NO + O. Another important realization of this thesis is the development of a complementary technique to time-resolved high-harmonic spectroscopy called LAPIN, for Linked Attosecond Phase INterferometry. When combined together, time-resolved high-harmonic spectroscopy and LAPIN give access to the complex photorecombination dipole of aligned excited molecules. These achievements lay the basis for electron recollision tomographic imaging of a chemical reaction with unprecedented angstrom (1 angstrom= 0.1 nanometer) spatial resolution. Other contributions dedicated to the development of attosecond science and the generalization of high-harmonic spectroscopy as a novel, fully coherent molecular spectroscopy will also be presented in this thesis.

Des méthodes de modulation et de détection de la lumière originales ont été étudiées afin d’améliorer la performance des systèmes de transmission optique longue distance. Des formats de modulation multiplexés en polarisation, utilisant plusieurs niveaux de phase ont été étudiés en particulier. La détection cohérente associée à un traitement numérique du signal a également été choisie au niveau de la réception afin d’optimiser la performance du système. Cela permet notamment de compenser de façon très efficace les distorsions linéaires introduites par la propagation dans le fibre optique, telles que la dispersion chromatique et la dispersion modales de polarisation. Après propagation sur grande distance, le rapport signal à bruit devient une limitation importante. L’autre limitation provient des interactions non linéaire entre la lumière et la fibre optique qui limitent la puissance maximale que l’on peut injecter dans la fibre optique.La première transmission multiplexée en longueur d’onde sur grandes distances (>1000km) utilisant la détection cohérente a notamment été démontrée.Afin de minimiser l’impact de ces effets non linéaires, différentes stratégies ont été proposées et investiguées. L’impact du multiplexage de polarisation a notamment été quantifié dans des configuration où la dispersion chromatique de la fibre est compensée régulièrement dans la liaison et dans le cas où elle n’est compensée qu’en fin de liaison de façon numérique.La proposition d’utiliser un format de modulation à 2 niveaux de phase ainsi que les algorithmes permettant de le détecter ont été fait. Le gain de performance obtenu par rapport à la solution conventionnelle à 4 niveaux de phase a été montré.Au débit de 100Gb/s, la démonstration de la première transmission sur des distances transocéanique a également été faite.Ces travaux de recherche ont été notamment utilisés pour définir puis développer des produits Alcatel-Lucent qui sont maintenant commercialisés, à 40Gb/s en utilisant un format de modulation multiplexé en polarisation à deux niveaux de phase, et à 100Gb/s en utilisant un format multiplexé en polarisation à quatre niveaux de phase. / Modulation and detection methods have been studied to improve the performance of optical long distance communication systems. Polarization division multiplexed modulation and multilevel phase modulation format have been evaluated. Coherent detection associated with digital signal processing has been selected at the receiver side to optimize system performance. This receiver design allows especially to compensate linear distortions induced by fiber optics propagation very efficiently. After long distance propagation, optical signal to noise ratio is a major limitation. The other main limitation comes from non linear interactions of light and fiber optics which put a limit on the maximum power to be injected within fiber optics.The first wavelength division multiplexed transmission over long distances (>1000km) using coherent detection has been demonstrated.Various strategies have been proposed to minimize the impact of non linear effect. The impact of polarisation multiplexing has been quantified in configuration where chromatic dispersion is either regularly optically compensated within the line or digitally compensated at the receiver end.The proposition to use a polarization multiplexed format using only 2 phase levels as well as the algorithms capable to detect them has been done. The performance gain obtained compared to the convention solution using 4 phase levels has been demonstrated.At 100Gb/s bit rate, the demonstration of the first transmission over trans-oceanic distance has also been done.These research work have been used to define and then develop Alcatel-Lucent products which are now commercialized, at 40Gb/s by using a polarization multiplexed and 2 phase levels modulation format, and at 100Gb/s by using a polarization multiplexed 4 phase levels format.

