传输网络光缆物理路由的规划

光传输网络的突出优势就是组网，自愈环是其主要拓扑结构，网络具有自愈保护功能．本地传输网络一般按骨干层，汇聚层和接入层的功能结构组织，在层次网络结构中，如何组织光缆路由。本文利用分枝限界法解决了自愈环光缆路由的速择问题，提出了分层网络光缆路由规划的数学模型。     

规划SDH自愈环过程中的光缆路由策略

在规划SDH自愈环的过程中，环的光缆路由策略是一个比较复杂的问题。本文提出了一种基于TSP的改进算法，这种算法在考虑容量分配与否两种情况下，综合考虑了网络规划设计过程中可能出现的几种实际情况，对于规划SDH自愈环结构和设计生存性网络具有一定的参考价值。     

规划SDH自愈环过程中的光缆路由策略

在规划ＳＤＨ自愈环的过程中，环的光缆路由策略是一个比较复杂的问题，本文提出了一种基于ＴＳＰ的改进算法，这种算法在考虑容量分配与否两种情况下，综合考虑了网络规划设计过程中可能出现几种实际情况，对于规划ＳＤＨ自愈环结构和设计生存性网络具有一定的参考价值。     

基于无环替代重路由的无线Mesh网络自愈策略研究

无线Mesh网络的链路不可靠特性容易造成网络的不稳定和转发不连续,前摄性重路由可以解决这一问题。该文对基于无环替代重路由的无线Mesh网络自愈策略进行研究,提出了基于无环替代的AODV路由AODV-LFA,仿真实验表明AODV-LFA比AODV具有更强的自愈性能。     

SDH自愈环的互连互通研究

文章简要介绍了SDH网络保护方式,提出了自愈环互连互通的准则和结构,重点对SDH自愈环互连互通的具体结构及工作原理作了分析说明;最后提出了接入层网络结构优化的基本原则,并举例分析,为接入层网络结构优化提供了参考。     

中国联通加快建设全国长途光缆传输网

据悉,中国联通公司目前正在抓紧建设全国部分城市长途局间光缆传输网工程。工程将采用DWDM及SDH等先进的光缆传输手段,建成一个高层次的光缆传输网络。尤其是在我国的东部沿海地区和经济发达城市之间,将逐步建成以自愈环为主结构的多个可互相保护、互为迂回的光缆传环网,从而保证网络传输的安全可靠。     

通过光层实现IP over DWDM的业务保护

在过去由ＳＤＨ设备和ＤＷＤＭ设备组成的网络中 ,一般是利用ＳＤＨ设备形成的逻辑自愈环来实现业务保护的 ,方法简单且技术成熟 ,同时 ,由于这是在ＤＷＤＭ客户层的ＳＤＨ层面实现的自愈恢复 ,所以对ＤＷＤＭ系统没有特殊的要求。而作为ＤＷＤＭ客户层的路由器设备的业务恢复是靠额外路由的重新获得来实现业务保护的 ,这种路由的重新获得往往需要进行路由的重新计算分配 ,其时间是秒级甚至分钟级的 ,不符合网络电信级的运营要求 (ＳＤＨ网络的自愈恢复时间为毫秒级 )。同时 ,为了保证多个路由的存在 ,路由器上往往需要配置多个光口 ,而目前…     

要闻集锦

·日前，亚太2号光缆在上海开通。这是由中国电信、中国联通、中国网通与亚太地区的主要国际通信公司共同发起建设的，其中发起方26家，参与方45家。亚太2号光缆网络是亚太地区目前容量最大、登陆点最多、技术最先进且具有自愈恢复功能的环形结构网络。·中天科技股份有限公司生产的海底光缆在“中国电信崇明岛海缆登陆站———上海第三延伸路由光传输系统工程”中中标。这是具有自主知识产权的海底光缆在国家一级干线中标，表明我国海底光缆已达到国际先进水平。·上海市数字电视联合实验室于日前正式成立，同时发布《上海市数字电视终端接…     

