基于组播树的多粒度波带静态疏导算法

研究了波带交换中的静态业务疏导算法。波带交换可以有效地减少波长交换的端口数量,但是当波带粒度值取固定值时,波带的粒度难以取得合适值。波带的粒度大,有助于减少交换端口的数量,但是波带利用率低;波带粒度小,有助于提高波带利用率,但是交换端口的数量多。为此,提出了多粒度的波带取值方法。根据静态业务疏导与组播路由的相似性,提出了利用构造组播树解决静态疏导问题的方法。另外,为了减少波带与波长交换平面互联的端口数量,采用了同目的地的波带疏导策略,并针对这一疏导策略提出了一种新的波带疏导辅助图。仿真结果表明,相对于固定粒度的波带取值,可以有效地减少交换端口的数量,并提高波带利用率。     

A new multi-granularity traffic grooming routing algorithm in IP over WDM networks

In IP over WDM networks, since there is a large bandwidth gap between a wavelength capacity and the actual bandwidth required by each user, it is necessary to multiplex low-rate traffic streams (LRSs) into lightpaths by traffic grooming. However, with the number of wavelengths increases, a large number of all optical (OOO) transmitting ports are consumed. Meanwhile, the multi-hop grooming with incorporating full-wavelength conversion capacity in each node requires too many optical-electrical-optical (OEO) ports inevitably. To solve theses problems, waveband switching and intra-band wavelength conversion are proposed. By integrating traffic grooming and waveband switching, this paper devises a new multi-granularity traffic grooming mechanism with the function of intra-band wavelength conversion. Based on the proposed mechanism and integrated grooming policy (IGP), a new heuristic routing algorithm called multi-granularity traffic grooming based on integrated auxiliary graph (MGIAG) is also proposed since the traffic grooming problem is NP-hard. Simulation results show that, compared to traditional integrated grooming algorithm (IGA), MGIAG can save more ports and obtain lower blocking probability. Compared to traditional single-hop traffic grooming algorithm (SHA), lower blocking probability and more savings in transmitting ports can be achieved by multi-hop grooming in MGIAG and IGA although they consume more OEO ports.     

Performance analysis of dedicated protection and shared protection for waveband switching based on multi-granularity optical cross-connect

In order to save the switching ports and the cost of Multi-Granularity Optical Cross-Connect (MG-OXC), the waveband switching technique was proposed to groom multiple wavelength-level traffic to a few waveband tunnels to be switched by a few switching ports in MG-OXC. At the same time, protection for fibers is very important to ensure the service continuity since each wavelength carries a lot of traffic. Although existing works have addressed the waveband switching protection, most of them separately considered only the dedicated protection or shared protection in static demand scenario and did not deeply analyze and compare the dedicated protection and shared protection in dynamic demand scenario. Therefore, in this paper, we deeply study the consumptions of wavelengths in fibers and ports in MG-OXCs for Waveband Shared Protection (WSP) and Waveband Dedicated Protection (WDP) in dynamic demand scenario, and propose the port-cost calculation and update methods based on a new waveband layered auxiliary graph that is developed based on MG-OXC structure. In simulations, we compare WSP, WDP, traditional end-to-end waveband shared protection and traditional end-to-end waveband dedicated protection. Simulation results show that the shared protection has smaller port-cost, better wavelength utilization efficiency and lower blocking probability than the dedicated protection with the same waveband switching policy, and the sub-path waveband switching has bigger port-cost, better wavelength utilization efficiency and lower blocking probability than the end-to-end waveband switching with the same backup wavelength assignment policy.     

光交叉连接节点的功能结构

光交叉连接(OXC)是未来波分复用光传送网实现交换与选路功能的核心部件.目前,OXC节点的物理结构得到深入研究,已经提出了一些采用不同光子器件的OXC实现方案.本文从描述光交叉连接功能的角度出发,给出一种分析OXC节点功能结构的模型,并比较各种OXC方案在功能结构上的差异。     

基于节能的绿色光网络路由算法的研究

在传统的网络路由算法中,一般采用最短路径算法进行路由选路,最短路径算法以节点间的距离为权重,计算一条由源节点至目的节点的权重最小的路径以完成路由。最短路径算法虽然最小化了距离长度代价,却没有考虑能耗问题,所以使用最短路径算法所得出路径的能耗并不一定是最小的。针对这一问题,提出一种新型的综合性绿色路由算法,设定能耗作为节点间的权重,融合光旁路及业务量疏导,同时考虑路由和波长分配(RWA)问题,将完成每个业务所需要的能耗最小化,实现节能。仿真结果表明,与最短路径算法相比,绿色路由算法在较大规模网络中能够节省约40%的能耗,节能效果相当显著。     

串扰对密集波分复用网络扩展性的影响

串扰是限制密集波分复用网络扩展的一个重要因素。理论分析了三种典型光交叉连接中的串扰。结果表明基于扩展贝奈斯光交换结构的光交叉连接可以完全消除低于二阶的各类串扰,同时,若将可调谐的窄带滤波器引入到结构2中可以消除低于三阶的各类串扰。用数值模拟的方法分析了带内串扰对强度调制直接检测网络扩展性的影响。结果表明,基于扩展贝奈斯光交换结构的光交叉连接对器件串扰系数的要求得到了很大的放宽,用它来组建的密集波分复用网络具有很好的扩展性。串扰多是由构成光交换节点中各种器件的非理想性造成的,通过分析得出器件中产生的串扰可以从系统中得到很好的解决。     