Over the past few years there has been an extensive growth in data traffic consumption devices. Billions of mobile data devices are connected to the global wireless network. Customers demand revived services and up-to-date developed applications, like real-time video and games. These applications require reliable and high data rate wireless communication with high throughput network. One way to meet these requirements is by increasing the number of transmit and/or receive antennas of the wireless communication systems. Massive multiple-input multiple-output (MIMO) has emerged as a promising candidate technology for the next generation (5G) wireless communication. Massive MIMO increases the spatial multiplexing gain and the data rate by adding an excessive number of antennas to the base station (BS) terminals of wireless communication systems. However, building efficient algorithms able to decode a coherently or non-coherently large flow of transmitted signal with low complexity is a big challenge in massive MIMO. In this dissertation, we propose novel approaches to achieve optimal performance for joint channel estimation and signal detection for massive MIMO systems. The dissertation consists of three parts depending on the number of users at the receiver side. In the first part, we introduce a probabilistic approach to solve the problem of coherent signal detection using the optimized Markov Chain Monte Carlo (MCMC) technique. Two factors contribute to the speed of finding the optimal solution by the MCMC detector: The probability of encountering the optimal solution when the Markov chain converges to the stationary distribution, and the mixing time of the MCMC detector. First, we compute the optimal value of the “temperature'' parameter such that the MC encounters the optimal solution in a polynomially small probability. Second, we study the mixing time of the underlying Markov chain of the proposed MCMC detector. We assume the channel state information is known in the first part of the dissertation; in the second part we consider non-coherent signal detection. We develop and design an optimal joint channel estimation and signal detection algorithms for massive (single-input multiple-output) SIMO wireless systems. We propose exact non-coherent data detection algorithms in the sense of generalized likelihood ratio test (GLRT). In addition to their optimality, these proposed tree based algorithms perform low expected complexity and for general modulus constellations. More specifically, despite the large number of the unknown channel coefficients for massive SIMO systems, we show that the expected computational complexity of these algorithms is linear in the number of receive antennas (N) and polynomial in channel coherence time (T). We prove that as $N \rightarrow \infty$, the number of tested hypotheses for each coherent block equals $T$ times the cardinality of the modulus constellation. Simulation results show that the optimal non-coherent data detection algorithms achieve significant performance gains (up to 5 dB improvement in energy efficiency) with low computational complexity. In the part three, we consider massive MIMO uplink wireless systems with time-division duplex (TDD) operation. We propose an optimal algorithm in terms of GLRT to solve the problem of joint channel estimation and data detection for massive MIMO systems. We show that the expected complexity of our algorithm grows polynomially in the channel coherence time (T). The proposed algorithm is novel in two terms: First, the transmitted signal can be chosen from any modulus constellation, constant and non-constant. Second, the algorithm decodes the received noisy signal, which is transmitted a from multiple-antenna array, offering exact solution with polynomial complexity in the coherent block interval. Simulation results demonstrate significant performance gains of our approach compared with suboptimal non-coherent detection schemes. To the best of our knowledge, this is the first algorithm which efficiently achieves GLRT-optimal non-coherent detections for massive MIMO systems with general constellations.

