All Optical Signal Processing Technologies in Optical Fiber Communication

Due to continued growth of internet at starling rate and the introduction of new broadband services, such as cloud computing, IPTV and high-definition media streaming, there is a requirement for flexible bandwidth infrastructure that supports mobility of data at peta-scale. Elastic networking based on gridless spectrum technology is evolving as a favorable solution for the flexible optical networking supportive next generation traffic requirements. Recently, research is centered on a more elastic spectrum provision methodology than the traditional ITU-T grid. The main issue is the requirement for a transmission connect, capable of accommodating and handling a variety of signals with distinct modulation format, baud rate and spectral occupancy. Segmented use of the spectrum could lead to the shortage of availableness of sufficiently extensive spectrum spaces for high bitrate channels, resulting in wavelength contention. On-demand space assignment creates not only deviation from the ideal course but also have spectrum fragmentation, which reduces spectrum resource utilization. This chapter reviewed the recent research development of feasible solutions for the efficient transport of heterogeneous traffic by enhancing the flexibility of the optical layer for performing allocation of network resources as well as implementation of optical node by all optical signal processing in optical fiber communication

Physical Layer Aware Optical Networks

This thesis describes novel contributions in the field of physical layer aware optical networks. IP traffic increase and revenue compression in the Telecom industry is putting a lot of pressure on the optical community to develop novel solutions that must both increase total capacity while being cost effective. This requirement is pushing operators towards network disaggregation, where optical network infrastructure is built by mix and match different physical layer technologies from different vendors. In such a novel context, every equipment and transmission technique at the physical layer impacts the overall network behavior. Hence, methods giving quantitative evaluations of individual merit of physical layer equipment at network level are a firm request during network design phases as well as during network lifetime. Therefore, physical layer awareness in network design and operation is fundamental to fairly assess the potentialities, and exploit the capabilities of different technologies. From this perspective, propagation impairments modeling is essential. In this work propagation impairments in transparent optical networks are summarized, with a special focus on nonlinear effects. The Gaussian Noise model is reviewed, then extended for wideband scenarios. To do so, the impact of polarization mode dispersion on nonlinear interference (NLI) generation is assessed for the first time through simulation, showing its negligible impact on NLI generation. Thanks to this result, the Gaussian Noise model is generalized to assess the impact of space and frequency amplitude variations along the fiber, mainly due to stimulated Raman scattering, on NLI generation. The proposed Generalized GN (GGN) model is experimentally validated on a setup with commercial linecards, compared with other modeling options, and an example of application is shown. Then, network-level power optimization strategies are discussed, and the Locally Optimization Global Optimization (LOGO) approach reviewed. After that, a novel framework of analysis for optical networks that leverages detailed propagation impairment modeling called the Statistical Network Assessment Process (SNAP) is presented. SNAP is motivated by the need of having a general framework to assess the impact of different physical layer technologies on network performance, without relying on rigid optimization approaches, that are not well-suited for technology comparison. Several examples of applications of SNAP are given, including comparisons of transceivers, amplifiers and node technologies. SNAP is also used to highlight topological bottlenecks in progressively loaded network scenarios and to derive possible solutions for them. The final work presented in this thesis is related to the implementation of a vendor agnostic quality of transmission estimator for multi-vendor optical networks developed in the context of the Physical Simulation Environment group of the Telecom Infra Project. The implementation of a module based on the GN model is briefly described, then results of a multi-vendor experimental validation performed in collaboration with Microsoft are shown

