Performance Management of Optical Transport Networks through Time Series Forecasting

To construct the future multimedia backbone network, wavelength-division multiplexing (WDM) optical path networks that support various transport protocols are required. This paper proposes an effective network protection strategy and management technologies for such networks.

40-Gbit/s ETDM Channel Technologies for Optical Transport Network

To accommodate big data, new technologies and features have started to be used in core network. Consequently, optical transport network has evolved towards Elastic Optical Network (EON). Despite the effort made towards efficient and reliable network management, interoperability problem in multi-vendor setting of the EON remains unsolved and it hinders the network management and monitoring. Hence, Network operators need to rely on the proprietary management solutions. This phenomenon poses complexity in network configuration, control, monitoring and management and also in turn results in higher Capital Expenditure (CAPEX) and Operational Expenditure (OPEX) for the service providers. In this paper, standard data definition model of network elements of EON is presented for configuration, management and monitoring purpose. Standard YANG data models for the network elements, namely, Reconfigurable Optical Add/drop Multiplexer (ROADM), Bandwidth Variable Transponder (BVT) and Optical amplifier (OA) are presented. The implementation scenario for the developed data definition models are demonstrated for managing state of the art EON. It is contended that the adoption of these standard YANG data models within the NETCONF protocol not only facilitates the network configuration and management, but also improves the multi-vendor interoperability in the control and management plane of the EON.

Chapter 3 - Optical Network Architecture Evolution

Protection system communications are increasing in importance because they enable optimal operation of power systems. Because of the high cost of communications systems in the past, protection systems had to be optimized to use minimum bandwidth and were often forced to rely on a single bit of information. A synchronous 64 kbps channel reserved exclusively for the most critical transmission lines was seen as the best-case scenario. Communications system developments over the last three decades have opened a deluge of information, with a single optical fiber now capable of carrying multiple terabits of data simultaneously. Modern protection systems face a totally different problem. Communications bandwidth is almost unlimited, but the channel must be shared with other users and may present multiple challenges, such as channel asymmetry, variable latency, path reconfiguration due to automated failure recovery, packet-based transport, and the need for system-wide time synchronization. This paper reports on an experimental investigation that uses coarse or dense wavelength division multiplexing (CWDM, DWDM) for applications in high-speed traveling-wave protection. The investigation was performed using the latest generation of carrier-grade optical transport network (OTN) equipment. The paper documents the performance, opportunities, and pitfalls associated with this application and outlines practical strategies for the seamless integration of protection systems with the latest generation of OTN technologies.

The development of wavelength-division multiplexing (WDM) all-optical transport networks is an interesting solution to increase the capacity of long-haul transmission systems and to solve the route-exhaust problems of metropolitan networks, driving down the cost of that traffic. Routing can be achieved using a transparent device able to select and interchange wavelengths, such as an all-optical wavelength converter. In this paper, an optical transport network over an embedded link located between Rome and Pomezia in Italy is emulated. The transmission has been realized along a WDM, 5 × 100 km long, dispersion managed link at 40 Gb/s. The in-line rerouting process has been controlled by means of an all-optical wavelength converter realized with a periodically poled lithium niobate waveguide. Moreover, a polarization- independent scheme for the converter has been exploited to allow the in-line signal processing. This scheme is based on the counterpropagation of TE and TM signal components along the same guide and results extremely compact. In this paper it is demonstrated that wavelength conversion and rerouting add no penalty with respect to the simple transmission along the embedded cable. This result seems to be another step toward the feasibility of true all-optical networks.

The technical advances in wavelength division multiplexing (WDM) techniques has made possible the introduction of optical technology into the path layer of the transport network. Besides the significant improvement in the transmission capacity, WDM technology allows the accomplishment of routing and switching functions directly in the optical domain. Thus Optical Cross-Connects (OXCs) can be realized with a throughput of a few hundreds of Gbit/s, so removing the bottleneck placed by electronic technology. The transport network node can be designed as an OXC interfacing a Digital Cross-Connect (DXC). Multi-Gigabit signals are directly routed in the optical network layer by the OXCs, while the DXCs provide demultiplexing to lower digital hierarchies and routing at the electrical level. The optical path layer can be designed so as to be transparent to the signal transmission format and speed. The aim of this paper is to assess the feasibility of transmitting sub-carrier multiplexed CATV channels in this optical path layer, by analysing the performance of the following transmission path: the CATV channels are generated in a production center, cross a geographical area through a transport network and an optical ring of a regional network, down to the access network and then to the customer.