La demande en capacité liée à la transmission de tout type d’information (voix, vidéos, données, etc.) ne cesse de croître. Afin de répondre à cette demande croissante, de nouvelles générations de systèmes de communication multiplexés en longueur d’onde transmettant des débits élevés d’information par canal (100 Gbit/s ou plus) doivent être conçues. En plus des fibres ayant de très faibles pertes, des amplificateurs à fibre dopée à l’Erbium et du multiplexage en longueur d’onde, des technologies sont mises en place, comme notamment le multiplexage en polarisation, la détection cohérente, les formats de modulation multi-niveaux et plus récemment le multiplexage spatial. Des interrogations résident sur l’impact du multiplexage en polarisation ainsi qu’un développement vers des formats de modulation plus évolués incluant modulation de phase et multiplexage en polarisation. Dans cette thèse, afin de contribuer à l’augmentation du produit capacité x distance dans les systèmes de transmission Nx100 Gbit/s par fibre optique également multiplexés en polarisation et utilisant la détection cohérente, nous avons étudié d’une part, la mise en forme spectrale des signaux à l’émission pour augmenter la densité spectrale d’information (ISD: Information Spectral density). Dans cette optique, nous avons étudié l’impact du filtrage étroit gaussien du second ordre et de la mise en forme spectrale en racine de cosinus surélevé (RRC: Root Raised Cosine) sur les signaux émis dans le cas de modulations en Polarization Division Multiplexed-Quaternary Phase Shift Keying (PDM-QPSK) et Polarization-Switched-Quaternary Phase Shift Keying (PS-QPSK). Ceci a été réalisé en simulation numérique en considérant un espacement spectral entre les différents canaux variable. Nous avons montré qu’en tenant compte à la fois du facteur de qualité maximal et de la densité spectrale d’information, l’application de la mise en forme RRC sur des signaux modulés en PS-QPSK, fournit de meilleures performances de transmission dans une configuration où toute la dispersion est compensée en fin de propagation, pour toutes les valeurs d’espacement spectral étudiées. D’autre part, nous nous sommes intéressés aux effets non-linéaires qui limitent la portée de ces systèmes en dégradant pendant la propagation, les symboles émis, par les interactions entre des symboles d’un même canal, entre canaux ou modes de polarisation. La compréhension et la réduction de l’impact des effets non-linéaires est indispensable lorsqu’on veut utiliser certaines technologies pour augmenter la densité spectrale d’information. L’utilisation du multiplexage en polarisation par exemple, se heurte aux dégradations causées par les effets non-linéaires car de nouvelles interactions entre symboles sont présentes pendant la propagation. Par conséquent le développement des futurs systèmes ayant des débits plus élevés de 400 Gbit/s et 1 Tbit/s par canal passe par une diminution de l’impact des effets non-linéaires. Nous avons établi dans ce travail de thèse, des règles de conception permettant de réduire l’impact des effets non-linéaires entre polarisation dans les systèmes de transmission optiques considérés / The ever-increasing demand of capacity in very high bit rate coherent optical transmission systems has paved the way towards the investigation of several techniques such as the use of ultra-low loss fibers, Erbium doped fiber amplifiers, polarization and wavelength division multiplexing (WDM), coherent detection, multi-level modulation formats, spatial division multiplexing, etc. However, there are questions concerning polarization division multiplexing and a development towards some advanced modulation formats including phase modulation and polarization division multiplexing. In this thesis, in order to increase the capacity-by-distance product of future optical coherent systems using wavelength and polarization division multiplexing, we first study spectral shaping of the transmitted signals to increase the information spectral density. For this purpose, we have numerically investigated the multi-channel transmission performance of Polarization Switched Quadrature Phase Shift Keying (PSQPSK) and we have compared it to the performance of Polarization-Division-Multiplexed QPSK (PDM-QPSK), using Root Raised Cosine (RRC) spectral shaping, in the context of a flexible channel grid. In addition we have presented the advantage of PS-QPSK against PDM-QPSK as a function of the system parameters, while we have also discussed the benefit of a RRC spectral shaping against a tight filtering at the transmitter side with a 2nd order super-Gaussian-shaped filter. Furthermore, we have focused on nonlinear effects that limit the transmission distance by degrading the transmitted symbols during propagation. Analyzing and reducing the impact of nonlinear effects is essential when using technologies that increase the information spectral density such as polarization division multiplexing which causes new nonlinear effects due to additional interactions between symbols during the propagation through the fiber. Therefore a reduction of the impact of nonlinear effects is necessary for the development of future systems with higher bit rates of 400 Gbit/s and 1 Tbit/s per channel. We have established in this thesis, design rules to reduce the impact of nonlinear effects in the optical WDM transmission systems at 100 Gbit/s per channel that use polarization multiplexing

