知识窗

波带交换波带交换(WBS)是将多个波长组合在一起作为整体进行交换,由于在光交叉连接(OXC)中只使用一个端口,可减少端口数,降低成本。在波长路由网络中,OXC通常是单一粒度,仅在波长级进行交换,每个波长需要一个端口。波带交换网络则使用多粒度OXC(MG-OXC),可对波长、波带以至光纤进行交换和分插。MG-OXC包含波长交叉连接(WXC)、波带交叉连接(BXC)和光纤交叉连接(FXC)。按照交换结构的不同,可有多层结构的MG-OXC和单层结构的MG-OXC,前者的光交换结构包含独立的WXC、BXC和FXC3个部分,后者则具有一个公共的光交换结构。单层…     

光网络中的波带交换技术

波分复用光网络已成为广域骨干网最可行的体系解决方案.波带交换(WBS)因其能减小光交叉连接器的端口数、控制复杂性和连接费用等,引起了广泛的关注.文章指出了WBS和传统波长路由的不同之处,对WBS的两种多粒度光交叉连接器结构进行了分析.文中还提出了基于WBS的各种方案和光路成组策略,讨论了WBS网络中的波带转换和故障恢复问题.     

支持OTDM的多粒度光交换结构研究

多粒度光交换能减小光交叉连接矩阵的规模,降低光节点的成本,然而现有多粒度光交换结构的最小交换粒度常为波长,该交换粒度太大,会导致核心节点的链路利用率低.文章在多层MG-OXC基础上,提出了一种新型多粒度交换结构,实现了波带交换和OTDM的结合.该新型MG-OXC结构端口较少,并且可以提高传输速率,同时也因此降低了同等信息量下波长的使用教量,为网络提供了更大的传输容量,能够很好地适应光网络发展的需要.     

智能多粒度光交叉连接节点的设计与实现

提出了一种新型多粒度光交叉连接(MG-OXC)的体系结构,它可以完成光纤、波带、波长的交换,以及不同粒度业务的上下话路.同时介绍了由三个真实多粒度光交叉连接节点与若干虚拟光节点所组成的智能多粒度光网络试验平台的设计与实现.实验平台支持动态的可配置的网络拓扑、自动的邻居发现、受限的波长、波带路由,以及光层快速的保护与恢复.     

支持OTDM的多粒度光交换结构研究

多粒度光交换能减小光交叉连接矩阵的规模,降低光节点的成本,然而现有多粒度光交换结构的最小交换粒度常为波长,该交换粒度太大,会导致核心节点的链路利用率低。在多层MG-OXC基础上,提出了一种新型多粒度交换结构,实现了波带交换和OTDM的结合。该新型MG-OXC结构端口较少,并且可以提高传输速率,同时也因此降低了同等信息量下波长的使用数量,为网络提供了更大的传输容量,能够很好地适应光网络发展的需要。     

动态业务条件多颗粒度交换光网络性能研究

本文研究了动态业务条件下基于波带、波长两级交换的多颗粒度光交叉连接节点(MG-OXC)的优化设计,并提出了一种适用于多颗粒度交换光网络(MG-ON)的动态路由、波长分配和业务分组(Traffic Grouping)算法.利用实际网络拓扑对上述MG-ON方案进行了数值仿真实验,比较研究了MG-ON与传统OXC节点构成的波长路由光网络(WRON)的动态业务阻塞率性能,结果表明MG-ON的网络性能可以满足动态业务的要求.     

业务疏导技术在WDM网络及OPS网络中的应用

在波分复用(WDM)光网络中,可使用业务疏导(Traffic Grooming)技术来提高网络性能,降低网络成本.详细阐述了WDM光网络中业务疏导的基本概念及主要目标,并对国内外研究现状进行了总结.最后介绍了OPS光交换网络中使用的业务疏导技术.     

