Resource Management in Survivable Multi-Granular Optical Networks

The last decade witnessed a wild growth of the Internet traffic, promoted by bandwidth-hungry applications such as Youtube, P2P, and VoIP. This explosive increase is expected to proceed with an annual rate of 34% in the near future, which leads to a huge challenge to the Internet infrastructure. One foremost solution to this problem is advancing the optical networking and switching, by which abundant bandwidth can be provided in an energy-efficient manner. For instance, with Wavelength Division Multiplexing (WDM) technology, each fiber can carry a mass of wavelengths with bandwidth up to 100 Gbits/s or higher. To keep up with the traffic explosion, however, simply scaling the number of fibers and/or wavelengths per fiber results in the scalability issue in WDM networks. One major motivation of this dissertation is to address this issue in WDM networks with the idea of waveband switching (WBS). This work includes the author\u27s study on multiple aspects of waveband switching: how to address dynamic user demand, how to accommodate static user demand, and how to achieve a survivable WBS network. When combined together, the proposed approaches form a framework that enables an efficient WBS-based Internet in the near future or the middle term. As a long-term solution for the Internet backbone, the Spectrum Sliced Elastic Optical Path (SLICE) Networks recently attract significant interests. SLICE aims to provide abundant bandwidth by managing the spectrum resources as orthogonal sub-carriers, a finer granular than wavelengths of WDM networks. Another important component of this dissertation is the author\u27s timely study on this new frontier: particulary, how to efficiency accommodate the user demand in SLICE networks. We refer to the overall study as the resource management in multi-granular optical networks. In WBS networks, the multi-granularity includes the fiber, waveband, and wavelength. While in SLICE networks, the traffic granularity refers to the fiber, and the variety of the demand size (in terms of number of sub-carriers)

Framework for waveband switching in multigranular optical networks: part I-multigranular cross-connect architectures

Optical networks using wavelength-division multiplexing (WDM) are the foremost solution to the ever-increasing traffic in the Internet backbone. Rapid advances in WDM technology will enable each fiber to carry hundreds or even a thousand wavelengths (using dense-WDM, or DWDM, and ultra-DWDM) of traffic. This, coupled with worldwide fiber deployment, will bring about a tremendous increase in the size of the optical cross-connects, i.e., the number of ports of the wavelength switching elements. Waveband switching (WBS), wherein wavelengths are grouped into bands and switched as a single entity, can reduce the cost and control complexity of switching nodes by minimizing the port count. This paper presents a detailed study on recent advances and open research issues in WBS networks. In this study, we investigate in detail the architecture for various WBS cross-connects and compare them in terms of the number of ports and complexity and also in terms of how flexible they are in adjusting to dynamic traffic. We outline various techniques for grouping wavelengths into bands for the purpose of WBS and show how traditional wavelength routing is different from waveband routing and why techniques developed for wavelength-routed networks (WRNs) cannot be simply applied to WBS networks. We also outline how traffic grooming of subwavelength traffic can be done in WBS networks. In part II of this study [Cao , submitted to J. Opt. Netw.], we study the effect of wavelength conversion on the performance of WBS networks with reconfigurable MG-OXCs. We present an algorithm for waveband grouping in wavelength-convertible networks and evaluate its performance. We also investigate issues related to survivability in WBS networks and show how waveband and wavelength conversion can be used to recover from failures in WBS networks