The volume of traffic carried on the Optical Transport Network (OTN) is continuously growing, not only due to the increase of new services, new applications, and the number of both connected users and smart devices, but also owing to the rapidly growing Data Center Interconnect (DCI) market. As a result, telecom operators need to upgrade their transport networks to cope with these new traffic requirements. This tremendous increase in bandwidth demand will also introduce energy bottlenecks in OTNs. The telecommunication networks' significant Greenhouse Gas Emissions (GGE) is another challenge that must be addressed in OTN design and planning policies. Thus, energy-efficient OTN architectures are currently attracting the attention of telecom operators. The candidate OTN architectures are: (1) the conventional Dense Wavelength Division Multiplexing (DWDM) fixed grid with high Single Line Rates (SLRs); (2) the conventional DWDM fixed grid adopting Mixed Line Rates (MLRs); and (3) the Elastic Optical Network (EON) or flexigrid-based architecture which is enabled by the Optical Orthogonal Frequency Division Multiplexing (O-OFDM) technique. This paper evaluates the power consumption of the abovementioned OTN architectures under different traffic loads and patterns, as well as different network physical topologies. In order to perform the evaluation, new heuristic algorithms are specifically developed for the green design and planning of data center optical interconnects.

This paper addresses the management of photonic networks. It presents the first achievements of the ACTS-MEPHISTO project. The project's general objective is to extend the principles of network management (TMN) to generic all-optical networks, in which wavelength division multiplexing (WDM) will be implemented far transmission and routing. This includes the development of information models for optical networks and network elements, of management applications and test platforms to demonstrate fault, configuration and performance management of optical networks, and the promotion of the developed models within ACTS and standardisation bodies. The functional architecture and early information models for the management of optical networks and network elements are described.

Network Function Virtualization (NFV) has changed the way operators can provision network services. Decoupling network functions from dedicated hardware and running them on software, on top of commodity servers and switches, not only helps operators have more flexible and easy-to-manage networks, but also reduces their capital and operational expenditures. This is especially true for incoming 5G services, characterized by ultra-low latency, high reliability and bandwidth requirements. To satisfy these challenging requirements, multi-layer optical networks based on Optical Transport Network (OTN) over wavelength division multiplexing (WDM) are being deployed in the metro segment to support 5G services. In addition, the possibility to equip metro nodes with computing capabilities, enabled by new paradigms such as CORD (Central Office Re-architected as a Datacenter) is being exploited. In this scenario, an efficient placement of Virtual Network Functions (VNFs) for Service Chain (SC) provisioning within the metro network is needed, and different VNF placement strategies can lead to different costs for network operators. In this paper we analyze the impact of different VNF placement strategies on the optical metro network cost, considering specific Service Level Agreement (SLA) requirements, expressed in terms of service blocking probability. We provide a cost model which takes into consideration both capital and operational expenditures. Through extensive numerical results, we quantify the impact of using a cost-effective VNF placement strategy in decreasing network cost while meeting the desired SLA performance.

Elastic optical network (EON) is a promising candidate for the next generation optical transport network because of its high spectrum efficiency and flexible spectrum allocation. However, to migrate from today’s dense wavelength division multiplexing (DWDM) network to EON, optical nodes such as reconfigurable optical add/drop multiplexers (ROADMs) should be replaced with the ones with expensive flexi-grid wavelength selective switches (WSSs). Thus, whether and how today’s optical network will be evolved to EON is still under debate. Meanwhile, with the technical maturity of optical super-channels that transmit bit rates at the level of 1 Tb/s, super-channels are expected to dominate the future optical transport network because of their attractiveness of high spectrum efficiency and superior cost effectiveness. In this paper, we propose a new quasi-coarse wavelength division multiplexing (Quasi-CWDM) optical network architecture that is compatible to today’s WDM network in spectrum operation, while still maintaining the flexibility of adaptation between the bit rate and the transparent reach of an optical super-channel, but not requiring expensive flexi-grid WSSs. Specifically, the Quasi-CWDM optical network employs large fixed frequency grids, whose spacing falls between the traditional CWDM and DWDM, e.g., 200 GHz or 400 GHz. To maintain the flexibility between the bit rate and the transparent reach of an optical super-channel, different modulation formats are chosen according to channel physical distances. To minimize network hardware cost and maximize carried user traffic demand, we develop a mixed integer linear programming (MILP) model and a heuristic algorithm that can efficiently groom upper-layer IP traffic onto the optical layer by optical super-channels. We compare the design based on the Quasi-CWDM network to those based on the DWDM network and the advanced EON. It is found that the proposed Quasi-CWDM network has a much lower hardware cost than the other two types of networks, while achieving spectrum efficiency close to EON.

