Self-Healing Ring-Based Time-Sharing Passive Optical Networks

A new ring-based time-shared passive optical network (PON), with a self-healing function to prevent the occurrence of fiber-fault, has been proposed and investigated experimentally. By using the new optical line termination and single fiber path architecture, the proposed self-healing ring topology PON can be revived promptly under single fiber failure. The system performances of the proposed access network are also measured and discussed.     

The modified star-ring architecture for high-capacity subcarriermultiplexed passive optical networks

A modified star-ring architecture (MSRA) consisting of a star network on the upper level and many concatenated ring subnets on the lower level is proposed for subcarrier multiplexed passive optical network (SCM-PON). The upper level star network ensures high network capacity and its weakness in reliability is overcome by the concatenated ring subnets with self-healing capabilities. The self-healing function can be performed at remote nodes (RNs) by using optical switches (OS) to reconfigure the ring subnets if any link fails. Moreover, we design the cascade add/drop transceiver (CAT) structure in the lower level ring subnets to completely eliminate the optical beat interference (OBI) problem and achieve an OBI-free optical network. Finally, we set up an experimental network to demonstrate the feasibility of this cost-effective survivable structure     

Virtual optical self-healing ring network over star-configuredoptical cable plant using N×N arrayed waveguide grating

A method to implement optical self-healing ring networks in metropolitan and access areas where fibres have already been deployed in star shape is proposed. An experimental network operating at 2.5 Gbit/s is demonstrated     

A passive protected self-healing mesh network architecture andapplications

The self-healing mesh network architecture using digital cross-connect systems (DCSs) is a crucial part of an integrated network restoration system. The conventional DCS self-healing networks using logical channel protection may require a large amount of spare capacity for network components (such as DCSs) and may not restore services fast enough (e.g., within 2 s). The authors propose a passive protected DCS self-healing network (PPDSHN) architecture using a passive protection cross-connect network for network protection. For the PPDSHN architecture, network restoration is performed in the optical domain and is controlled by electronic working DCS systems. Some case studies have suggested that the proposed PPDSHN architecture may restore services within a two-second objective with less equipment cost than the conventional DCS self-healing network architecture in high-demand metropolitan areas for local exchange carrier networks. The proposed PPDSHN architecture may apply to not only the centralized and distributed control DCS network architectures, but also asynchronous, SONET and ATM DCS networks. Transparency of line rates and transmission formats makes the PPDSHN network even more attractive when network evolution is a key concern of network planning     

A novel passive protected SONET bidirectional self-healing ringarchitecture

Among SONET ring alternatives, the four-fiber bidirectional self-healing ring architecture (BSHR/4) has the highest available capacity and can work with today's systems with minimum change. A cost-effective implementation for a BSHR/4 which uses a totally passive ring as the protection ring of the BSHR/4 is presented. The ring uses a SONET ring to carry working traffic and a passive ring to carry protection traffic in case of network component failures. The passive ring, which is composed of optical switches and optical amplifiers, is essentially an optical add-drop protection ring. The optical signal add-drop is controlled by SONET add-drop multiplexers using existing SONET self-healing protocols. A SONET control scheme for this implementation is also discussed. The proposed BSHR/4 not only has a significant cost advantage over conventional implementations, but also can easily evolve from any two-fiber ring, with a minimum capital investment and offering twice the capacity     

Architectures for ATM network survivability

This article surveys the restoration architectures for asynchronous transfer mode (ATM) network survivability that have been actively studied in this decade. Network reliability is critical for recent and future networks that will advance the information era. Moreover, it is one of the biggest factors in designing and managing networks. Since the early telecom network era, many restoration systems have been developed for plesiochronous digital hierarchy (PDH), synchronous digital hierarchy (SDH), synchronous optical network (SONET), leased lines and so on; and they were surveyed in many papers and books. This article focuses on new restoration techniques for ATM networks. First, the requirement studies are introduced. This includes the scant results published on the influence of failure and the state of failure analysis. Next, restoration schemes are categorized and briefly introduced. Examples include centralized control, automatic protection switch (APS), self-healing ring (SHR), self-healing network (SHN) and failure resistant virtual path (FRVP). In order to achieve adequate restoration probability with minimum cost, a network design scheme is necessary; thus, network design issues are introduced. Finally, this article focuses on the issues, future work, and problems that remain to be solved.     

