一种基于WDM光网络的静态波长路由优化算法

研究了WDM光网络中的静态波长路由问题,基于负载的均衡可以改善网络的性能这一事实,提出了一种优化的路由算法(O-Spread算法),文中进行了算法仿真,结果表明优化算法与传统的最短路由算法相比,能够有效地减小网络对于波长数目的需求。     

Reliability analysis of an optical ATM switch based on wavelength routing

Reliability studies of a demonstrated asynchronous transfer mode (ATM) switch with all-optical packet routing are presented. Calculations are based on available reliability data for commercial components. An additional inherent redundancy is shown to improve switch availability. Our calculation results further show that a proposed multiplane switch satisfies the general reliability requirement for switching systems.     

Multicast routing and wavelength assignment in multihop optical networks

This paper addresses multicast routing in circuit-switched multihop optical networks employing wavelength-division multiplexing. We consider a model in which multicast communication requests are made and released dynamically over time. A multicast connection is realized by constructing a multicast tree which distributes the message from the source node to all destination nodes such that the wavelengths used on each link and the receivers and transmitters used at each node are not used by existing circuits. We show that the problem of routing and wavelength assignment in this model is, in general, NP-complete. However, we also show that for any given multicast tree, the wavelength assignment problem can be solved in linear time.     

Fixed-alternate routing and wavelength conversion inwavelength-routed optical networks

Consider an optical network which employs wavelength-routing crossconnects that enable the establishment of wavelength-division-multiplexed (WDM) connections between node pairs. In such a network, when there is no wavelength conversion, a connection is constrained to be on the same wavelength channel along its route. Alternate routing can improve the blocking performance of such a network by providing multiple possible paths between node pairs. Wavelength conversion can also improve the blocking performance of such a network by allowing a connection to use different wavelengths along its route. This work proposes an approximate analytical model that incorporates alternate routing and sparse wavelength conversion. We perform simulation studies of the relationships between alternate routing and wavelength conversion on three representative network topologies. We demonstrate that alternate routing generally provides significant benefits, and that it is important to design alternate routes between node pairs in an optimized fashion to exploit the connectivity of the network topology. The empirical results also indicate that fixed-alternate routing with a small number of alternate routes asymptotically approaches adaptive routing in blocking performance     

An analysis of limited wavelength translation in regularall-optical WDM networks

We analyze limited-wavelength translation in regular all-optical, wavelength division multiplexed (WDM) networks, where up to W wavelengths, each of which ran carry one circuit, are multiplexed onto a network link. All-optical wavelength translators with a limited translation range permit an incoming wavelength to be switched only to a small subset of the outgoing wavelengths. We focus on the wraparound mesh and hypercube WDM networks, and analyze the case where an incoming wavelength can he switched to one of k (k=2, 3) outgoing wavelengths (called the feasible wavelength set). Our analysis captures the state of a feasible wavelength set at a network node, which allows us to obtain the probability that a session arriving at a node at a random time successfully establishes a connection from its source node to its destination node in each of these topologies. Based on this probability, we quantify the throughput and blocking performance of limited wavelength translation, and compare it to that of no wavelength translation and full wavelength translation. We demonstrate that in regular networks it can obtain most of the performance advantages of full translation at a fraction of the cost, and we present a simple, economical switch architecture to effect limited wavelength translation at a cost that is effectively independent of the number of wavelengths W in the system     

Single and double distributed optical amplifier fiber bus networkswith wavelength division multiplexing for photonic sensors

This paper presents numerical simulations of single and dual fiber bus networks with distributed amplification, which are used for the wavelength division multiplexing of photonic sensors. The model upon which the simulations are based has been compared to a previously published experimental result and good agreement has been obtained. A novel technique for allocating the signal wavelength to the sensor position in order to equalize the received signal power is also discussed     

Virtual-node-based multicast routing and wavelength assignment in sparse-splitting optical networks

This paper investigates several problems associated with optical multicast routing and wavelength assignment in sparse-splitting optical networks for interactive real-time media distribution. Unfortunately, the constrained multicast routing with optimized wavelength assignment leads to NP-complete condition. Thus, in this paper, a virtual-node-based multicast routing algorithm is first proposed to satisfy the requirements of interactive real-time multicasting as well as the constraints from underlying optical networks. For the constructed multicast tree, we then associate an effective wavelength assignment algorithm. The experimental results show that the proposed algorithm combination performs well in terms of (1) the wavelength channel cost, (2) the maximum variation of inter-destination node delays, (3) the signal quality, and (4) the number of wavelength conversions.     

