Passband-width broadening design for WDM filter with lattice-forminterleave filter and arrayed-waveguide gratings

We successfully fabricated a high channel count and flat-top wavelength-division-multiplexing filter by integrating a waveguide-type interleave filter and two arrayed-waveguide grating on one chip. Optimizing the loss ripple of the interleave filter, we realized a 50-GHz spacing, 102-channel ports, a 1-dB passband of 30 GHz, and an insertion loss of 4 dB     

Arrayed waveguide gratings for wavelength routing

Wavelength routing can be performed in the optical domain for both long-haul and passive optical networks. Arrayed waveguide gratings (AWGs) can perform wavelength routing for a large number of optical channels and provide a high level of functionality on an integrated chip. The AWG guides light on a planar lightwave circuit into an array of waveguides that provide dispersion to separate the different wavelengths of light. Routing functions can be performed on individual wavelengths. With this technology, optical cross-connects, optical add/drop multiplexers, and passive optical routers have been demonstrated. Performance issues-such as insertion loss, polarization dependence, passband shape, passband position, crosstalk, and temperature dependence-are being addressed so that AWGs will be practical for deployment into systems     

策略路由在高校中的应用

1.概述目前高校网络应用都比较复杂,普遍采用多网络出口方式。其中一个出口为国家教育网出口,另一个通常为电信出口。ChinaNET通常是包月形式,无论学校使用的流量有多大,每月固定收取一定费用,但是由于通过ChinaNET访问CERNET资源的速度比较慢,而且教育网中有些资源是对ChinaNET屏蔽     

Distributed dynamic routing schemes

Schemes that do not explicitly use much information about the state of networks are briefly surveyed, with the focus on dynamic alternative routing (DAR), a simple but highly effective routing method currently planned for the British Telecom Network. State-dependent routing and how some of the methodology also has bearing on the control issue are discussed. The problem of dimensioning a network that uses dynamic routing (i.e. how much capacity is needed and where it should be put to provide an acceptable performance) is addressed. A practical example, which refers to routing in an international access network, is discussed. Some conclusions are drawn on the benefits and drawbacks of distributed routing     

周期性动态热效应光栅的研究

为使激光诱导动态光栅产生在空间上可分辨的高效率衍射光，光栅介质必须足够薄以满足光栅条件，但动态光栅自衍射效率却又随介质厚度的增加而增加，我们提出用相位匹配的周期性薄光栅组可解决这一矛盾，并在实验上用周期性热效应光栅对理论进行了验证。     

应用单纯形算法解决动态路由问题

探讨了如何在长途电话交换网中应用单纯形算法解决动态路由问题，并介绍了算法运行情况和运行结果。单纯形算法能够在很短的时间内得到质量很好的全局优化的路由方案。     

Optimal dynamic routing in double ring networks

The dynamic routing problem with multiple destinations on ring networks is examined. The authors discuss the peculiarities of the ring topology as well as the resulting simplification for the dynamic routing problem. The problem is transformed into a problem that minimizes link evacuation times. It involves a minimax cost and is equivalent to a linear program admitting a finite solution. A different approach is then taken: a solution based on an infinite algorithm is proposed and used to obtain a complexity of only O(|N|³) per iteration and an exponential rate of convergence to the minimal value. Several optimal routing policies are characterized and formulated. It is found that the store-and-forward feature is not necessary in order to implement a particular optimal routing. Optimality can be achieved by a relatively simple protocol reminiscent of accessing procedures in local area networks. The incorporation of external arrival rates is discussed. Examples are worked out, and suggestions for future work are given     

Restorable dynamic quality of service routing

The focus of quality-of-service routing has been on the routing of a single path satisfying specified QoS constraints. Upon failure of a node or link on the path, a new path satisfying the constraints has to be established. However, resources needed to satisfy the QoS requirements are not guaranteed to be available at the rerouting instant, so QoS is not guaranteed upon failure. Restorable QoS routing, where active and backup paths must be simultaneously set up, has been previously studied. This is mostly motivated by the incorporation of mechanisms to establish QoS guaranteed paths with failure protection in multiprotocol label switching networks. This article describes some previously developed algorithms for dynamic routing of restorable QoS guaranteed paths     

Improved survivability with multi-layer dynamic routing

The article deals with the integrated design and analysis of a telecommunications network to achieve specified levels of survivability under various failure modes and conditions. The main goal of the article is: given a criterion for network survivability, develop a unified theory for network planning at different “layers” of the network, and for coordinated restoration methods after a failure. While most of the discussion relates to modern circuit-switching architectures, for completeness, asynchronous transfer mode technology is also considered     

Improved dynamic routing algorithms in elastic optical networks

The considered Routing, Modulation Level and Spectrum Allocation (RMLSA) problem covers path length minimization while still meeting the spectrum continuity constraints, non-overlapping spectra constraints, spectrum contiguity constraints, and choice of modulation level. In this problem, the relationship between spectrum connection and bit rate of the incoming request has been taken into account. In this paper, two algorithms have been proposed. The first one is based on a set of shortest paths whose lengths are determined by the number of links in the network. The second one is a modified version of Dijkstra’s algorithm. Modification of this algorithm is based on introduction of weights of the network links depending on the utilization of the links and the introduction of a aggregated spectrum of the path that is being selected. Extensive research has shown that algorithms reject the lower traffic volume as compared to well-known algorithms proposed in literature.     

