Design And Analysis Of Architectures And Algorithms For Fixed And Flexible Grid Optical Wdm Networks

In general, this dissertation proposes several architectures and algorithms for fixed and flexible grid WDM networks that address near and far term network challenges.

Optical spectrum is becoming scarce with traffic demand growing at 40% per year. Today, the optical spectrum of a fiber is divided using wavelength-division multiplexing (WDM) into optical channels of 50 GHz or 100 GHz. This fixed grid will not be able to efficiently support higher bit-rate transponders (namely, at 400 Gbps and 1 Tbps). Moreover, innovative elastic transponders capable of tuning their data rates by choosing appropriate modulation formats or spectrum width are also being investigated. To exploit the capabilities of elastic transponders and to fit transponders at beyond-100 Gbps rates, the conventional fixed grid has to evolve towards a flexible grid, where an arbitrary number of finer frequency slots (e.g., at 12.5 GHz) can be assigned to serve the client demands. At the same time of the disruptive development of the optical layer, two trends in the general networking/IT fields are prominent: 1. Vertical convergence: convergence of multiple layers of the network stack, e.g., packet and circuit (optical) convergence; 2. Horizontal convergence: convergence of computing, storage, and networking resources, e.g., cloud networking, and information-centric networking (ICN). Hence, we are motivated to study how to adapt the architecture, operation, and services of flexible-grid elastic optical networks to the two prominent trends. For vertical packet/optical convergence, we study dynamic traffic grooming in elastic optical networks. We propose to jointly solve the electrical-layer routing and optical-layer routing and spectrum assignment (RSA). Also, we propose a spectrum reservation scheme that can efficiently utilize the bandwidth variability of lightpaths, reducing operational expenditure (OPEX) as well as increasing spectrum efficiency. We also propose a provisioning policy exploring grooming opportunities both in time and frequency domains in order to achieve high energy efficiency. We review the evolution of traffic-grooming paradigm. Sliceable optical layer based on sliceable transponders and bandwidth-variable reconfigurable optical add/drop multiplexer (BV-ROADM) is identified as a novel technology that could impact the future grooming paradigm by offloading considerable amount of traffic and part of electronic grooming function to the optical layer. We propose two novel network architectures based on sliceable optical layer and their optimal designs. It is found that packet over sliceable (PoS) network architecture consumes the fewest transponders and at the same time achieves either the "lowest-possible" latency or least spectrum usage. We also propose a new dense-wavelength-division multiplexing (DWDM)-centric converged metro/aggregation network, which reduces the usage of electronic packet processing, hence significantly reducing the corresponding OPEX. Both Integer Linear Program (ILP) and heuristics are proposed to address the complex network design problems involving two layers of routing (fiber routing and wavelength routing), wavelength assignment, and survivable design. For horizontal convergence, we investigate how to jointly allocate computing, storage, and networking resources for virtual infrastructures in the problems of network virtualization over both WDM and flexible-grid optical networks. We formulate the problems as mixed integer linear programs (MILP) and propose two heuristics, namely MaxMapping and MinMapping. Numerical examples show that MinMapping performs very close to the optimal results derived by the MILP in both kinds of optical networks, by exploring traffic grooming. Also, it is verified that flexible-grid optical networks can be more spectrum efficient than WDM networks as the substrate for network virtualization. Also, for large service providers (SP) who own their computing, storage, and networking resources, we propose to orchestrate their cache and networking resources in a coordinated way to solve their traffic-engineering (TE) and cache-orchestration (CO) problems in an ICN-enabled networking infrastructure using service popularity. We propose to deal with the joint problems at the service level, in which no specific information about individual contents of services is needed. Numerical results show that our proposed TE and CO schemes can significantly reduce network cost and increase cache hit ratio, with the constraints of satisfying service-level agreements (SLA).

Lo, soul! seest thou not God's purpose from the first? The earth to be spann'd, connected by net-work From Passage to India! Walt Whitman, "Leaves of Grass", 1900. The Internet is growing at a tremendous rate today. New services, such as telephony and multimedia, are being added to the pure data-delivery framework of yesterday. Such high demands on capacity could lead to a "bandwidth-crunch" at the core wide-area network resulting in degra dation of service quality. Fortunately, technological innovations have emerged which can provide relief to the end-user to overcome the In ternet's well-known delay and bandwidth limitations. At the physical layer, a major overhaul of existing networks has been envisaged from electronic media (such as twisted-pair and cable) to optical fibers - in the wide area, in the metropolitan area, and even in the local area set tings. In order to exploit the immense bandwidth potential of the optical fiber, interesting multiplexing techniques have been developed over the years. Wavelength division multiplexing (WDM) is such a promising tech nique in which multiple channels are operated along a single fiber si multaneously, each on a different wavelength. These channels can be independently modulated to accommodate dissimilar bit rates and data formats, if so desired. Thus, WDM carves up the huge bandwidth of an optical fiber into channels whose bandwidths (1-10 Gbps) are compati ble with peak electronic processing speed.

This work addresses the topic of optical networks cross-layer design with a focus on physical-layer-impairment-aware design. Contributors captures both the physical-layer-aware network design as well as the latest advances in service-layer-aware network design. Treatment of topics such as, optical transmissions which are prone to signal impairments, dense packing of wavelengths, dispersion, crosstalk, etc., as well as how to design the network to mitigate such impairments, are all covered.

