Performance limits in optical communications due to fiber nonlinearity

In this paper, we review the historical evolution of predictions of the performance of optical communication systems. We will describe how such predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems

Transmission optique longue distance avec le format MB-OFDM cohérent à 100 Gbps

Today the 100 Gbps coherent dual polarization quadrature phase shift keying (Co-DP-QPSK) is standardized as the industrial solution for long-haul WDM transmission. Another alternative format to DP-QPSK that permits also to reach a data rate of 100 Gbps and beyond is the coherent orthogonal frequency division multiplexing (OFDM) format. However a doubt exists over the ability of OFDM to be as efficient as QPSK for long-haul WDM transmission due to its supposed higher sensitivity to nonlinear effects . In this thesis, we have investigated the potential of Co-DP-OFDM for 100 Gbps WDM transport. The digital signal processing algorithms are detailed as well as the various experimental set-ups required to carry out and validate the 100 Gbps transceiver. We also present the transmission results obtained with several configurations. In one of these configurations, the 100 Gbps Co-DP-OFDM channel is multiplexed with forty 100 Gbps DP-QPSK channels and all these channels are transmitted over 1000 km of DCF-free G.652 fiber, while in another configuration, the Co-DP-OFDM and Co-DP-QPSK channels are combined with seventy eight 10 Gbps NRZ-OOK channels and transmitted over 1000 km of dispersion managed G.652 fiber line. We have demonstrated that OFDM and QPSK have nearly the same performance after a transmission over 1000 km, and also we have demonstrated that the transmission of these two formats over legacy fiber infrastructure is possible under the condition of decreasing by 5 dB the 10 Gbps NRZ-OOK channel power with respect to the 100 Gbps channels. The results presented in this thesis are very valuable when considering the next generation of 400 Gbps or 1 Tbps for WDM systems.Aujourd'hui, le format « Quadrature Phase Shift Keying » avec multiplexage de polarisation (DP-QPSK) opérant à 100 Gbps est devenue un standard pour la transmission WDM longue distance. Une alternative au format DP-QPSK permettant d’atteindre des débits de 100 Gbps et plus (400 G & 1Tbps) est l’ « Orthogonal Frequency Division Multiplexing » (OFDM). Mais, des interrogations subsistent quant à sa robustesse aux effets non linéaires. Dans cette thèse nous avons étudié le potentiel de la technologie OFDM pour la transmission WDM longue distance à 100 Gbps. Le traitement du signal est détaillé ainsi que la mise en œuvre du transmetteur et récepteur OFDM cohérent. Nous présentons aussi les résultats expérimentaux de la transmission obtenus dans plusieurs configurations. Dans l’une de ces configurations, le canal modulé avec le format DP-OFDM coherent (Co-DP-OFDM) est multiplexé avec 40 canaux modulés en DP-QPSK à 100 Gbps. Les canaux ont ensuite été transmis sur 1000 km de fibre G.652 sans gestion de dispersion chromatique. Dans une autre configuration, les canaux Co-DP-OFDM et Co-DP-QPSK sont combinés avec 78 canaux 10 Gbps NRZ-OOK et transmis sur 1000 km de fibre G.652 avec gestion de dispersion. Nous avons montré que le Co-DP-OFDM et Co-DP-QPSK ont des performances similaires après une transmission de 1000 km sur une ligne sans gestion de dispersion, et nous avons aussi montré que la transmission de ces formats sur une infrastructure de fibre deployée est possible à condition de réduire de 5 dB la puissance des canaux 10 Gbps NRZ-OOK par rapport aux canaux à100 Gbps. Ces résultats sont précieux pour la prochaine génération de systèmes WDM à 400 Gbps ou 1 Tbps

Maximising Achievable Rates of Experimental Nonlinear Optical Fibre Transmission Systems

It is generally expected that the demand for digital data services will continue to grow, placing ever greater requirements on optical fibre networks which carry the bulk of digital data. Research to maximise achievable information rates (AIR) over fibre has led to increasing spectral efficiency, symbol rate and bandwidth use. All of these contribute to transmission impairments due to the nonlinear nature of the optical fibre. This thesis describes research performed to investigate the effects of nonlinear impair- ments on the AIRs of experimental optical fibre transmission. To maximise throughput, the entire available optical bandwidth should be filled with transmission channels. An investigation into large bandwidth transmission through the use of spectrally shaped amplified spontaneous emission noise (SS-ASE) was con- ducted. The enhanced Gaussian noise model is used to analytically describe this tech- nique, and SS-ASE was experimentally shown to provide a lower bound on the AIR. Nonlinear interference (NLI) was modelled from an inter-symbol interference (ISI) model to characterise the noise and was experimentally verified. This new understand- ing helps quantify potential gain available from nonlinearity mitigation. Multicore fibres offer an alternative route to improve AIR, and are susceptible to another noise source known as crosstalk. This inter-core crosstalk can be controlled by suitable design of the fibre, hence in the limiting case, NLI rather than crosstalk will limit AIR. Nonlinearity compensation was, for the first time, experimentally demon- strated in the presence of crosstalk in a homogeneous 7-core fibre and shown to provide an increase in AIR. The results of this thesis can be used to evaluate future transmission systems for maximising information rates. It was shown that experimentally, SS-ASE is a viable transmission tool to evaluate system performance, NLI can be characterised using an ISI model and nonlinearity mitigation is possible in MCF systems limited by crosstalk

The economics of federalism

An important development in public finance theory during recent years has been the emergence of the basic elements of a theory of fiscal federalism, based partly on the theory of public goods, partly on the theory of political process and partly on various aspects of location theory. The aim of the theory is to supply answers to basic and wide-ranging questions relating to the case for and the allocation of functions within a federal system, efficiency aspects of migration between jurisdictions, the case for different kinds of intergovernmental grants arrangements and the forms of debt and taxation arrangements appropriate to a federal structure. This volume gathers together most of the significant contributions to the theory, many of which are somewhat inaccessible. Although primarily concerned with federal constitutions, the book is relevant to the analysis of public policy under unitary constitutions which devolve decision-making autonomy to local or regional governments. It also reviews the current state of the art and thereby points out certain gaps that remain to be filled in the future

Optical differential phase-shift keyed signal generation, transmission and detection

Optical label switching -- Optical performance monitoring -- Multibit delay DPSK demodulation -- OpticalError correction -- FSR optimization -- Free spectral range and optical filtering optimization -- Simulation parameters -- Optical packets -- Performance monitoring -- Multibit delay DQPSK demodulation -- Optical error correction -- Free spectral range and optical filtering optimization