基于波长和模式混合复用的片上光交换网络架构

为有效地提高片上光交换网络的交换容量及规模,提出了一种基于波长和模式混合复用的无阻塞片上光交换网络架构。首先设计了基于微环谐振器的波长和模式混合复用的2×2光开关,并采用Benes拓扑互连成大规模无阻塞的交换网络。此外,通过设计波长和模式选择及复用模块,使所有节点间能够并行传输数据,并支持多播通信。为了验证所提观点,利用Ansys Lumerical仿真平台模拟了一个支持2种模式和4种波长混合复用的16×16光交换网络。仿真验证了所提交换网络能够实现所有节点间多维复用信号的并行数据交换,且16×16网络的最大插入损耗小于2.1 dB,模间串扰小于-18.4 dB,网络最大和最小插入损耗差值小于0.5 dB,证明该交换网络具有良好的公平性。最后将所提结构与传统的基于单波长单模式以及多波长单模式的光交换网络进行对比,证明了所提结构可以在不增加波长成本的情况下提升交换网络的容量及节点的规模。     

关联复杂网络建模及辨识研究

运用异质耦合拆分方法和驱动-响应模型,提出关联复杂网络节点参数和拓扑结构的辨识方法.首先,研究异质关联复杂网络建模方法,进而依据网络耦合性质不同,拆分构造了两类异质关联复杂网络.然后运用驱动-响应模型、LaSalle不变原理和Gram矩阵,设计节点系统参数和拓扑参数的自适应辨识观测器.所提的观测器能在线获取网络的节点参数、不同耦合性质的拓扑参数.最后,通过数值仿真验证所提方法的有效性.     

弹性光网络中基于效用的公平性感知动态频谱分配方案(英文)

针对弹性光网络中不同粒度业务之间的服务公平性问题,提出了公平性感知的动态频谱分配算法.通过引入一个新的效用函数,使得进行频谱分配时不仅考虑不同粒度业务间的服务公平性,而且还兼顾网络整体的频谱资源利用率,从而大大缓解了网络整体阻塞性能损伤.仿真结果表明,在动态网络环境下,该方案可以极大地提高弹性光网络中不同粒度业务之间的服务公平性,并且没有明显的阻塞性能恶化.     

基于预期流优化的空间网络引力模型

从优化预期流的角度提出了一个空间网络模型,其构建目标是使得整个网络的预期流总和最大化.通过改变表征网络对节点适应度和对地理因素依赖程度的两个参数α和γ的取值,网络的拓扑可从异质的星形类网络逐渐演变成同质的类似道路网的网络.利用所提出的引力模型仿真了中国城市航空网,并将其统计特征与实际网络进行了比较.最后,讨论了预期流和实际流（网络中实际的边权）之间的关系. 关键词： 空间网络 预期流 引力 中国城市航空网     

波群模型和支持流量疏导的光交换结构

针对多粒度应用,开发了一种用于流量疏导的波群模型,并引入一种基于此模型的新型智能交换结构.该光交换结构提供了独特的区分粒度到相应隧道进行有效处理的方法.此外,还讨论了控制层粒度分离时采用的两个关键的动态算法模块.仿真结果显示这种特殊的通道分离方法有效提高了处理动态连接请求时每个光路径的平均信号通道质量和阻塞性能.     

基于感知流量算法的复杂网络拥塞问题研究

研究了在具有感知流量的路由策略下,复杂网络的拓扑结构对网络中传输流量的影响.为了描述数据包传输过程的有效性,通过引入一个状态参数,利用由稳态到拥塞的指标流量相变值来刻画网络的吞吐量.基于每个节点的数据包处理能力与该节点的度或介数成比例提出两种模型并进行仿真.仿真结果表明,平均度相同的情况下,模型Ⅰ中,WS小世界网络比ER随机网络和BA无标度网络更容易产生拥塞;模型Ⅱ中,所有网络容量都得到较大的提高,尤其是WS小世界网络.但当网络的基本连接参数改变时,哪种模型更利于网络的流量传输,还要依据网络本身的结构特性 关键词： 复杂网络 无标度网络 感知流量 拥塞     