Research and development on optical wavelength-division multiplexing (WDM) networks have matured considerably. While optics and electronics should be used appropriately for transmission and switching hardware, note that "intelligence'' in any network comes from "software,'' for network control, management, signaling, traffic engineering, network planning, etc.The role of software in creating powerful network architectures for optical WDM networks is emphasized. Optical WDM Networks is a textbook for graduate level courses. Its focus is on the networking aspects of optical networking, but it also includes coverage of physical layers in optical networks. The author introduces WDM and its enabling technologies and discusses WDM local, access, metro, and long-haul network architectures. Each chapter is self-contained, has problems at the end of each chapter, and the material is organized for self study as well as classroom use. The material is the most recent and timely in capturing the state-of-the-art in the fast-moving field of optical WDM networking.

This helpful guide provides practicing engineers, students, and researchers with a systematic, up-to-date introduction to the fundamental concepts, challenges, and state-of-the-art developments in WDM optical networks. The authors rely extensively on real-world examples and draw on the latest research to cover optical network design and provisioning in far greater depth than any other book.

By the end of the decade, approximately 50 billion devices will be connected over the internet using multiple services such as online gaming, ultra-high definition videos, and 5G mobile services. The associated data traffic demand in both fixed and mobile networks is increasing dramatically, causing network operators to have to migrate the existing optical networks towards next-generation solutions. The main challenge within this development stems from network operators having difficulties finding cost-effective next-generation optical network solutions that can match future high capacity demand in terms of data, reach, and the number of subscribers to support multiple network services on a common network infrastructure. Design, Implementation, and Analysis of Next Generation Optical Networks: Emerging Research and Opportunities is an essential reference source that discusses the next generation of high capacity passive optical access networks (PON) in terms of design, implementation, and analysis and offers a complete reference of technology solutions for next-generation optical networks. Featuring research on topics such as artificial intelligence, electromagnetic interface, and wireless communication, this book is ideally designed for researchers, engineers, scientists, and students interested in understanding, designing, and analyzing the next generation of optical networks.

Optical networks based on wavelength-division multiplexing (WDM) tech nology offer the promise to satisfy the bandwidth requirements of the Inter net infrastructure, and provide a scalable solution to support the bandwidth needs of future applications in the local and wide areas. In a waveleng- routed network, an optical channel, referred to as a lightpath, is set up between two network nodes for communication. Using WDM technology, an optical fiber link can support multiple non-overlapping wavelength channels, each of which can be operated at the data rate of 10 Gbps or 40 Gbps today. On the other hand, only a fraction of customers are expected to have a need for such a high bandwidth. Due to the large cost of the optical backbone infrastruc ture and enormous WDM channel capacity, connection requests with diverse low-speed bandwidth requirements need to be efficiently groomed onto hi- capacity wavelength channels. This book investigates the optimized design, provisioning, and performance analysis of traffic-groomable WDM networks, and proposes and evaluates new WDM network architectures. Organization of the Book Significant amount of research effort has been devoted to traffic grooming in SONET/WDM ring networks since the current telecom networks are mainly deployed in the form of ring topologies or interconnected rings. As the long-haul backbone networks are evolving to irregular mesh topologies, traffic grooming in optical WDM mesh networks becomes an extremely important and practical research topic for both industry and academia.

The ever demanding bandwidth requirements for supporting emerging telecom services such as ultra-high-definition video streaming, cloud computing, connected car, virtual/augmented reality, etc., bring to the fore the necessity to upgrade continuously the technology behind transport networks in order to keep pace with this exponential traffic growth. Thus, everything seems to indicate that fixed-grid Wavelength-Division Multiplexed (WDM) networks will be upgraded by adopting a flexible-grid, thus providing finer bandwidth allocation granularities, and therefore, increasing the Grade-of-Service by packing more information in the same spectral band of standard Single-Mode Fibers (SMFs). Nevertheless, unfortunately, the fundamental Shannon's limit of SMFs is rapidly approaching, and, then, the research efforts to increase the SMFs' capacity will be useless. One solution to overcome this capacity crunch effect is to enable one extra dimension in addition to the frequency one, namely, the spatial dimension, thus deploying S parallel paths in order to multiply, in the best case, by S the capacity of SMF-based networks. However, additionally, it is necessary to decrease the cost and energy per bit in order to provide economically attractive solutions. For this purpose, a smooth upgrade path has to be carried out as new integrated devices and system components are developed for Space Division Multiplexing (SDM). This thesis is concentrated on the planning and operation of the combined flexible WDM and SDM networks (i.e., Flex-Grid/SDM networks) proposing several strategies aimed at optimizing network resources usage with hardware complexity analysis. For this purpose, firstly, network problems are carefully studied and stated, and then, mathematical and/or heuristic algorithms are designed and implemented in an optical network simulator. Specifically, after an introduction to the thesis, chapter 2 presents the background and related work. Next, chapter 3 concentrates on the study of spatially fixed Flex-Grid/SDM networks, i.e., when a rigid number of spatial channels are reserved per allocated traffic demand. In its turn, chapter 4 studies the case of Spectrally-Spatially Flexible Optical Networks (SS-FONs), as the ones providing the upper-bound network capacity. Costs and hardware requirements implied on providing this flexibility are analyzed. Network nodes aimed at reducing the cost of SS-FONs are presented and evaluated in chapter 5. Finally, this thesis ends with the presentation of the main contributions and future research work in chapter 6.