The ever-developing interest of present day society for information with enhanced execution over longer separations have made the system complex in terms of architecture, technologies, Network Elements, communication between Network Elements, security and signaling control. Equipment Management as a segment of Network Management System gives administrators the capacity to control general operation of the NEs, superintend interaction among NEs and to upper layer administration framework, thus automating the task of managing complex network. This paper presents the role of Equipment Management in Optical Transport Network and some of its challenges.

Due to widespread applications and rapid development of cloud computing and Internet services, hyperscale data centers have experienced an unprecedented demand for networking. Data center networks are required not only to handle fast-growing traffic, which doubles almost every one to two years, but also to provide high flexibility and availability to support rapidly changing businesses as well. Therefore, hyperscale data center networks have become one of the main drivers for optical interconnect technologies in recent years. In this article, technologies for scaling optical interconnects for inter-data center interconnects (DCIs) are presented. We first describe hyperscale data center network architectures and requirements, as well as the differences between carrier’s optical transport networks and DCI optical networks, with the main focus on metro-DCI and campus-DCI networks. The scale and fast growth rates of DCI networks require innovations not only in data plane technologies but also in control and management planes as well. In data planes, high-capacity flexible coherent technology, pluggable wavelength-division-multiplexing (WDM) optical transponders, including 100G direct-detection four-level pulse-amplitude modulation (PAM4) and coherent 400ZR/800ZR, and flex-grid and disaggregated reconfigurable optical add-drop multiplexer (ROADM) optical networks are described. Control and management planes are an integral part of optical transport networks and crucial for effectively operating DCI networks. We show that standard protocols, data models, and modular design of a software platform are essential to building a scalable open and disaggregated optical network, which is fundamental to enabling high automation and intelligence in an optical network. An example control and management platform is discussed in detail. With current fiber capacity approaching the nonlinear Shannon limit, challenges to further scale DCI networks and some potential technologies to support ever-increasing traffic growth are discussed at the end.

The explosive increase in data traffic requires networks to provide higher capacity and long-haul transmission capabilities. This paper introduces new results on high-order modulation and efficient Digital Signal Processing algorithms to reduce various transmission limitations in coherent receiving systems. Polarization Division Multiplexed Quadrature Phase Shift Keying (PDM-QPSK) is deployed to reach high bit rates, provides modified digital clock recovery, and allows BER-Aided Constant Modulus Algorithm (BA-CMA) equalising. A Soft Decision-Forward Error Correction (SD-FEC) algorithm and a joint scheme with timing recovery and adaptive equaliser are used to achieve better performance. A compact coherent transceiver is also developed. These techniques have been applied in the largest 100 G Optical Transport Network (OTN) deployment in the world, the backbone expansion project for Phase 3 of the China Education and Research Network (CERNET), with a total transmission length of 10 000 km.

In designing the backbone network for the province of East Kalimantan using Dense Wavelength Division Multiplexing (DWDM) and Optical Transport Network (OTN) devices which cover 10 districts and cities consisting of 34 segments, of which 34 segments consist of 10 OTN DWDM sites and 16 Optical Land Amplifier sites ( OLA). From the results of the design and simulation of the backbone network, it was found that the value of the Optical Link Power Budget (OLPB) < 50 dBm where this value is the ideal value in deploying a DWDM OTN backbone network, and the range of the Optical Signal Noise Ratio (OSNR) is between 20 dBm < OSNR < 40 dBm, which is the ideal value for OSNR, and has an Optical Rise Time Budget (ORTB) < 60 ps, and also has a segment margin system of > 7 dB.