一个特殊的SDH自愈环

SDH环是目前所有本地传输网用得最多的一种网络结构，它能对网上的承载业务提供迅速、可靠的保护。但在某些特殊情况下，我们在光路段无法提供迂回路由的光路，使网络的安全性大打折扣。以深圳本地传输网中的一个链型子网的改造为例，说明了我们可以采用不同的传输媒介来实现SDH环的自愈保护功能。     

SDH自愈网与自愈环

介绍了SDH自愈网的自愈环结构,说明了其优越性,并以4纤双向复用段倒换环为例,对自愈环的具体结构和工作原理进行分析说明,对4种主要的自愈环结构进行了性能比较,分析了自愈环在网络中的可行性。     

基于选发选收方案的OLP系统的设计与实现

基于选发选收光开关方案的光线路保护(OLP)系统满足SDH系统、DWDM系统等多种光传输系统的保护要求,可以有效提高整个光网络的生存能力.保护系统采用模块化的硬件结构和成熟的电信网管架构,实现了光传输系统中光线路的保护恢复、状态监测和路由调度等功能,提高了系统的可靠性和稳定性.     

省内干线传送网IP化之路

业务全面IP化、网络全面宽带化,成为这个时代的两大方向,并在省内干线传送网领域形成了富有激情的碰撞。“面向全IP业务的光传送网”显示出越来越明晰的框架,引领着最新的技术潮流。从未来来看,网络的IP化、扁平化不可逆转,省内干线传送网络最终会成为IP over Optical的架构。     

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     

光纤自动切换保护系统的应用探讨

分析光纤自动切换保护系统的原理,以我公司为例,在光传输网络主要路由上,接入光纤自动切换保护器,利用保护器构建出光纤保护网络,当被保护的光纤发生故障中断或者衰耗增大导致通信传输质量下降时,光纤线路自动切换保护技术却能使网络进行实际切换,用恢复机制作为第二道防线对付网络范围的故障和失效,恢复通信的畅通,从而增强了我公司通信网络的可靠性。     

面向单纤100 Tbit/s容量的光传输技术

随着信息社会对通信需求的急剧增长,运营商对骨干网传输容量进行扩展的需求日益迫切。首先对单纤100 Tbit/s容量的光传输技术的背景进行了简单介绍;接着对近年来国内外超大容量单模单纤光传输实验进行了比较;之后详细分析了实现单纤100 Tbit/s容量光传输系统的技术路线,并重点介绍了在国内首次实现的C/L 波段100.2 Tbit/s 超大容量双偏振DFT-S 128QAM OFDM 信号传输 80 km G.652 光纤的系统实验;最后,对面向单纤100 Tbit/s容量的光传输技术的研究前景进行了展望。     

Distributed optical control plane for dynamic lightpath establishment in translucent optical networks based on reachability graph

In transparent optical networks, physical layer impairments (PLIs) incurred by non-ideal optical transmission media accumulate along an optical path, and the overall effect determines the optical feasibility of the lightpaths. In addition, transparent optical networks suffer from inefficient wavelength utilization, as a connection request may be rejected because of non-availability of a common wavelength on all the links along the chosen route. To increase optical reach, resource utilization, and average call acceptance ratio (and hence revenues), network operators are resort to translucent optical networks. In these networks a limited number of regenerators are placed at a selected set of nodes. In this scenario development of an optical control plane which is aware of PLIs, location and number of regenerators, is of paramount importance for on-demand lightpath provisioning. In this paper, we propose a novel approach of constructing a reachability graph of the physical network considering PLIs and regenerators. If there is no transparent path in the physical network, we route the connections with multiple transparent segments on the reachability graph. We propose efficient mechanisms and corresponding GMPLS protocol extensions for impairment and regenerator aware routing and wavelength assignment (IRA-RWA) in translucent optical networks. The simulation results suggest that our proposed approach together with LSP stitching signaling mechanism is feasible to implement and close to deployment.     

