WDM Passive Optical Networks With Wavelength Sharing

A wavelength-division-multiplexing-based passive optical network (PON) is demonstrated in which wavelengths can be shared by a flexible number of users on other PONs served from the same central office. Bidirectional transmission is demonstrated through a typical PON at 2.5 Gb/s with wavelength sharing of 16.      

Performance Analysis of Distributed Protocols for Bidirectional Wavelength Reservations in Dynamic WDM Networks

In this paper, we present an analytical model to investigate the blocking performance of distributed wavelength reservation protocols in dynamic WDM networks. This model extends the approach of [S. Arakawa et al., Proceedings of ITC-CSCC, (Sado, Japan, July 1999), pp. 828--831] in two aspects: firstly we take into account the contention between the two end nodes of bidirectional links in bidirectional wavelength reservations. Secondly, we make a distinction between the effects of different kinds of network delays, which include signaling transmission delay, signaling processing delay, and optical cross-connects (OXC) operation delay. As an application, we use our method to analyze the performance of two different signaling processing schemes, namely forward after cross-connect (FAXC) and forward before cross-connect (FBXC) [M. Goyal et al., Technical Digest of OFC2002 (Anaheim, CA, Mar. 2002) pp. 489--490]. The accuracy of our analytical model is validated by discrete-event simulations. Numerical results show that the FBXC scheme can give a lower network blocking probability than FAXC, and the efficiency of FBXC becomes more significant as the OXC operation delay increases.     

Wavelength assignment for WDM ring

A novel wavelength assignment method for a WDM ring is proposed. The new method can easily assign each wavelength directly and visually to specific connections on an N-node ring graph without the aid of any table or matrix or computer. A simple explicit formula for determining the assigned wavelength index for any node-pair connection is also given. The presented WLA method is more attractive in many aspects than other wavelength assignment methods that have been reported previously for a WDM ring.     

Performance Study of Distributed Wavelength Reservation Protocols within Both Single and Multi-Fiber WDM Networks

Distributed wavelength reservation protocols are employed to dynamically set up and tear down lightpaths in WDM networks. In this paper, discrete event-driven simulations are carried out to investigate the performance of different protocols under both single and multi-fiber circumstances. Simulation results indicate that the behavior of these protocols varies noticeably between single and multi-fiber networks. Discussions on these results are also presented. It is found that the preferred scheme in the literature, which adopts backward reservation with random wavelength selection, does well in single-fiber scenarios. But this scheme fails to be excellent in multi-fiber scenarios since it cannot take full advantage of multiple fibers. Then, we extend the reservation protocols for multi-fiber networks and propose a novel wavelength selection policy called Maximum-Availability policy. Results show that our scheme will give an outstanding performance in both single and multi-fiber networks.     

Wavelength conversion technologies for WDM network applications

WDM networks make a very effective utilization of the fiber bandwidth and offer flexible interconnections based on wavelength routing. In high capacity, dynamic WDM networks, blocking due to wavelength contention can he reduced by wavelength conversion. Wavelength conversion addresses a number of key issues in WDM networks including transparency, interoperability, and network capacity. Strictly transparent networks offer seamless interconnections with full reconfigurability and interoperability. Wavelength conversion may be the first obstacle in realizing a transparent WDM network. Among numerous wavelength conversion techniques reported to date, only a few techniques offer strict transparency. Optoelectronic conversion (O/E-E/O) techniques achieve limited transparency, yet their mature technologies allow deployment in the near future. The majority of all-optical wavelength conversion techniques also offer limited transparency but they have a potential advantage over the optoelectronic counterpart in realizing lower packaging costs and crosstalk when multiple wavelength array configurations are considered. Wavelength conversion by difference-frequency generation offers a full range of transparency while adding no excess noise to the signal. Recent experiments showed promising results including a spectral inversion and a 90 nm conversion bandwidth. This paper reviews various wavelength conversion techniques, discusses the advantages and shortcomings of each technique, and addresses their implications for transparent networks     

Efficient Wavelength Assignment Algorithms for Light Paths in WDM Optical Networks With/Without Wavelength Conversion

In order to reduce the overall wavelength number required in a wavelength division multiplexing (WDM) network with static traffic loading, new heuristic algorithms for wavelength assignment are proposed in this paper. A new parameter called one-wavelength-decrease cost is defined and used to compare the efficiency of these algorithms. Comparative simulation studies have been carried out for various network topologies to investigate the effectiveness of the proposed algorithms.     

