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。     

光纤布拉格光栅在光脉冲压缩中的应用

光纤布拉格光栅(FBG)由于其独特的光学特性和灵活的设计特点,在光通信系统中有着广泛的应用,包括光脉冲压缩、全光开关、全光复用/解复用器、色散补偿器和光存储等等.文章主要对FBG在光脉冲压缩中的应用进行了分析,并对几种压缩器的结构、原理和性能作了介绍.     

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。     

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     

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     

啁啾光纤光栅波长路由光网络的组播功能实现

在基于光路交换的4节点16×10 Gbps双纤单向新型分布式全光自愈环网上,利用啁啾光纤光栅(CFBG)和环行器等无源器件实现了光层组播,避免了光/电/光转换.CFBG在网络中用于实现色散补偿、上下话路和波长路由.通过调节光栅的中心波长,分别完成对控制信息、组播业务信息的分别读取.整个网络不存在关键性节点,每个节点都可以作为组播业务的发起端和接收端.根据控制信息配置传输信道,提高了组播数据流的传输效率.研究结果表明,这种组播方式具有物理实现简单、安全性高、对组播数据速率和格式透明以及数据传输无阻塞等特点.     

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     

阵列波导光栅器件的发展与应用

密集波分复用（ＤＷＤＭ）是光纤通信中的关键技术,而阵列波导光栅（ＡＷＧ）在波分复用系统中有 广泛的应用。本文综述了ＡＷＧ的原理以及它的发展和光纤通信系统中的应用。     

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.     

动态路由模拟策略研究

网络模拟路由策略的基本目标是真实地反映模拟数据包的转发过程。拓扑变化会影响路由选择结果。现：有模拟器在处理动态路由时会让所有节点同时感知到拓扑变化信息，这与实际网络中的情况并不相符。给出并分析动态路由模拟抽象模型，进而提出计算不同节点对拓扑变化感知时间的策略；提出动态MTree_Nix路由策略，以静态路由表和拓扑变化消息序列作为动态路由表，通过比较节点的感知时间查找路由。实验结果表明，此算法能够更真实地模拟网络中的动态路由，并且具有较高的模拟效率。     

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.     

动态干涉仪的位相光栅衍射效率研究

为了解决普通二维光栅在动态干涉术中光能量利用不足的问题,使用标量衍射理论和傅里叶分析法对矩形正交位相光栅和棋盘型位相光栅的衍射效率进行推导,分别对两种光栅的最佳工作级次选择策略进行研究。分析结果表明,当分光器件为矩形正交位相光栅时,应选择(0, 1)级与(1,0)级作为动态干涉仪的工作级次,光能量利用率达到54.4%;当分光器件为棋盘位相光栅时,应选择(1,1)级作为动态干涉仪的工作级次,光能量利用率达到65%。实验对比了两种光栅在动态干涉仪上的应用效果,当选用(1,1)级作为工作级次时,结果表明使用棋盘型位相光栅的应用效果优于矩形正交位相光栅。因此在动态干涉仪中使用棋盘位相光栅并选用(1,1)级作为工作级次能够消除光能量利用不足对测量造成的影响。     

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.     

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.     

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