EDFA和DCM在长途传输OLP系统中的应用

随着OLP在光通信网络的大量应用,将不可避免地对超长距离、超大容量传输系统干线也采取相应的保护措施,EDFA和DCM是目前广泛应用于解决超长距离、超大容量传输系统在OLP中存在问题的优选技术。以西武40Gbit/s波分干线为例,对EDFA和DCM在长途传输OLP系统中的应用提供一些参考。     

An optical packet switch based on WDM technologies

Dense wavelength-division multiplexing (DWDM) technology offers tremendous transmission capacity in optical fiber communications. However, switching and routing capacity lags behind the transmission capacity, since most of today's packet switches and routers are implemented using slower electronic components. Optical packet switches are one of the potential candidates to improve switching capacity to be comparable with optical transmission capacity. In this paper, we present an optically transparent asynchronous transfer mode (OPATM) switch that consists of a photonic front-end processor and a WDM switching fabric. A WDM loop memory is deployed as a multiported shared memory in the switching fabric. The photonic front-end processor performs the cell delineation, VPI/VCI overwriting, and cell synchronization functions in the optical domain under the control of electronic signals. The WDM switching fabric stores and forwards cells from each input port to one or more specific output ports determined by the electronic route controller. We have demonstrated with experiments the functions and capabilities of the front-end processor and the switching fabric at the header-processing rate of 2.5 Gb/s. Other than ATM, the switching architecture can be easily modified to apply to other types of fixed-length payload formats with different bit rates. Using this kind of photonic switch to route information, an optical network has the advantages of bit rate, wavelength, and signal-format transparencies. Within the transparency distance, the network is capable of handling a widely heterogeneous mix of traffic, including even analog signals.     

Provisioning Methods for Bit-Rate-Differentiated Services in Hybrid Optical Networks

This paper addresses the problem of routing and wavelength assignment of bit-rate-differentiated optical services in a hybrid network. Hybrid optical networks are composed of resources, such as fiber links and photonic/electronic switches, that vary in their capabilities and transmission qualities. These networks are also responsible for the realization of optical services with varying quality-of-service (QoS) guarantees. In such networks, it is required to have a cost-effective assignment of the optical and electronic resources to these services in order to maximize the revenue of the network operator. This paper deals with optical services that are defined according to their tolerance to transmission impairments. We first divide the provisioning problem into two phases: (1) routing and (2) wavelength assignment and regeneration reservation. In the routing phase, a set of k-routes are generated to select from in the second phase, where each route optimizes a specific aspect of the problem (e.g., number of hops, maximum accumulated noise, etc.). The second phase, using the information about the resources along each route, attempts at finding the best wavelength allocation on that route such that the signal quality meets the service-level agreement (SLA). The second phase also uses the minimum number of regenerator ports on intermediate nodes for the purpose of wavelength translation and signal clean-up. Comparisons of the above scheme with a probing-based method, reveal substantial enhancements to the blocking performance with a maximum running time increase of 60%. In addition, the use of multiple routes provides higher reduction in the blocking probability over single-routing schemes. Moreover, the proposed, non-pessimistic, provisioning approach has a major impact on reducing the regeneration budget of the network.     

一种用于混合通信网机会式路由选择算法

传统的路由协议都是针对特定的有线或无线网络,仅仅考虑路由的建立过程、路由建立过程中的收敛速度、路由维护的网络开销及路由动态更新时环路的避免等性能。将其用于有线无线混合传输网络会导致较低系统性能。机会式路由选择算法综合分析了无线链路状态和网络时延的影响,得出了各路径优先级的计算表达式,在路由选择时根据各条路径的优先级来选择路由。仿真结果表明,与传统路由算法相比较,该算法能够提高系统吞吐量和减少系统传输时延。