WDM光网络中波长转换技术的研究

波长转换是ＷＤＭ 光网络中一项重要的基础技术。在大型光网络中,它通过波长重用,可以降低网络中因波长竞争而导致的阻塞,提高网络管理、控制和维护的灵活性。文中系统地论述了波长转换技术,首先介绍了ＷＤＭ 光网络中波长转换的必要性,随后分析各种不同的波长转换技术原理,讨论其主要性能及优缺点     

WDM网络中一种考虑优先级的波长分配算法

提出了一种在多优先级的情况下,基于RCL算法来提高网络流量的波长分配新算法.文章对于具有相同优先级的光路建立请求时,采用相对容量损失的RCL法分配波长,而对于不同优先级的光路请求,通过调整门限值来保证网络尽可能地接纳更多低优先级的网络流量.仿真结果表明,当负载较高时,多接纳的网络流量已十分明显.     

Dynamic Wavelength Assignment for WDM All-Optical Tree Networks

We develop an on-line wavelength assignment (WA) algorithm for a wavelength-routed WDM tree network. The algorithm dynamically supports all$bf k$-port traffic matrices among$N$end nodes, where$bf k$denotes an integer vector$[k_1 ldots, k_N]$and end node$i, , 1leq ileq N$, can transmit at most$k_i$wavelengths and receive at most$k_i$wavelengths. Our algorithm is rearrangeably nonblocking, uses the minimum number of wavelengths, and requires at most$d^ast-1$lightpath rearrangements per new session request, where$d^ast$is the degree of the most heavily used node. We observe that the number of lightpath rearrangements per new session request does not increase as the amount of traffic$bf k$scales up by an integer factor. In addition, wavelength converters cannot reduce the number of wavelengths required to support$bf k$-port traffic in a tree network. We show how to implement our WA algorithm using a hybrid wavelength-routed/broadcast tree with only one switching node connecting several passive broadcast subtrees. Finally, using roughly twice the minimum number of wavelengths for a rearrangeably nonblocking WA algorithm, we can modify the WA algorithm to be strict-sense nonblocking.     

带电流分配和LDO控制的双路同步PWM控制器IRU3046

IRU3046是IR公司推出的一款集成有一个双路同步冲跳控制器和一个线性调节控制器的PWM控制器，该芯片可以为多输出应用系统提供高性能、低价位，灵活的电源解决方案，它具有两个相互独立的输出通道，并可利用外部元件对其开关频率和输出电压进行编辑设计，文中介绍了IRU3046的引脚功能、工作原理和设计要点，给出了IRU3046的典型应用电路。     

Wavelength routing with spare reconfiguration for all-optical WDM networks

This study presents a wavelength-routing scheme with spare reconfiguration (SR) to construct dependable all-optical wavelength-division-multiplexing (WDM) networks. Path protection using shared spare lightpaths is a general wavelength-routing method for reducing blocking probability while minimizing demand for spare resources. However, in a dynamic traffic environment, this method may still yield a poor performance because a wavelength on a link is very likely to be continuously held by a spare lightpath and to be unable to be assigned to the working lightpath of a new connection. This study develops a spare reconfiguration mechanism with wavelength reassignment (SR/spl I.bar/WR) and path reassignment (SR/spl I.bar/PR) to make the spare dynamic and thus further reduce the blocking probability. The proposed wavelength routing with SR proceeds in three stages and has polynomial time complexity. Extensive simulation experiments were conducted on the NSFNET and the K5 fully connected network to investigate the performance of the proposed wavelength routing with SR. Results of this study show that the proposed wavelength routing with SR can reduce the blocking probability compared with the general wavelength routing with just shared spare lightpaths by choosing a positive tuning cost. In addition, the improvement of the blocking performance is maximized when using SR/spl I.bar/WR followed by SR/spl I.bar/PR.     