Routing protocol for wireless quantum multi-hop mesh backbone network based on partially entangled GHZ state

Quantum multi-hop teleportation is important in the field of quantum communication. In this study, we propose a quantum multi-hop communication model and a quantum routing protocol with multihop teleportation for wireless mesh backbone networks. Based on an analysis of quantum multi-hop protocols, a partially entangled Greenberger–Horne–Zeilinger (GHZ) state is selected as the quantum channel for the proposed protocol. Both quantum and classical wireless channels exist between two neighboring nodes along the route. With the proposed routing protocol, quantum information can be transmitted hop by hop from the source node to the destination node. Based on multi-hop teleportation based on the partially entangled GHZ state, a quantum route established with the minimum number of hops. The difference between our routing protocol and the classical one is that in the former, the processes used to find a quantum route and establish quantum channel entanglement occur simultaneously. The Bell state measurement results of each hop are piggybacked to quantum route finding information. This method reduces the total number of packets and the magnitude of air interface delay. The deduction of the establishment of a quantum channel between source and destination is also presented here. The final success probability of quantum multi-hop teleportation in wireless mesh backbone networks was simulated and analyzed. Our research shows that quantum multi-hop teleportation in wireless mesh backbone networks through a partially entangled GHZ state is feasible.     

A Bidirectional “Y” Type OXC Structure Using the Least Optical Switches

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Green and double-win planning for IP over WDM optical networks

Saving the electrical requirements of network operators around the world makes power costs show a continuously decreasing trend. However, reducing the power costs is not only one way of gaining the marginal profit, a network operator also needs providing high-level quality of service (QoS), as well as employs effective strategies of pricing and hybrid grooming (i.e., integration of traffic grooming with an optical bypass) to make more users wish to pay the expense for their applications. In the final, users enjoy their services meanwhile operators obtain high profit in a power-efficient way, i.e., “double-win”. Accordingly, we propose the fast sub-optimal heuristics including Single-hop and Power-efficient Grooming algorithm based on Game theory (SPG2) as well as Multi-hop and Power-efficient Grooming algorithm based on Game theory (MPG2). Simulation results demonstrate that, compared with SPG2, MPG2 has the better comprehensive performance of both power efficiency and double-win between user and network operator in IP over WDM networks.     

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.     

Impairment-aware QoS provisioning in dual-header OBS networks

Signal degradation due to physical impairments may result in unacceptable bit-error rates of received signals at the destination. Based on earlier work, we study the impairment-aware quality of service (QoS) provisioning problem in dual-header optical burst switching (OBS) networks that employ two control packets for each data burst. At an OBS node, the proposed algorithm schedule bursts for transmission by searching for available resources using admission control and preemption. The algorithm also verifies signal quality. Simulation results show that this algorithm is effective in providing QoS support in OBS networks while considering physical impairment effects.     

GMPLS: IP-Centric Control Protocols for Optical Networks(Tutorial)

Recent advances in optical networking technologies, particularly DWDM and MEMS, promise the transmission and switching of huge bandwidth capacity. The carriers have convinced of that their revenue must be earned from efficient bandwidth management instead of unsophisticated increase in capacity. The distributed control plane can offer more flexibility, reliability and scalability, whose functions include addressing, resource and topology discovery, route computation, provisioning and restoration. Generalized Multi-Protocol Label Switching (GMPLS), an IP-centric control plane, inherit the best features of IP and ATM technologies in terms of QoS and traffic engineering. Besides,GMPLS introduces enhancements to the existing IP routing and signaling protocols by supporting not only packet switching networks (IP) and frame/cell switching networks (ATM), but also networks that perform switching in time (e.g. SDH/SONET, PDH, G.709), wavelength (lambdas), and space (fiber) domain.     

Migration of broadcast-and-select optical crossconnects from semi-static to dynamic reconfiguration and their physical layer modeling

Optical Crossconnects (OXC) are indispensable for the proliferation of broadband services. Next generation OXCs should be dynamically reconfigurable, to render the optical layer flexible and agile, cost competitive, in order to be a viable alternative to fully electronic solutions and multi-service, i.e. to be able to handle both optical circuits and packets equally well. In this work, an evolutionary migration scenario from semi-static to dynamically reconfigurable broadcast-and-select OXCs is presented. The cornerstone of this approach is modularity in both the node architecture and the corresponding functionality, since these two are inextricably linked. Here, the three evolutionary steps of a modular broadcast-and-select architecture are presented, their principle of operation is explained and their complexity is analyzed. The key building-blocks to implement these OXCs are optical switching elements operating in a gated mode and tunable wavelength converters. Concerning the physical performance of these architectures, an important consideration is that node capacity is traded for higher node cascadeability. This trade-off is studied extensively considering a combination of different switching technologies and optical components. Moreover, the 2R regenerative properties of the all-optical and optoelectronic wavelength converters play a key role in the node cascadeability assessment which is otherwise compromised by OSNR limitations. For this reason, analytical models providing an insight on how certain physical mechanisms are leading to performance degradation are used. The final assessment is made using a commercial simulation tool, allowing the derivation of conclusions for the size of the transparent islands.     