Optical architectures for high performance switching and routing

This thesis investigates optical interconnection networks for high performance switching and routing. Two main topics are studied. The first topic regards the use of silicon microring resonators for short reach optical interconnects. Photonic technologies can help to overcome the intrinsic limitations of electronics when used in interconnects, short-distance transmissions and switching operations. This thesis considers the peculiarasymmetric losses of microring resonators since they pose unprecedented challenges for the design of the architecture and for the routing algorithms. It presents new interconnection architectures, proposes modifications on classical routing algorithms and achieves a better performance in terms of fabric complexity and scalability with respect to the state of the art. Subsequently, this thesis considers wavelength dimension capabilities of microring resonators in which wavelength reuse (i.e. crosstalk accumulation) presents impairments on the system performance. To this aim, it presents different crosstalk reduction techniques, a feasibility analysis for the design of microring resonators and a novel wavelength-agile routing matrix. The second topic regards flexible resource allocation with adaptable infrastructure for elastic optical networks. In particular, it focus on Architecture on Demand (AoD), whereby optical node architectures can be reconfigured on the fly according to traffic requirements. This thesis includes results on the first flexible-grid optical spectrum networking field trial, carried out in a collaboration with University of Essex. Finally, it addresses several challenges that present the novel concept AoD by means of modeling and simulation. This thesis proposes an algorithm to perform automatic architecture synthesis, reports AoD scalability and power consumption results working under the proposed synthesis algorithm. Such results validate AoD as a flexible node concept that provides power efficiency and high switching capacity

A survey on OFDM-based elastic core optical networking

Orthogonal frequency-division multiplexing (OFDM) is a modulation technology that has been widely adopted in many new and emerging broadband wireless and wireline communication systems. Due to its capability to transmit a high-speed data stream using multiple spectral-overlapped lower-speed subcarriers, OFDM technology offers superior advantages of high spectrum efficiency, robustness against inter-carrier and inter-symbol interference, adaptability to server channel conditions, etc. In recent years, there have been intensive studies on optical OFDM (O-OFDM) transmission technologies, and it is considered a promising technology for future ultra-high-speed optical transmission. Based on O-OFDM technology, a novel elastic optical network architecture with immense flexibility and scalability in spectrum allocation and data rate accommodation could be built to support diverse services and the rapid growth of Internet traffic in the future. In this paper, we present a comprehensive survey on OFDM-based elastic optical network technologies, including basic principles of OFDM, O-OFDM technologies, the architectures of OFDM-based elastic core optical networks, and related key enabling technologies. The main advantages and issues of OFDM-based elastic core optical networks that are under research are also discussed

Management of Spectral Resources in Elastic Optical Networks

Recent developments in the area of mobile technologies, data center networks, cloud computing and social networks have triggered the growth of a wide range of network applications. The data rate of these applications also vary from a few megabits per second (Mbps) to several Gigabits per second (Gbps), thereby increasing the burden on the Inter- net. To support this growth in Internet data traffic, one foremost solution is to utilize the advancements in optical networks. With technology such as wavelength division multiplexing (WDM) networks, bandwidth upto 100 Gbps can be exploited from the optical fiber in an energy efficient manner. However, WDM networks are not efficient when the traffic demands vary frequently. Elastic Optical Networks (EONs) or Spectrum Sliced Elastic Optical Path Networks (SLICE) or Flex-Grid has been recently proposed as a long-term solution to handle the ever-increasing data traffic and the diverse demand range. EONs provide abundant bandwidth by managing the spectrum resources as fine-granular orthogonal sub-carriers that makes it suitable to accommodate varying traffic demands. However, the Routing and Spectrum Allocation (RSA) algorithm in EONs has to follow additional constraints while allocating sub-carriers to demands. These constraints increase the complexity of RSA in EONs and also, make EONs prone to the fragmentation of spectral resources, thereby decreasing the spectral efficiency. The major objective of this dissertation is to study the problem of spectrum allocation in EONs under various network conditions. With this objective, this dissertation presents the author\u27s study and research on multiple aspects of spectrum allocation in EONs: how to allocate sub-carriers to the traffic demands, how to accommodate traffic demands that varies with time, how to minimize the fragmentation of spectral resources and how to efficiently integrate the predictability of user demands for spectrum assignment. Another important contribution of this dissertation is the application of EONs as one of the substrate technologies for network virtualization