Strictly Non-Blocking All-Optical-Cross-Connect Demonstrator for WDM Wavelength Path Networks

In this paper, we assess the design and performances of a strictly non-blocking all-optical cross-connect demonstrator node for WDM wavelength path networks. The all-optical cross-connect (AOXC) prototype was experimentally tested in a small 2 x 2 WDM network with a STM-16 bit stream per channel. The single and cascaded performance of the AOXC was also simulated and its results were validated with the experimental ones.     

波分复用光网中的一种新型波长分配算法

目前网络承载业务的趋势是以IP为中心的数据业务,从而促进了以WDM光网络向高速和宽带多波长的应用和普及,为了进一步提高网络的性能并提高资源利用率,出现了光网络控制面技术.路由选择与波长分配问题是WDM光传输网络控制面中非常重要的问题之一.目前实际应用最广泛的波长分配算法是First-Fir(FF)算法.本文基于FF算法,研究动态业务下波分复用光网络在固定选路下的波长分配问题,提出了一种新的波长分配启发式算法——Joint First Fit.计算机仿真试验表明,与常用的FF算法相比,该算法显著的降低了网络呼叫阻塞率,有利于提高网络资源的利用率.     

一种基于WDM四纤环网的波长分配算法

介绍了一种基于WDM四纤共享保护环网进行波长分配的算法.该算法采用矩阵形式表示波长分配情况,它可以用最少的波长数目经由最短通道实现环网上各站点之间的全连接.最后,对偶数站点的波长分配方法加以改进,用比较简洁的过程获得了相同的波长分配结果.     

基于分立衍射光栅的波分复用(解复用)器

波分复用(解复用)器是光通信中重要的无源器件。对目前常用的波分复用(解复用)技术进行了综述,着重介绍了一种新颖的波分复用(解复用)技术,基于分立衍射光栅的波分复用(解复用)技术,并介绍了它所克服的技术难点以及目前它所达到的技术水平。     

Improved Performance Analysis for Synchronous Single-Hope WDM Networks

This note extends the work in the paper [1] and presents a precise method without simplifications of the receiver collision analysis for the synchronous transmission protocols in the well known Passive Star WDM topology.     

WDM网络中一种新型的波长路由算法

提出了一种新的波长选路算法-HCW算法,该算法综合考虑光路径跳数(H)、全网拥塞程度(C)以及链路最少剩余波长数(W)三个因素对路径选择的影响。对NSF网络的计算机仿真结果表明,该算法性能优于FAR(Fixed-Alternated Routing)、FPLC(Fixed Paths Least Congest)算法。     

Modified ShuffleNet for Multihop All-Optical WDM Networks Employing Wavelength Reuse

A modified multihop ShuffleNet configuration for WDM all-optical networks is described which is rearrangeable and allows wavelength reuse at each node as it expands. This configuration does not require any rearrangement of preceding node and wavelength assignments when new nodes and wavelengths are added and it can function with fewer overall number of nodes. By comparison, the traditional Perfect ShuffleNet requires a large number of nodes to be available for any updating of the configuration. Most of these nodes remain idle during the normal signal routing process leading to reduced network link capacity. Furthermore, to facilitate wavelength reuse when updating, the Perfect ShuffleNet necessitates the rearrangement of preceding node and wavelength assignments. This leads to generalized forms of ShuffleNet where wavelength reuse forces network architecture into irregular topologies. The modified ShuffleNet proposed here is capable of facilitating wavelength reuse without the modification of initial node and wavelength assignments and could be realised by using a star topology.     

一种波长转换受限WDM网络的动态路由和波长分配算法

本文基于分层图模型,提出了在节点波长转换范围受限和波长转换器数目受限情况下,解决WDM网络的动态路由和波长分配问题的一种算法.通过计算机仿真,研究了本算法的性能以及这两种波长转换受限情况对网络阻塞率的影响.