An algebraic theory of dynamic network routing

We develop a non-classic algebraic theory for the purpose of investigating the convergence properties of dynamic routing protocols. The algebraic theory can be regarded as a generalization of shortest-path routing, where the new concept of free cycle generalizes that of a positive-length cycle. A primary result then states that routing protocols always converge, though not necessarily onto optimal paths, in networks where all cycles are free. Monotonicity and isotonicity are two algebraic properties that strengthen convergence results. Monotonicity implies protocol convergence in every network, and isotonicity assures convergence onto optimal paths. A great many applications arise as particular instances of the algebraic theory. In intra-domain routing, we show that routing protocols can be made to converge to shortest and widest paths, for example, but that the composite metric of Internet Gateway Routing Protocol (IGRP) does not lead to optimal paths. The more interesting applications, however, relate to inter-domain routing and its Border Gateway Protocol (BGP), where the algebraic framework provides a mathematical template for the specification, design, and verification of routing policies. We formulate existing guidelines for inter-domain routing in algebraic terms, propose new guidelines contemplating backup relationships between domains, and derive a sufficient condition for signaling correctness of internal-BGP.     

Design and control of networks with dynamic nonhierarchical routing

Dynamic routing concepts are described, and the design and control of dynamic routing networks is discussed. The vastly improved performance of the networks is illustrated with examples from operational experience. The evolution of dynamic routing with respect to several future directions is highlighted. These directions are extension to new networks and services, robust design and real-time adaptivity, and extension to interconnecting networks, including the Worldwide Intelligent Network     

Integrated dynamic distributed routing and admission control in ATM networks

A node-by-node admission control and routing scheme for ATM networks is devised. The scheme is based on the subdivision of traffic into a number of classes, characterized by different performance requirements. At each network node, for all outgoing links, link capacity partitions are periodically assigned to the traffic classes, as the result of an optimization problem over a fixed time interval. Local access control rules compute the maximum number of connections of each class that a link can accept within the assigned capacity. Incoming call connection requests are forwarded in a hop-by-hop fashion. Each node traversed, first checks the presence of resources needed to accept a new connection and guarantee all quality of service (QoS) requirements. This is done by using the local access control rule. Then, it chooses the next node along the path on the basis of a distributed routing strategy. This minimizes a cost function accounting for local instantaneous information, as well as for aggregate information that is passed periodically among adjacent nodes. Two routing strategies are introduced. In the first scheme, a new call is rejected if, at a certain node along the path, there are not enough resources to guarantee QoS requirements, and no recovery mechanism is implemented. In the second scheme, an alternative path is looked for after the first failure. Simulation results are presented which show a comparison between the two proposed routing strategies. Comparison is also made between the proposed scheme and the other approaches. © 1997 John Wiley & Sons, Ltd.     

Resonant self-diffraction from dynamic, laser-induced gratings in II-VI compounds

Dynamic laser-induced gratings (LIG) are investigated in CdS and ZnO. The microscopic processes resulting in the formation of LIG are discussed. A nonlinear coupling is found between oscillators active in the polarizationsoverrightarrow{E} perp overrightarrow{c}andoverrightarrow{E} parallel overrightarrow{c}, respectively. The influence of induced absorption optical bistability on the temporal evolution of LIG is observed and qualitatively discussed.     

基于跳数约束的网络动态路由算法

阐述了网络动态负载平衡和跳数约束条件下寻找最小费用路径的算法,算法中引入了网络中边和点的流量因子的概念,然后利用计算出来的流量因子,定义出每条边的动态费用,这种动态费用包含了网络负载流量的信息.通过综合出来的动态费用,利用一种具有跳数约束计算最小路径的启发式算法,找出最优的可行路径.     

A new metric for dynamic routing algorithms

A dynamic routing algorithm that has as its goal the control of congestion in a packet switching network is presented. The algorithm is based in part on the ARPANET SPF algorithm. However, instead of employing a delay metric, the authors make use of a combination of link and buffer utilizations. A detailed simulation model of the ARPANET was constructed to compare the performance of the congestion-based algorithm to the traditional delay-based (SPF) routing algorithm. The results indicate a substantial improvement in the delay and throughput of the network with the congestion-based routing algorithm     

A distributed delay-constrained dynamic multicast routing algorithm

Many new distributed multimedia applications involve dynamic multiple participants, have stringent end-to-end delay requirement and consume large amount of network resources. In this paper, we propose a distributed delay-constrained dynamic multicast routing algorithm (DCDMR) to support these applications. DCDMR scales well because the source of the multicast tree needs only limited computation or may even not be involved in the route computation. When group membership changes, the existing multicast tree is perturbed as little as possible and the resulting tree cost performance is very satisfactory.     

基于QoS的动态组播路由算法

在分析了网络中基于QoS的组播路由问题的基础上,本文提出了一种新的动态算法,并进行了实验和分析,文中构造的路由方案成功地解决了当网络中存在多个组播及组播节点动态变化情况下的QoS路由选择问题,此方案不仅保证了带宽,端到端延时和延时抖动,优化了路由树的代价,而且有效地控制了算法的复杂性并可适用于大规模的网络中。     

Link failure resilience in the dynamic source routing protocol

Reactive routing protocols for mobile ad hoc networks reduce the routing cost in high mobility environments where link failures are frequent. However, route discovery in these protocols is typically performed via network‐wide flooding, which consumes a substantial amount of bandwidth and causes a significant latency to data packets. To improve the dynamic source routing (DSR) protocol and overcome these limitations, we propose two optimization techniques, viz. generalized salvaging mechanism and cache maintenance using a distributed topology discovery mechanism through mobile ant‐agents. We show, by simulations, that our contributions improve the DSR performance, and particularly in large scale networks with high mobility and heavy load that cause frequent link failures. Copyright © 2008 John Wiley & Sons, Ltd.