Service level agreement and provisioning in optical networks

This article proposes a service level agreement applied to the optical domain (O-SLA), which is expected to be the near- and long-term network technology of the great bandwidth capacity offered by optical devices. After an exposition of the rationale behind an optical SLA, parameters that could be included in this O-SLA, as well as their values for four classes of services are proposed. Different client (wavelength or subwavelength) and service types (from leased wavelength to bandwidth on demand) are distinguished when necessary. The last part of this article presents issues related to the provisioning of services emanating from this O-SLA.     

业务光网络中光服务等级协定的研究

从业务光网络的角度对比服务等级协定(SLA)定义了光服务等级协定(O-SLA)的框架结构,在此基础上重点分析了O-SLA协商机制并提出一种动态协商的概念,对动态协商机制的实现流程进行了分析研究.随后总结了O-SLA得以有效实施的关键技术,并提出一种支持区分服务的O-SLA实施流程,此流程对于向端用户提供可定制化的光层业务提供了一种新思路.     

Service level agreements on IP networks

This paper provides an overview of service level agreements (SLAs) in IP networks. It looks at the typical components of an SLA and identifies three common approaches that are used to satisfy SLAs in IP networks. The implications of using the approaches in the context of a network service provider, a hosting service provider, and an enterprise are examined. While most providers currently offer a static insurance approach toward supporting SLAs, the schemes that can lead to more dynamic approaches are identified.     

Routing,modulation level and spectrum allocation with dynamic modulation level conversion in elastic optical networks

Elastic optical network is introduced as a promising technology to provide multi-bitrate-friendly data transmission in the optical layer. Elastic optical networks are based on flexible modulation format conversion, which can make more efficient use of spectrum resources than current fix-grid WDM networks. In this paper, we define the routing, modulation level and spectrum resource allocation (RMLSA) problem and then propose two novel dynamic modulation level conversion (MLC) enabled RMLSA algorithms. Numerical simulations are conducted to compare the performance of the path modulation level conversion (Path-MLC) and link modulation level conversion (Link-MLC) with different MLC thresholds with K-shortest paths RSA in terms of blocking rate, occupied spectrum and the number of MLCs across two topologies. The results verify that the Link-MLC with unlimited MLC achieves the lowest blocking rate and moderate spectrum utilization at the expense of intermediate node modulation conversions in two topologies. Smaller MLC threshold has higher blocking rate and occupied less spectrum resource. The results also suggest that the Path-MLC approach is more resource efficient than the Link-MLC with relatively higher blocking rate, and this method maybe more preferable in the networks with tight budget and/or energy constraints.     

Survivability in optical networks

Survivability, the ability of a network to withstand and recover from failures, is one of the most important requirements of networks. Its importance is magnified in fiber optic networks with throughputs on the order of gigabits and terabits per second. This article takes a look at the techniques used to achieve survivability in traditional optical networks, and how those techniques are evolving to make next-generation WDM networks survivable.     

光网络的进展研究

光传送网是指光信道接入点所定界的传送网络。光传送网络的物理层采用光纤作为传输媒介，光传送网为客户层信号在很大范围内提供包括传送、复用、路由、管理、抗故障等功能。光传输技术经历了PDH、SDH到WDM的发展过程。在90年代，SONET/SDH网络在容量、可靠性和网络传送效率方面都得到迅速提高。光传送网主要提供如下功能：不同网络客户的透明传送、不同管理域的互联、光信道连接和保护、性能监测和告警监视、网络管理。目前光网络的单信道的传送速率(图1)和网络的传送容量在迅速增加，以满足不断增长的互联网的业务需求。单纤复用的…     

光网络中的动态可重构的光分插复用技术

动态可重构的光分插复用器(ROADM)在光通信网络与传感网络中有重要的应用,而且是对目前正在使用的非重构的光网络升级的核心技术之一.超大规模、高可靠性的传感器网络对可重构的OADM需求尤其迫切.结合本课题组承担的863项目的研究成果,对该技术进行介绍.     

Developments in optical access networks

Optical fibre access network technology has become more complex over the last few years with bit rates steadily increasing. PONsystems are available with bit rates in the range 155 Mbit/s to, currently, 622 Mbit/s. Newly designed systems, both PON andpoint-to-point, will allow this trend to continue with 2.5 Gbit/s systems becoming practicable in the near future.With this increase in technology has come an increase in the opportunities for fibre systems to cost-reduce more of the network,including the metro space – a fact which increases the appeal of the technology.Some of the newer PON systems are being designed using Ethernet as the underlying technology with a promise of reducing theprice of the technology still further. How this will occur in practice, however, is still unclear.What is certain is that optical access technologies are expanding and are sure to find openings in real networks in the foreseeablefuture.     