At the heart of high harmonic generation lies a combination of optical and collision physics entwined by a strong laser field. An electron, initially tunnel-ionized by the field, driven away then back in the continuum, finally recombines back to rest in its initial ground state via a radiative transition. The emitted attosecond (atto=10^-18) XUV light pulse carries all the information (polarization, amplitude and phase) about the photorecombination continuum-to-ground transition dipolar field. Photorecombination is related to the time-reversed photoionization process. In this perspective, high-harmonic spectroscopy extends well-established photoelectron spectroscopy, based on charged particle detection, to a fully coherent one, based on light characterization. The main achievement presented in this thesis is to use high harmonic generation to probe femtosecond (femto=10^-15) chemical dynamics for the first time. Thanks to the coherence imposed by the strong driving laser field, homodyne detection of attosecond pulses from excited molecules undergoing dynamics is achieved, the signal from unexcited molecules acting as the reference local oscillator. First, applying time-resolved high-harmonic spectroscopy to the photodissociation of a diatomic molecule, Br2 to Br + Br, allows us to follow the break of a chemical bond occurring in a few hundreds of femtoseconds. Second, extending it to a triatomic (NO2) lets us observe both the previously unseen (but predicted) early femtosecond conical intersection dynamics followed by the late picosecond statistical photodissociation taking place in the reaction NO2 to NO + O. Another important realization of this thesis is the development of a complementary technique to time-resolved high-harmonic spectroscopy called LAPIN, for Linked Attosecond Phase INterferometry. When combined together, time-resolved high-harmonic spectroscopy and LAPIN give access to the complex photorecombination dipole of aligned excited molecules. These achievements lay the basis for electron recollision tomographic imaging of a chemical reaction with unprecedented angstrom (1 angstrom= 0.1 nanometer) spatial resolution. Other contributions dedicated to the development of attosecond science and the generalization of high-harmonic spectroscopy as a novel, fully coherent molecular spectroscopy will also be presented in this thesis.

At a time where almost 1.75 billion people around the world use the Internet on a regular basis, optical communication over optical fibers that is used in long distance and high demand applications has to be capable of providing higher communication speed and re-liability. In recent years, strong demand is driving the dense wavelength division multip-lexing network upgrade from 10 Gb/s per channel to more spectrally-efficient 40 Gb/s or 100 Gb/s per wavelength channel, and beyond. The 100 Gb/s Ethernet is currently under standardization, and in a couple of years 1 Tb/s Ethernet is going to be standardized as well for different applications, such as the local area networks (LANs) and the wide area networks (WANs). The major concern about such high data rates is the degradation in the signal quality due to linear and non-linear impairments, in particular polarization mode dispersion (PMD) and intrachannel nonlinearities. Moreover, the higher speed transceivers are expensive, so the alternative approaches of achieving the required rates is preferably done using commercially available components operating at lower speeds.In this dissertation, different LDPC-coded modulation techniques are presented to offer a higher spectral efficiency and/or power efficiency, in addition to offering aggregate rates that can go up to 1Tb/s per wavelength. These modulation formats are based on the bit-interleaved coded modulation (BICM) and include: (i) three-dimensional LDPC-coded modulation using hybrid direct and coherent detection, (ii) multidimensional LDPC-coded modulation, (iii) subcarrier-multiplexed four-dimensional LDPC-coded modulation, (iv) hybrid subcarrier/amplitude/phase/polarization LDPC-coded modulation, and (v) iterative polar quantization based LDPC-coded modulation.

Currently deployed optical transmission systems use coherent detection for data rates of 40 Gb/s and 100 Gb/s. Quadrature phase shift keying (QPSK) modulation using four phase levels in combination with polarization division multiplexing (PDM) allows transmitting four bits per symbol. The use of more complex modulation formats, such as 16 level quadrature amplitude modulation (16QAM) allows increasing the data rate. However, this method reduces dramatically the transmission reach. For example, when passing from 100 Gb/s PDM-QPSK to 200 Gb/s PDM-16QAM, the reach is reduced by a factor of five. A new and disruptive approach in order to increase the capacity is mode division multiplexing (MDM), and this approach is investigated in the frame of my thesis. I start my thesis with some generalities on optical transmission systems followed by a presentation of their historical evolution against the background of the increasing capacity demand in the worldwide telecommunication networks. Afterwards I show some ways to continue the capacity growth in optical transmission systems before focusing on MDM. I describe the new key elements, notably the few-mode fiber and the few-mode amplifier, the mode-multiplexer / -demultiplexer and the new receiver system. I finish with a presentation of some experiments using entire MDM systems, which allowed us to be among the first research teams worldwide to realize a successful MDM transmission