A synthetic algorithm for wavelength routing in optical network

After analyzing the merits and shortcomings of Fixed-Alternated Routing algorithm （FAR） and Least Loaded Routing algorithm （LLR）, we propose one novel dynamic optical routing algorithm. Having considered the influences of path＇s length and path＇s congestion just like in FAR and LLR, we take into account the network resource status-amount of free wavelengths in the network. Proposed algorithm sets up connections on three possible paths according to amount of available free wavelengths in the network, which effectively decreases the blocking probability. The National Science Foundation （NSF） network and mesh-torus network simulation results show that the performance of this algorithm is better than that of FAR and LLR.     

Optical wavelength routing, translation, and packet/cell switchednetworks

We study several models for fixed-size packet/cell switching (e.g., 53 bytes for asynchronous transfer mode) in wavelength routed optical networks with an emphasis on throughput performance analysis. In particular, we examine the associated trade-offs between functionality and hardware complexity. The basic model here is a two-sided “switch” or sorter. Cells generated at user inputs destined for user outputs are allowed to reach their destinations by recirculation or multihop through a fixed wavelength routed optical network a number of times. Using algebraic techniques, we analyze the basic model and its variations that use different types of wavelength translation for their capability to achieve permutations of cells from inputs to outputs. In particular, we showed that when cell-by-cell wavelength translation functionality is allowed, the number of recirculations in the network to achieve all permutations is 3 log_W N where W is the number of wavelengths. The resultant normalized per user throughput of 1/3 log_W N is close to the conjectured optimal of 1/(2 log_W N-1) under the conditions specified in the model. Finally, using another model we show that it is possible to achieve a normalized per user throughput of 1 and we calculate the amount of extra hardware required for this purpose     

An ARROW optical wavelength filter: design and analysis

A novel ARROW (antiresonant reflecting optical waveguide)-based optical wavelength filter is proposed. The modal characteristics of the coupled ARROW structures is analyzed rigorously by the transverse resonance method. As an alternative configuration to the conventional directional coupler filter, the proposed device features large core size compatible with fiber and nearly periodic dependence of the coupling-length on the waveguide separation, which provides more flexibility for fabrication of the device. A design procedure for this type of coupled ARROW structure used for wavelength filtering is presented. The devices designed are simulated and verified by the beam propagation method. An ARROW wavelength filter based on SiO₂/TiO₂ has a FWHM bandwidth narrower than 7 Å     

一种基于改进蚁群算法的光网络动态RWA机制

动态RWA(路由与波长分配)问题是智能光网络的核心问题.文章提出一种解决动态RWA问题的改进蚁群算法,在转移概率中加入了链路的空闲率作为约束条件,同时还引入了随机扰动防止搜索过早收敛于局部最优路径.仿真结果表明,改进算法与传统Dijkstra+ FF(首次命中)算法相比,可以显著降低阻塞率,提高资源利用率.     

波长路由光网络中RWA算法的设计分析

文章通过对波长路由光网络中路由与波长分配(RWA)问题的研究,介绍了求解路由子问题和波长分配子问题的常用方法,总结了3种类型的RWA问题的优化解决方法,最后对目前RWA算法设计中存在的问题进行了分析并阐述了解决此类问题的重要性.     

光网中路由与波长分配问题的一种新模型

路由与波长分配问题是波分复用光网中的一个关键问题.文章从经济学的角度出发提出了路由与波长分配问题的一种数学模型,并且进行了分析和仿真.结果表明,模型较大程度地反应了现实,对网络运营商而言很有参考价值.     

Blocking performance analysis on adaptive routing over WDM networks with finite wavelength conversion capability

Analytical blocking probability analysis is important for network design. In this paper, we present an analytical model for the blocking probability analysis on adaptive routing over the WDM networks with finite wavelength conversion capability. Modeling the finite nature of wavelength conversion has been a difficult task. We make use of the idea of segmented route to handle the finite wavelength conversion property. In this approach, a route is divided into a number of segments separated by wavelength converting nodes. We then combine the single-link model and the overflow model to derive the network-wide blocking probability. There are two distinct features in our technique. First, a concept of segmented route is used. Second, link state is considered when calculating the traffic flow. The latter ensures that the analytical results match closely to practical network status. Extensive simulations show that the analytical technique is effective in modeling the blocking probability performance for sparse networks.     