分布式光网络中的波长和端口数目优化分析

研究了分布式Mesh光网络中动态业务疏导问题中的波长和端口优化问题,通过对分布式Mesh光网络中不同业务和网络拓扑情况下的网络结点波长和端口使用数目的仿真分析,得出网络中的合理波长和端口数目配置,为网络规划和设计提供依据.     

OADM的设计

OADM节点是WDM光网络的关键节点之一。研究了OADM节点的实现方法,提出了一种设计方案,并讨论了光上下路开关阵列的驱动和监控的软硬件制作,完成了下路光功率监测的电路设计以及软件设计。分析了OADM节点保护倒换的原理和节点中的串扰问题。     

WDM网状网中动态域间流量疏导策略

对波分复用(Wavelength Division Multiplexing,WDM)网状网中的动态域间流量疏导问题进行了深入研究.在源路由模式下,提出了一种基于固定备选路由方式的动态域间流量疏导算法,并在其基础上提出了只考虑波长均衡和同时考虑波长均衡与业务均衡的改进方法.该算法可以有效地避免路由环,得到较低的阻塞率,节省全网的收发器数目和波长资源.仿真结果表明,这种算法可以有效地改善网络性能.     

一种带物理约束的光网络业务量疏导方法

提出了基于最大收益的捆绑疏导算法(MRA)来解决光网络中具有多种物理约束的业务量疏导问题。MRA首先在物理拓扑上逐个放置业务, 随后捆绑细粒度业务、实现管道实例化。即考虑业务的路由情况, 将其在物理拓扑上的路由都视为单跳的细粒度管道, 然后使用基于深度优先搜索的方法来检查哪些业务能够捆绑到一起形成多跳粗粒度的潜在管道, 以节省中间节点的细粒度交换容量。再从这些粗粒度的潜在管道中, 使用最大收益的方法遴选出具有最大成本收益的无冲突集合, 并加以实例化。仿真结果显示, 在处理多个物理约束时, MRA在容量和实现成本上均优于现有的算法, 并且它能处理多达百个节点以上的大网络中的业务量疏导问题。     

一种新的光突发交换网络信令协议与分析

提出了一种新的光突发交换网络信令协议,即DSH区分服务混合信令.根据实时（电路仿真）业务和非实时（数据）业务对QoS的不同要求分别采用TAW和JET信令控制协议,尤其是对TAW信令做了相应改进,使之更适合于OBS网络承载电路仿真业务.利用电路仿真业务发出的呼叫请求,在端到端的波长通道中建立虚通路,并在整个呼叫持续过程中保持虚通路的连接,这样可以保证电路仿真业务的端到端时延最小并避免信息丢失.通过理论分析和系统仿真,研究了DSH混合信令的性能及其对波长利用率和实时业务呼损率的影响.     

Switching dynamics and modeling of multi-domain Zr-Doped HfO2 ferroelectric thin films

HfO₂-based ferroelectrics have attracted attention as promising materials for advanced memory applications owing to their negative capacitance effect, high scalability, and full-CMOS compatibility. Accordingly, the switching dynamics of HfO₂ thin films have been actively discussed and simulated using the Landau-Khalatnikov equation (LK model). Although the simulated results agree with experimental results in many studies, there is a slight dissimilarity near the coercive field in the polarization-electric field curve. For accurate and general modeling, a new model that combines the conventional LK model and Euler's equation was proposed in this work. The model was examined under single-domain and multi-domain conditions. The simulated curves using the Landau-Euler method better fit with measured curves than those using the LK model.     

SOA-assisted Sagnac switch and investigation of its roadmap from 10 to 40 GHz

Future broadband optical communications networks will rely on all-optical switches to perform a set of processing functions exclusively in the optical domain. Interferometric optical switches using semiconductor optical amplifier (SOA) nonlinearities can perform efficient optical switching with few tens of fJ control energies and short fiber lengths allowing for monolithic integration. In this paper we present work performed with a three terminal SOA-assisted Sagnac interferometer. We review all-optical Boolean AND and XOR logic results at 10 GHz and 10 Gb/s for full duty cycle and pseudo-random data pattern operation, respectively, achieved with adequate contrast ratios, remarkably low switching energies and low pattern dependence. The ability of the device to be cascaded was proved up to 10 GHz by recirculating stably for hours arbitrary pattern profiles. Finally, and in view of the extension of photonic networks single channel data rates beyond 40 Gb/s, the performance of the switch was simulated in terms of its critical parameters. The obtained results showed that full switching operation at 40 GHz or higher is feasible either by deploying gain recovery reduction techniques in bulk and quantum well SOAs or alternatively other technologically advanced optical devices, such as quantum dot SOAs.