一类输出耦合时延复杂动态网络故障诊断研究

文章针对一类输出耦合时延复杂动态网络模型,考虑节点动力学参数未知的情况,基于网络外部同步思想,提出一种对该类复杂动态网络进行故障诊断的方法.利用节点的输出变量作为反馈变量设计控制器,根据Lyapunov稳定性理论,推导网络达到外部同步的条件.该方法可以实时监控时延网络拓扑结构的变化情况,对网络进行故障诊断.通过仿真验证本文方法的有效性. 关键词： 复杂动态网络 时延 故障诊断 节点参数     

分布式控制光网络的一种高效信令协议

为了在光网络中建立连接,信令协议需要依次配置路径沿途节点上的光交叉矩阵完成.提出了一种高效的信令协议,使各节点的光交叉矩阵的切换过程并行完成,可在光网络中实现快速光路供给.在分布式离散时间仿真平台上所做出的深入仿真结果表明此信令协议能够获得比反向预留信令协议更好的网络性能,可获得更低的阻塞概率、更短的平均连接时间和最长连接时间,尽管可能付出了稍高一些的控制带宽的代价.     

适用于多粒度光网络的共享保护算法及其分析

结合多粒度光网络自身特点提出了两种适用于多粒度光网络中的共享保护算法,它们分别基于波带粒度和基于波长粒度对光层连接提供保护.仿真结果显示,提出的算法性能优于以往的专用保护算法,通过对仿真结果的分析,得出了网络参量变化对各个算法的影响.     

智能光网络中一种新型的分布式恢复方法

提出了一种基于固定备用路由和目的端触发的智能光网络中的分布式恢复方法,所选择的任一对源端节点和目的的端节点之间的固定备用路由包括该节点对之间的k条最短路径路由和基于部分链路无关的路由.目的端节点一旦探测到业务通道的失效将立即启动恢复进程,根据网络当前的资源使用情况,在这些备用路由中按照一定的次序选择一条恢复路由并为此分配一条可用的波长(对于没有波长变换器的光网络),然后将恢复通道的建立请求消息发送给该恢复通道的相关节点,这些相关节点可以锁定相关的网络资源,以避免来自其他恢复通道的竞争.所提出的算法增加了固定备用路由的数量,从仿真结果可以看出,该方法明显改善了失效连接的阻塞性能.     

The Effects of Polarization and Non-Linearity on the Performance of WDM System with Optical Cross-Connects

The performance of a wavelength division multiplexing (WDM) system with optical cross-connects (OXCs) and in the presence of polarization and nonlinear effects was analyzed. We determined the effect of PMD and PDL; nonlinearity such as XPM, SPM, and FWM; and CD on the system performance. We found that the system outage probability is highest at DGD threshold for the respective maximum eye closure (EC). We showed that the allowable DGD depends on the time slot for one bit T, which is the inverse of the network bit rate. Wider T is more immune to large PMD with the EC still maintained at the same level since DGD/T is unchanged. Our analysis also indicated that as DGD increases, BER increases. The BER also increases with increase in PDL and further increases with the presence of XPM, SPM, FWM, and CD.     

Reflections from polished single mode fiber ends

Abstract

The performance of a wavelength division multiplexing (WDM) system with optical cross-connects (OXCs) and in the presence of polarization and nonlinear effects was analyzed. We determined the effect of PMD and PDL; nonlinearity such as XPM, SPM, and FWM; and CD on the system performance. We found that the system outage probability is highest at DGD threshold for the respective maximum eye closure (EC). We showed that the allowable DGD depends on the time slot for one bit T, which is the inverse of the network bit rate. Wider T is more immune to large PMD with the EC still maintained at the same level since DGD/T is unchanged. Our analysis also indicated that as DGD increases, BER increases. The BER also increases with increase in PDL and further increases with the presence of XPM, SPM, FWM, and CD.     