Software Defined Applications in Cellular and Optical Networks

abstract: Small wireless cells have the potential to overcome bottlenecks in wireless access through the sharing of spectrum resources. A novel access backhaul network architecture based on a Smart Gateway (Sm-GW) between the small cell base stations, e.g., LTE eNBs, and the conventional backhaul gateways, e.g., LTE Servicing/Packet Gateways (S/P-GWs) has been introduced to address the bottleneck. The Sm-GW flexibly schedules uplink transmissions for the eNBs. Based on software defined networking (SDN) a management mechanism that allows multiple operator to flexibly inter-operate via multiple Sm-GWs with a multitude of small cells has been proposed. This dissertation also comprehensively survey the studies that examine the SDN paradigm in optical networks. Along with the PHY functional split improvements, the performance of Distributed Converged Cable Access Platform (DCCAP) in the cable architectures especially for the Remote-PHY and Remote-MACPHY nodes has been evaluated. In the PHY functional split, in addition to the re-use of infrastructure with a common FFT module for multiple technologies, a novel cross functional split interaction to cache the repetitive QAM symbols across time at the remote node to reduce the transmission rate requirement of the fronthaul link has been proposed.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

mixed modulation format for future optical transmission systems

Developing a flexible network to fully utilize the existing spectral resource is a hot topic in the novel paradigm of optical transmission systems. In this thesis, I analysed hybrid modulation formats as an effective technique for the implementation of flexible transponders that are capable of trading-off the delivered data rate by the light path quality of transmission with a finer granularity. The flexible transponder is an enabling technology to introduce the elastic paradigm in the state-of-the-art networks, while maintaining compatibility with the installed equipment, including fibers, mux-demux and ROADMs, as required by telecommunication operators willing to exploit fixed grid WDM transmission. Time division hybrid modulation format (TDHMF) is presented as the first solution. Through combining two modulation formats in the time division, TDHMF can achieve arbitrary bit-per-symbol, and provide a huge amount of flexibilities to the network. A comprehensive theoretical assessment of the back-to-back performances is also introduced. In particular, four different transmitter operation strategies are proposed and evaluated. They are the constant power strategy, the same Euclidean distance strategy, the same BER strategy and the minimum BER strategy. Through the back-to-back performance comparison, the same BER strategy is chosen as the most promising strategy, mainly due to its comparable sensitivity performance and the potential of transponder simplification. This thesis also prepared another solution, which is Flexible M-PAM modulation format (FlexPAM). It is a hybrid of different M-PAMs in all four quadrature of the optical field. Although it providing less flexibility compared to TDHMF, FlexPAM has its unique advantage in two main aspect. Firstly, the inherently time consistent frame structure feature of FlexPAM may require an identical and simple transponder, which is very crucial from the operators point of view. Secondly, from the network perspective, the operators can assign each quadrature of FlexPAM to a specific network tributary and select an M-PAM according to the actual network conditions. Similar to TDHMF, both general characterization and theoretical formulation are discussed in detail. Then, the back-to-back performance of FlexPAM, including the comparison of different transmitter strategies that similar to the one of TDHMF, has been fully studied. The same BER strategy again provided a negligible SNR penalty in contrast to the optimal strategy. At the same time, by using the same FEC code for both M-PAM, the same BER strategy may require a simpler signal processing procedure and reduce the complexity. A subsequent work after the back-to-back analysis is the signal non-linear propagation evaluation of these two novel modulation formats. This thesis provide an extensive simulation analysis on the propagation of a Nyquist-WDM channel comb over an uncompensated and amplified fiber link. Due to the power unbalance in the time division (TDHMF) or in the polarization/quadrature (FlexPAM), the mixed modulation formats normally have some penalty against to the GN-model predictions. To improve their propagation performance, a simple polarization interleaving countermeasure is presented. It works well on TDHMF and has a significant impact on certain case of FlexPAM. Furthermore, the power ratio tuning is also proposed as an easy implemented and effective tool to improve the propagation performance. In the end, the propagation performance of both TDHMF and FlexPAM are compared in terms of the maximum reach versus system net bit rate, in addition, both with and without countermeasures conditions were considered. The results of this investigation showed that TDHMF has almost the same performance as the GN model predictions after the countermeasures employed. FlexPAM can provide a comparable propagation performance in contrast to the GN model predictions. Considering the advantages that mentioned before, the propagation performance of FlexPAM is acceptable