Restoration message transfer mechanism and restorationcharacteristics of double-search self-healing ATM network

The self-healing network is particularly interesting with regard to ATM networks, because the restoration time can be shortened by using the advantages of the ATM network. This paper studies a self-healing ATM network based on virtual path (VP) protection switching. First, a novel self-healing algorithm-the double-search self-healing algorithm-is proposed. It is shown that this algorithm can restore failed bidirectional VPs faster and find alternate VPs more effectively than existing self-healing algorithms. Second, it is shown that the restoration information for self-healing control (SHC) messages must be transferred by specific cells carrying the control and OAM information (Ic&o). Message parameters and a cell format are proposed. Third, evaluation of the restoration characteristics using the proposed self-healing algorithm by computer simulation indicates that good performance against a transmission link failure is obtained even in a large-scale network model with 110 nodes. The results also indicate that the VP group (VPG) method can improve the restoration time without reducing the restoration ratio     

Flexible synchronous broad-band subscriber loop system: opticalshuttle bus

A flexible, synchronous, broadband subscriber loop system called the optical shuttle bus is discussed. The emphasis is on the proposed design architecture and performance of a 1.8-Gb/s prototype system. The optical shuttle bus is constructed of multigigabit/second intelligent optical shuttle nodes (OSNs). The software-defined OSNs allow the bus to be configured as a synchronous transmission network with any topology and provides flexible channel allocation by means of a drop/insert/cross-connect function. The OSN can be configured as a highly reliable network by virtue of its self-healing functions such as line switch, bypass, and loop back. The proposed bus architecture has been successfully applied in a 1.8-Gb/s prototype in which three OSNs are connected by one 10-km and two 5-dm single-mode fibers in a ring configuration. Very compact and inexpensive equipment is realized by using high-speed ICs. Experimental results show the proposed architecture to be a powerful one for the realization of synchronous broadband subscriber loop systems     

A DWDM/SCM self-healing architecture for broad-band subscriber networks

A high-capacity dense wavelength-division multiplexing/subcarrier multiplexing (DWDM/SCM) network based on a self-healing star-bus-ring architecture (SBRA) is proposed and demonstrated. This architecture has a star subnet on the upper level to be a high-capacity infrastructure for the network, several bus subnets on the middle level to offer broad-band channels for multiwavelength signals, and many ring subnets on the lower level to serve a number of nodes. We design remote nodes and bidirectional wavelength add-drop multiplexers (WADMs) by using simple optical switches to reconfigure the network under link failure. We further employ M-quadrature amplitude modulation (M-QAM) and frequency shift-keyed (FSK) signals for downstream and upstream channels, respectively. The SBRA ensures an optical-beat-interference-free (OBI-free) and high-reliability optical network. Finally, we set up an experimental network to demonstrate the feasibility of the proposed architecture.     

WDM全光网SHAONET的快速自愈保护

基于波长路由的ＷＤＭ全光网是下一代高速宽带光纤网络的首选技术。ＳＨＡＯＮＥＴ是国内自主开发的第一个ＷＤＭ全光试验网平台,它采用了一种新型保护结构的ＯＡＤＭ,具有很强的自愈功能。本文阐述了ＳＨＡＯＮＥＴ中采用的快速自愈保护机制及其实现。     

All-optical four-fiber bidirectional line-switched ring

An all-optical four-fiber bidirectional line-switched ring (O-4F/BLSR) architecture is proposed. This new physical layer networking protocol uses wavelengths as tributaries and an optical supervisory channel to carry overhead information. Optical channels can be added and dropped from the ring, and virtual wavelength paths can be provisioned. Both node and link failures of a network can be protected through a two layer protection scheme. Protection switching within the optical multiplex section layer (OMS) restores failure caused by loss of optical continuity in a way similar to the SONET 4F/BLSR line switching. Protection switching within the optical channel layer restores single channel failure using 1:N protection. Test results show that the O-4F/BLSR can restore traffic in less than 50 ms. A self-healing, bandwidth efficient, and scalable all-optical transport network evolving from this O-4F/BLSR architecture is possible     

Control protocol and its performance analysis for distributed ATMvirtual path self-healing network

A restorable network comprised of a mesh of ATM virtual paths (AVPs) is expected to be superior to distributed SONET digital cross-connect self-healing networks in terms of restoration time. The paper presents a reliable protocol and evaluation of its performance for control information transfer in distributed AVP self-healing networks. Two error-recovery technologies for the data-link level (selective retransmission and go-back-N) in AVP networks are reviewed, and a model for evaluating the delay of the go-back-N method that has been used in existing terrestrial systems is derived analytically. The proposed analytic model is combined with a self-healing simulator for AVP mesh networks to evaluate the restoration time characteristics. Case study results for the worst-case scenario show that the total restoration time, including link-by-link error control for self-healing control messages, is expected to be less than 2 s, which is the time objective for complete restoration for a metropolitan LATA network. The results also show that the estimated average delay penalty for adding the link-by-link error recovery process is 7.5 ms for complete service restoration     

Architecture and functional requirements of control planes for automatic switched optical networks: experience of the IST project LION

This article focuses on architecture and functional requirements for control planes of automatic switched optical networks. Specifically, four different approaches for triggering the setup of optical connections have been reported. Furthermore, the article describes the testbed of the IST Project LION: the testbed, aimed at demonstrating some ASON functionalities, is composed by optical network elements (OADM and OXC provided by Siemens, Tellium, and Telecom Italia Lab) and IP routers (provided by Cisco).     