全光网静态路由选择和波长分配的分层图算法

文章提出一种将路由选择和波长分配结合起来的启发式的路由选择和波长分配(RWA)算法．通过这种新的分层图算法和限制光跳距的加权系数来优化全光网的静态路由选择和波长分配，使建立光连接时所需的波长数达到最少．最后对实际的ARPANet等5种光网络进行了计算机仿真，证明了本算法比以前的算法有更好的性能．     

Distributed dynamic grooming routing and wavelength assignment in WDM optical mesh networks

The bandwidth of a wavelength channel in WDM optical networks is very high compared to the user’s requirements for various applications. Therefore, there is a scope for better utilization of channel bandwidth by traffic grooming, in which several user’s channels are multiplexed for transmission over a single channel. Several research works have been reported on traffic grooming routing and wavelength assignment (GRWA) for static and dynamic traffic pattern under centralized environment. Distributed dynamic grooming routing and wavelength assignment (DDGRWA) is a new and quite unexplored area in WDM optical mesh networks. This article introduces the concept of distributed traffic grooming in WDM mesh networks which also includes virtual topology construction, reconfiguration, routing and wavelength assignment in the distributed environment assuming incoming traffic to be dynamic in nature. We have also presented simulation results of our algorithm on dynamically generated traffic under various network topologies.     

A practical approach for routing and wavelength assignment in largewavelength-routed optical networks

We consider large optical networks in which nodes employ wavelength-routing switches which enable the establishment of wavelength-division-multiplexed (WDM) channels, called lightpaths, between node pairs. We propose a practical approach to solve routing and wavelength assignment (RWA) of lightpaths in such networks. A large RWA problem is partitioned into several smaller subproblems, each of which may be solved independently and efficiently using well-known approximation techniques. A multicommodity flow formulation combined with randomized rounding is employed to calculate the routes for lightpaths. Wavelength assignments for lightpaths are performed based on graph-coloring techniques. Representative numerical examples indicate the accuracy of our algorithms     

Dynamic routing and wavelength assignment with optical bypass using ring embeddings

We consider routing and wavelength assignment in ring, torus, and tree topologies with the twin objectives of minimizing wavelength usage and maximizing optical bypass. The P-port dynamic traffic assumption is used, which allows each node to send and receive at most P calls. For rings we show that PN/4 wavelengths are necessary and sufficient, and provide a four-hub ring architecture that requires only half of these wavelengths to be locally processed. We extend this approach to develop RWA and bypass algorithms for both tori and trees by embedding virtual rings within these topologies and applying the ring algorithms. For an R×C torus, we embed R+C rings onto the torus and provide an approach to RWA and banding based on solving disjoint RWA/banding problems for each ring. Our RWA algorithm is more wavelength efficient than any currently known algorithm and uses the minimum number of wavelengths for R≥2C. Our subsequent banding algorithm allows half of these wavelengths to bypass all but 4R hub nodes. Finally, we give a RWA for trees that embeds a single virtual ring and uses the ring to obtain a RWA that requires no more than PN/2 total wavelengths; this figure is shown to be optimal for balanced binary trees. A banding algorithm follows that allows half these wavelengths to bypass all non-hub nodes.     

Low-latency optical network based on wavelength division multiplexed clockwork routing

Optical networks based on the ‘clockwork’ routing mechanism have significant advantages for high-speed optical packet switched applications in which latency is critical, such as parallel and distributed computing. The main advantages are that no optical buffers and no centralized contention arbitration are required. However, the network performance decreases rapidly with increasing network size. This article proposes the use of wavelength division multiplexing, in combination with clockwork routing, to provide significant improvements in network scalability and bisection bandwidth, resulting in higher throughput and reduced latency.     

A performance model of deflection routing in multibuffer networkswith nonuniform traffic

Deflection routing can be used in networks whose stations have the same number of input and output links. Fixed length packets arrive synchronously on the station's input links at the beginning of time slots, and each packet is routed via the output link that offers the shortest path to its destination. Since the number of packet buffers at each output link is finite, the simultaneous contention of two packets for the last buffer of a common output link must be resolved by “deflecting” one of the packets to another output link. Thus, the deflection of a packet could result in the packet following a route that is not a shortest path. The potentially unbounded number of routes that a given packet can take makes analyzing the performance of such networks difficult. In particular, there are no analytical models that can analyze multibuffer deflection-routing networks with nonuniform traffic. Using independence assumptions, the authors develop a performance model of deflection routing that allows to estimate accurately and efficiently the mean transport time and throughput in a network that has any given two-connected topology, multiple buffers at each output port, and an arbitrary traffic matrix