波带交换

波带交换(WBS)是将多个波长组合在一起作为整体进行交换，由于在光交叉连接(OXC)中只使用一个端口，可减少端口数，降低成本。     

一体化OADM/OXC节点降低串扰结构研究

提出并分析了一体化光分插复用 /光交叉连接 (OADM/OXC)的降低串扰节点结构。在波分复用 (WDM )光传送网络中 ,一体化节点可以同时完成对光通道的上下路与交叉连接功能。与传统结构节点相比 ,该结构中使用一组 1× 2和 2× 1光开关与小规模的光交叉连接阵列实现光通道的上下路与交叉连接。仿真结果证明 ,该结构中由于同频串扰造成的功率代价显著下降。     

IP over WDM光网络技术及其实现方案

从光传送网的发展趋势出发,分析了IP over WDM光网络的网络结构和协议规范.讨论了IP over WDM光网络的相关技术,并对分组交换技术进行了较为系统的介绍,最后,为了实现IP over WDM光网络,提出了6MPLS T-MPLS和GMPLS ASON的解决方案.     

Waveband Switching for Dynamic Traffic Demands in Multigranular Optical Networks

Waveband switching (WBS) in conjunction with multigranular optical cross-connect (MG-OXC) architectures can reduce the cost and complexity of OXCs. In this paper, we study the performance of different MG-OXC architectures under dynamic traffic. In the case with online incremental traffic, we compare two MG-OXC architectures in terms of the blocking probability of new lightpath requests and study the impact of port counts and traffic loads. We develop an online integer linear programming model (On-ILP), which minimizes the number of used ports and the request blocking probability, given a fixed number of wavelengths and MG-OXC architecture. The On-ILP optimizes the routing of new lightpaths so as to maximize lightpath grouping and reduce the port count given that existing traffic cannot be rearranged. We also propose a new efficient heuristic algorithm, called maximum overlap ratio (MOR) to satisfy incremental traffic and compare it with the On-ILP, first-fit, and random-fit algorithms. Our results and analysis indicate that using WBS with MG-OXCs can reduce the size (and, hence, the cost) of switching fabrics compared to using ordinary OXCs. Based on the results and observations in the incremental traffic case, we further study the performance of a particular MG-OXC architecture under fully dynamic or fluctuating traffic. Our simulations show that the proposed heuristic algorithm waveband assignment with path graph, which groups wavelengths to bands and uses wavelength converters efficiently under fluctuating traffic, significantly outperforms other heuristic algorithms.     

On service provisioning using light-trails in WDM optical networks with waveband switching

As the number of wavelengths in a single optical fiber increases, so does the number of ports needed for wavelength switching in optical cross-connects (OXCs), which may significantly increase the cost and difficulty associated with controlling large OXCs. Waveband switching (WBS) treats several wavelengths as a bundle that is switched through a single port if they share the same switch route, so that the number of ports needed can be reduced. On the other hand, light-trails in wavelength division multiplexing (WDM) optical networks allow intermediate nodes on established optical paths to access the data paths whereas light-paths only allow two end nodes to access the data paths. Therefore, light-trails offer significantly better flexibility for service provisioning and traffic grooming. In this article, we study service provisioning using light-trails in WDM optical networks with the WBS capability under a static traffic model. For comparison, integer linear programs are formulated for establishing light-trails with and without WBS. Numerical studies show that in certain cases, service provisioning with WBS in light-trail networks can reduce the number of ports needed while providing a more flexible sub-wavelength service provisioning capability. However, contrary to intuition, in most cases applying the WBS technique requires more ports in OXCs in light-trail networks. This study provides insights into the network design problem that applies the WBS technology to light-trail based optical networks.     