Performance analysis of topologies for optical wavelength convertible networks

An architecture of wavelength converters shared per-node wavelength cross-connects is proposed to function the optical node in simulation. And first-fit wavelength allocation algorithm and Dijkstra shortest path routing algorithm are used. It is shown that star topology performs the best on blocking probability, average hop count and average packet delay, but it is unfavorable on link utilization. Furthermore, wavelength conversion is not ideal for the star topology. However, the ring topology network is the cost-optimal one if the appropriate wavelength conversion capability in network is to be considered.     

适用于多粒度光网络的共享保护算法及其分析

结合多粒度光网络自身特点提出了两种适用于多粒度光网络中的共享保护算法,它们分别基于波带粒度和基于波长粒度对光层连接提供保护.仿真结果显示,提出的算法性能优于以往的专用保护算法,通过对仿真结果的分析,得出了网络参量变化对各个算法的影响.     

多波长光交叉连接节点中的串扰研究

密集波分复用技术(DWDM)在提供传输能力的同时,还具有无可比拟的联网优势.光交叉连接(OXC)是其中的关键技术.由于OXC可对光波长进行全光的交叉连接,极大的提高了系统的容量.但由于在光链路上没有电的再生,使得噪音在光信道上积累起来,尤其是引入无法消除的同频串扰对系统造成了严重的影响.本文从全光通信网络(AON)的几种节点结构出发,讨论了信道的串扰机制,并对如何优化OXC节点结构进行了研究.     

Blocking probability analysis model for flexible spectrum optical networks

Compared to the traditional wavelength division multiplexing （WDM） optical networks with rigid and coarse granularities, flexible spectrum optical networks have high spectrum efficiency, which can support the service with various bandwidth requirements, such as sub and super channel. Among all network performance parameters, blocking probability is an important parameter for the performance evaluation and network planning in circuit~based optical networks including flexible spectrum optical networks. We propose an analytical method of blocking probability computation for flexible spectrum optical networks in this letter through mathematical analysis and theoretical derivation. Two blocking probability models are built respectively based on whether considering spectrum consecutiveness or not. Numerical results validate our proposed blocking probability models under different link capacity and traffic loads.     

Blocking probability analysis of survivable routing in WDM optical networks with/without sparse-wavelength conversion

In this paper, a new algorithm for wavelength assignment has been proposed and its performance is evaluated in terms of blocking probability and fairness. It has been shown that the proposed algorithm offers the least blocking probability. The blocking performance of wavelength division multiplexing (WDM) network has been analyzed for the network having 10 nodes and for varying loads. As the load per link (in Erlangs) increases, the blocking probability increases. The result shows that the performance of first-fit algorithm is better than random algorithm whereas the proposed algorithm offers the least blocking.     

Performance enhancement of optical burst switched networks

Optical burst switching (OBS) is an optical switching paradigm which offers a good tradeoff between the traditional optical circuit switching (OCS) and optical packet switching (OPS) since it has the relatively easy implementation of the first and the efficient bandwidth utilization of the second. Hence, OBS is a promising technology for the next generation optical Internet. A buffer-less OBS network can be implemented using ordinary optical communication equipment without the need for either wavelength converters or optical memories. In an OBS network, burst-loss performance is a critical concern. In OBS, the data-burst transmission is delayed by an offset time (relative to its burst control packet (BCP), or header) and the burst follows its header without waiting for an acknowledgment for resource reservation. Thus, a burst may be lost at an intermediate node due to contention, which is generally resolved according to the local routing and bandwidth information. The routing table maintained in each OBS node is generally pre-computed and fixed to forward the data bursts. Such a static forwarding feature might have limited efficiency to resolve contentions. Moreover, a burst may be lost and the network may be congested when a network element (e.g., fiber link) fails. In this paper, an efficient integrated scheme based on dynamic routing and burst segmentation has been proposed to improve reliability of data transport and network load balancing in optical burst switched networks. Simulation results demonstrate that the proposed approach reduces effectively blocking probability and hence contention. Further, it provides end-to-end throughput performance also. Hence, it establishes an appropriate tradeoff between loss rate and end-to-end throughput.