城域光网络生存性的研究

从分析目前常用的网络保护和恢复方法出发,提出将路由算法引入到光网络保护中去:通过动态路由算法,网络动态计算源、宿节点间最佳工作路径.通过将虚连接引入面向连接的光网络,建立保护路径.在消除为工作路径预留独享资源的同时,简化了保护倒换流程,缩短了故障恢复时间,提高了网络资源利用率.     

Tunable lasers in optical networks

Tunable lasers have been the subject of considerable interest ever since the start of the wavelength division multiplexing (WDM) revolution. In this paper, we bring together views on tunable lasers from different types of companies in the value chain, from operators to laser manufacturers. The purpose of the paper is to give an overview of the state of the art in both deployment and development, as well as to try to predict trends over the coming years.     

Eco-sustainable routing in optical networks

It is quite easy to foresee that in the next years, the future generation ultra-high speed network infrastructures and equipments will be no longer constrained only by their pure transport capacity, but also by their energy consumption costs and environmental effects. In particular, large network infrastructures are now widely recognized to play a fundamental role in the emission of greenhouse gases in the atmosphere, significantly affecting the environmental sustainability of new evolutions in network architectures as well as technological developments in communication devices. In this paper, a novel eco-sustainable routing and wavelength assignment algorithm, based on shortest path routing with an adaptive link weighting function relying on an extension of the OSPF-TE protocol to convey carbon footprint information, has been proposed to decrease the network ecological impact while balancing the traffic load and maintaining acceptable connection-blocking rate. The trade-off between load balancing and carbon footprint is also analyzed to evaluate the effectiveness of the proposed strategy within the context of a real world network.     

Recovery in multilayer optical networks

The integration of different network technologies into a multilayer network, as in Internet-based networks carried by optical transport networks (OTNs), creates new opportunities but also challenges with respect to network survivability. In different network layers, recovery mechanisms that are active can be exploited jointly to reach a more efficient or faster recovery from failures. This interworking is also indispensable in order to overcome the variety of failure scenarios that can occur in the multilayer-network environment. A well-considered coordination between the different layers and their recovery mechanisms is crucial in order to attain high performance recovery. This paper provides an overview of multilayer recovery issues and solutions in an Internet protocol (IP)-over-optical-network environment, which is illustrated by quantitative case studies.     

Waveband switching in optical networks

The rapid advances in dense wavelength-division multiplexing technology with hundreds of wavelengths per fiber and worldwide fiber deployment have brought about a tremendous increase in the size (i.e., number of ports) of photonic cross-connects, as well as in the cost and difficulty associated with controlling such large cross-connects. Waveband switching (WBS) has attracted attention for its practical importance in reducing the port count, associated control complexity, and cost of photonic cross-connects. We show that WBS is different from traditional wavelength routing, and thus techniques developed for wavelength-routed networks (including, for example, those for traffic grooming) cannot be directly applied to effectively address WBS-related problems. We describe two multigranular OXC architectures for WBS. By using the multilayer MG-OXC in conjunction with intelligent WBS algorithms for both static and dynamic traffic, we show that one can achieve considerable savings in the port count. We also present various WBS schemes and lightpath grouping strategies, and discuss issues related to waveband conversion and failure recovery in WBS networks.     

Service management in intelligent networks

Six basic categories of management functions are defined and described: configuration management, fault management, performance management, accounting management, security management, and planning. A network service model that encompasses these functions is presented, and some management issues are addressed. Two examples of service management are examined: network service provisioning and customer network service management     

Real-time optical spectrum monitoring in filterless optical metro networks

Photonic Network Communications - A novel method for disaster management using free space optical link is proposed in this paper. Free space optics recently gained great attention since it has...     

高速光纤网络中的超短光脉冲产生技术

文章综述了高速光纤网络中的超短光脉冲产生技术及其进展,讨论了实现高效率脉冲压缩的途径,介绍了作者利用阶梯色散渐减光纤环镜代替色散渐减光纤环镜的光脉冲压缩方法的研究成果.数值计算表明,该方法的压缩效果与色散渐减光纤环镜的压缩效果基本一致,解决了色散渐减光纤制作和选择困难的问题,给系统设计带来了方便.     

新一代的光纤通信网--全光网

综述了全光网的基本概念，并介绍了全光网的网络拓扑结构、波长路由等关键技术和全光网的发展趋势。     

Coherent optical CDMA networks

Recent work in optical code-division multiple access (CDMA) is reviewed, progressing from incoherent to coherent techniques. It is shown that under appropriate conditions, coherent CDMA can in principle rival wavelength-division multiplexing (WDM) in terms of aggregate network throughput. Furthermore, it is shown that at high data rates, some of the components for WDM are coherent CDMA networks are nearly identical, indicating a similarity between the two approaches. CDMA retains a coding aspect which may prove attractive in security applications