Dynamic Waveband Switching in WDM Mesh Networks Based on a Generic Auxiliary Graph Model

Waveband switching (WBS) is a promising technique to reduce the switching and transmission costs in the optical domain of a wavelength-division multiplexing (WDM) network. This paper considers the problem of provisioning dynamic traffic using WBS in a WDM mesh network. The network of interest is a homogeneous WBS network, where each node has the functionality of WBS. The problem is called the dynamic WBS problem, which involves searching waveband-routes or wavelength-routes for the dynamically arriving traffic requests. The objective is to minimize the total switching and transmission costs in the optical domain. To solve the dynamic WBS problem, an auxiliary graph model capturing the network state is proposed. Based on the auxiliary graph, two heuristic on-line WBS algorithms with different waveband grouping policies are proposed, namely the wavelength-first WBS algorithm based on the auxiliary graph (WFAUG) and the waveband-first WBS algorithm based on the auxiliary graph (BFAUG). Simulation results indicate that WBS is an attractive technique which reduces the overall switching and transmission costs by up to 30% in the network. The results also show that the WFAUG algorithm outperforms the BFAUG algorithm in terms of port savings and cost savings.     

Uniform waveband assignment in optical mesh networks

The cost of an optical network in wavelength division multiplexing (WDM) networks can be reduced using optical reconfigurable optical add/drop multiplexers (ROADMs), which allow traffic to pass through without the need for an expensive optical-electro-optical (O-E-O) conversion. Waveband switching (WBS) is another technique to reduce the network cost by grouping consecutive wavelengths and switching them together using a single port per waveband. WBS has attracted the attention of researchers for its efficiency in reducing switching complexity and therefore cost in WDM optical networks. In this paper, we consider the problem of switching wavelengths as non-overlapping uniform wavebands, per link, for mesh networks using the minimum number of wavebands. Given a fixed band size b _s , we give integer linear programming formulations and present a heuristic solution to minimize the number of ROADMs (number of wavebands) in mesh networks that support a given traffic pattern. We show that the number of ROADMs (or number of ports in band-switching cross-connects) can be reduced significantly in mesh networks with WBS compared to wavelength switching using either the ILP or the heuristic algorithm. We also examine the performance of our band assignment algorithms under dynamic traffic.     

一种改进的多粒度光交叉连接结构

多粒度光交叉连接能够提供光纤、波带和波长三种粒度的光交换,这一机制能有效提高交换性能,同时通过交换端口数的减少来降低光交换的成本。在这种交换结构中,需要在下层进行交换的信号需要首先经过上层的交换,或者所有信号都需要被不加区分地解复用出来进行交换,这造成了信号的过大损耗和失真,以及交换端口的浪费。我们在介绍了现有的研究以后,提出一种改进后的多粒度光交叉连接结构。通过仿真分析,可以看出这一新结构能够比其他结构更灵活地配置交换端口,同时能够避免不必要的信号损耗和失真,降低交换成本。     

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.     

Performance analysis of an optical network employing waveband and traffic grooming

This paper analyses an optical network architecture composed by an arrangement of nodes equipped with multi-granular optical cross-connects (MG-OXCs) in addition to the usual optical cross-connects (OXCs). Then, selected network nodes can perform both waveband as well as traffic grooming operations and our goal is to assess the improvement on network performance brought by these additional capabilities. Specifically, the influence of the MG-OXC multi-granularity on the blocking probability is evaluated for 16 classes of service over a network based on the NSFNet topology. A mechanism of fairness in bandwidth capacity is also added to the connection admission control to manage the blocking probabilities of all kind of bandwidth requirements. Comprehensive computational simulation are carried out to compare eight distinct node architectures, showing that an adequate combination of waveband and single-wavelength ports of the MG-OXCs and OXCs allow a more efficient operation of a WDM optical network carrying multi-rate traffic.     

WDM智能光网络与IP业务

详细分析了 ＷＤＭ光网络的结构以及联网技术的演进过程，对如何压扁网络层次，实现ＩＰ直接ｏｖｅｒ ＷＤＭ，发挥 ＷＤＭ光传送网的巨大带宽优势进行了研究，提出 ＭＰＬＳ是当前解决 ＩＰ层与光层的融合以及跨层管理问题的关键技术。