OSNR Aware Composition of an Open and Disaggregated Optical Node and Network

A function programmable optical network has been recently proposed to enhance the flexibility of an optical transport based on architecture-on-demand (AoD). The flexible synthesis of optical node architectures provided by AoD enables an open and disaggregated optical layer thanks to the available deep programmability. However, previous studies have focused on how to synthesize a single node out of switching function blocks, thus neglecting the optical signal-to-noise ratio (OSNR) impact, power imbalance effects due to the diverse set of devices traversed per input–output configuration, and network-wide implications. In this work, we present an optical network-wide function synthesis (ONetFuS), which is an algorithm to compose AoD nodes that consider placement and configuration of both switches and amplifiers. ONeFuS minimizes OSNR degradation and deviation across channels and offers enhanced power balance performance. Moreover, ONetFuS addresses multiple-node scenarios to investigate cascading, transmission distance, and networking effects. We compare the number of optical cross-connections computed by our proposal against solutions in the literature. Results in network scenarios, including the number of components, power balance, OSNR variations, and OSNR penalty reductions, prove the suitability of our proposed ONetFuS for open and functional programmable optical networks

Microring-Resonator-Based Switch Architectures for Optical Networks

Integrated silicon photonics provides a promising platform for chip-based, high-speed optical signal processing due to its compatibility with complementary metal-oxide semiconductor (CMOS) fabrication processes. They are attracting significant research and development interest globally and making a huge impact on green information and communication technologies, and high-performance computing systems. Microring resonators (MRRs) show the versatility to implement a variety of network functions, compact footprint, and complementary metal-oxide semiconductor compatibility, and demonstrate the viability applied in photonic integrated technologies for both chip level and board-to-board interconnects. Furthermore, MRRs have excellent wavelength selection properties and can be used to design tunable filters, modulators, wavelength converters, and switches that are critical components for optical interconnects. The research work of this dissertation is focused on investigating how to develop MRR-based switches and switch architectures for possible applications not only in optical interconnection networks but also in flexible-grid on-chip networks for optical communication systems. The basic properties and performances of the MRR switches and the MRR switch architectures related to their applications in the networks are examined. In particular, how to design and how to configure high performance, bandwidth variable, low insertion loss, and weak crosstalk MRR-based switches and switch architectures are investigated for applications in optical interconnection networks and in flexible-grid on-chip networks for optical communication systems. The works include several parts as follows. The physical characteristics of microring resonator switching devices are thoroughly analyzed using a model based on the field coupling matrix theory. The spectral response and insertion loss properties of these switching elements are simulated using the developed model. Then we investigate the optimal design of high-order MRR-based switch devices. Spectral shaping of the passbands of microring resonator switches is studied. Multistage high-order microring resonator-based optical switch structures are proposed to achieve steep-edge flat-top spectral passband. Using the transfer matrix analysis model, the spectral response behaviors of the switch structures are simulated. The performances of the proposed multistage high-order microring resonator-based optical switch structures and the high-order microring-resonator-based optical switch structures without stages are studied and compared. Two types of MRR-based switch architectures are proposed to realize variable output bandwidths varying from 0 to 4 THz. One consists of 320, 160, and 80 third-order MRR switches with -3 dB passband widths of 12.5, 25, and 50 GHz, respectively. Another one is two-stage switch structure. In the first stage there are 4 third-order MRR switches with the passband widths of 1 THz. In second stage, there are 80, 40, 20 third-order MRR switches with the passband widths of 12.5, 25, and 50 GHz, respectively. Their insertion losses and crosstalks in the worst cases are numerically analyzed and compared in order to show the feasibility for the architectures to be applied in flexible optical networks. MRR-based bandwidth-variable wavelength selective switch architectures with multiple input and output ports are proposed for flexible optical networks. The light transmission behaviors of a 1 by N MRR-based WSS are analyzed in detail based on numerical simulation using transfer matrix theory. Two types of N by N MRR-based WSS architectures consisting of MRR-based WSSs and MRR-based WSSs, and MRR-based WSSs and optical couplers are proposed. The performances of the proposed architectures are studied. Scalable optical interconnections based on MRRs are proposed, which consist mainly of microring resonator devices: microring lasers, microring switches, microring de-multiplexers, and integrated photo-dectors. Their throughput capacities, end-to-end time latencies, and transmission packet loss rates are evaluated using OMNet++. In summary, the research of the dissertation contributes to develop high performance, variable bandwidth, low insertion loss, and low crosstalk MRR-based optical switches and switch architectures to adapt to dynamic source allocation of flexible-grid optical networks