全球三网融合发展现状、挑战和趋势

电信和广电的融合在很多国家早已突破法规和政策瓶颈,开始实施电信与广电的双向准入。电信运营商技术上从采用ADSL、ADSL2/2＋和VDSL,逐渐过渡到光纤接入;而很多有线电视公司则采用DOCSIS3.0技术升级网络来提供三网融合业务;很多国家主要的电信运营商和有线电视网络公司都提供三重服务。目前电信运营商和有线电视提供商都面临网络电视的挑战。     

光纤用户接入网的可靠性研究

提出了研究光纤用户接入网可靠性的一般方法,探讨了光纤用户接入网的连通性,由网络生存性的角度提出了适用于光纤用户接入网的组网与保护方式。     

Survivable SONET networks-design methodology

A prototype software system that implements a methodology for the strategic planning of survivable interoffice networks is presented. The software system determines strategic locations and ring types for synchronous optical network ring placement. Two types of survivable network architectures are considered-1:1 diverse protection and SONET self-healing rings. The software considers three types of SONET self-healing rings-unidirectional, 2-fiber bidirectional, and 4-fiber bidirectional. Hubbing is assumed in all architectures. Inputs include nodes, links, connectivity, facility hierarchy, and multiyear point-to-point demands, together with the costs of fiber material and splicing, route mileage (installation), and multiplexors and regenerators of different rates. The outputs are a set of near-optimal rings based on cost, specifying the ring types and rates, fiber span sizes and counts, regenerator locations and speeds, the topology (set of links to be used), and the network cost. In addition, the software outputs the time in the planning period that each ring and fiber span should be installed     

An optical FDM-based self-healing ring network employing arrayedwaveguide grating filters and EDFA's with level equalizers

An optical frequency-division multiplexing (OFDM) based self-healing unidirectional ring network is designed and its performance is verified. It employs arrayed waveguide grating add/drop multiplexers (ADMs) and erbium-doped fiber amplifiers (EDFAs) with waveguide level equalizers in each remote node. The route diversity configuration is employed to make the network robust and bit loss-free route switching is performed. The level diagram reproducibility for each OFDM channel is guaranteed by the waveguide-level equalizers. Successful transmission performance confirms the effectiveness of the proposed system     

Multiple-availability-level ATM network architecture

Because of their high flexibility, ATM networks have the potential to achieve two objectives: switch cost reduction and multi-level network availability. For that purpose, this article proposes to use virtual circuit (VC) route self-healing schemes to achieve a multiple-availability-level ATM network. Flexible multi-QoS logical ATM network (Full-Net), a new concept for ATM networks, is now being studied at NTT Laboratories. Full-Net is a very flexible network design strategy for survivable networks that is based on a self-healing VC network. Defining several logical configurations of the VC network allows us to support multiple levels of network availability, simplifies the adaptation to future and unknown service requirements, and significantly reduces overall ATM network cost. Offering different levels of availability not only saves the network's resources, but also allows the network operator to provide its customers with services at the most appropriate cost. We introduce the advantages of VC route restoration for ATM networks, and compare virtual path (VP) level and physical level restoration strategies. We explain Full-Net's concept, propose a VC route self-healing scheme, and show the impact of the logical network configurations on network survivability and resource management     

Optical power limiting amplifier and its applications in an SONETself-healing ring network

The authors demonstrate an erbium-doped optical power limiting amplifier (OLA), study its noise characteristics, and discuss its application in the protection rings of a four-fiber, SONET self-healing interoffice ring network. System and network considerations are also presented. The feasibility of the network was tested by a system experiment using an OLA for up to 200-km conventional single-mode fiber transmission at a bit rate of 1.244 Gb/s (OC-24 line rate)     

基于多智能体深度强化学习的智能电网光网络切片方案

为了提高光网络对大规模、差异化电力业务的资源分配能力,降低大规模业务的算法训练时间,提出了一种基于多智能体深度确定性策略梯度算法的智能电网光网络资源分配方案。该方案考虑大规模和差异化电力业务,将智能电网光网络建模成多智能体系统,以最大化电网公司收益为目标,建立了智能电网光核心网络切片模型,进行网络资源分配优化,并采用条件判断映射,简化了优化问题。同时,把不同业务部署到不同智能体中进行运算,以降低训练时间,满足网络实时性需求。仿真结果表明,该算法具有更大的奖励、更低的成本、时延和训练时间。