WDM系统的监控技术分析

在介绍波分复用系统基础之上说明了光监控信道存在的合理性和必要性 ,详细分析了带内波长监控技术和带外监控技术的实现机制、功能特征及适用环境 ,最后归纳了实现 WDM系统管理应值得注意的一些相关因素     

FPGA在波分复用系统光监控信道中的应用

在波分复用系统中,光监控信道用来传送网管信息。介绍了一种WDM(波分复用)光监控信道的设计方法,使用Altera FPGA(现场可编程门阵列)完成光监控信道板的核心功能。发送部分主要由时钟模块、HDLC(高级数据链路控制)和E1时序产生及成帧模块、NRZ(不归零码)/CMI(传号反转码)、公务电话处理模块和单片机时序发生模块组成,接收部分包括时钟模块、E1帧同步检测与HDLC标志字检测处理模块、NRZ/CMI解码模块等。设计采用自顶向下的方法,各功能模块由VHDL语言设计完成。该设计已经成熟应用在实际的WDM系统中。     

WDM光网络中的业务量疏导

波分复用（WDM）技术在主干传送网中巳广泛应用，WDM光网络的研究进展也非常迅速，光网络中的业务量疏导定义为复用、解复用和交换低速率业务流到大容量的光路中的行为。介绍了WDM光网络的业务量疏导的重要性，研究方法及其最新研究进展情况。     

WDM光网络的规划方法

近年来,光纤传输技术的发展使网络传输带宽不断增长,特别是波分复用(WDM)技术的引入使电信运营商可以把他们的网络容量提高数十倍。新技术的使用为网络设计和规划提出新的课题,作者主要讨论骨干WDM传送网的规划方法。     

一种改进遗传算法在WDM光网络中的应用

在波长路由光网(WRON)中,波长转换对提高网络性能、减少阻塞率起着重要的作用.但由于目前全光波长转换器非常昂贵,因而如何最优利用波长转换是配置光网络的一个重要问题.文中利用遗传算法很好地解决了这一问题,并且利用数值模拟的方法,计算了美国自然科学基金网(NSFnet)网络中最优配置下网络的阻塞情况.然后针对普通遗传算法的缺点,提出了一种改进遗传算法.最后利用数值模拟的方法,比较了两种算法的性能.     

WDM光网络关键技术研究(续前)

信息爆炸导致了对带宽的无限需求,而波分得用（WDM）系统在满足不同增长的带宽需求的同时还具有不同可比拟的联网优势,文中着重研究了WDM光网络的关键技术。     

OTU在WDM中的使用

OTU在WDM系统中占据重要地位，对其进行研究有可能优化WDM和SDH系统。本文介绍了OTU的概念，特点及其运用。     

近阶段WDM网络技术的发展与应用

首先简要介绍了WDM技术,之后讨论了WDM环网和智能光网络,最后介绍了WDM技术在国内外的发展情况。     

WDM城域光传送网的网络管理

基于wDM的光网络由于承载的信息量非常巨大，网络的任何故障和失效都将造成严重的后果，因此研究这种网络的网络管理十分重要。在叙述了基于wDM技术的光网络的网络管理体系结构和特殊要求之后，着重对其网络开销的传送技术-光监控信道(OSC)技术进行了研究，井进一步探讨了光城域网环境下的OSC技术。     

N×10Gbit/s WDM系统与智能(自动)光网络

本文就N×10Gbit/s WDM系统主要技术要点光信噪比(OSNR)、FEC功能、L波段等进行了详细讨论,另外介绍了国际上智能(自动)光网络的新发展,特别是波长路由协议,并对我国发展这两项技术提出了建议.     

A scheduling application for WDM optical networks

Optical networking using WDM technology has matured considerably, and commercial WDM network equipment and WDM network control and management prototypes have appeared. To use such a network efficiently, a scheduling facility and its enabling mechanisms have to be provided. This scheduling facility should be integrated to interoperate with the rest of the network control and management software such as connection manager or signaling daemon. We present a scheduling application to address this need. The architecture for the application and its key components are presented. Agent-related enabling mechanisms are introduced to monitor the optical signal quality and collect performance measurements. A resource broker is used to manage the communication and interoperability between agents and the application. An event service is developed to decouple the communication between the agents and the scheduling application, and to enable the communication among the agents themselves. The scheduling application consists of the quality of signal information and threshold objects, current network usage, history data module, scheduling module, and access to a performance database. To provide traffic control and high network resource utilization, the application is equipped with wavelength scheduling algorithms. An experimental study for the basic scheduling algorithms has been conducted over the MONET DC network.     

三种WDM光网络信道预测算法的比较

分别介绍了三种避免冲突的波分复用星形光网络调度算法,并对这三种WDM光网络信道预测算法作了全面的分析,最后在统一环境下做了仿真和比较.结果显示其中一种算法与其它两种算法相比,不仅提高了信道利用和网络吞吐量,而且减少了数据包的平均等待时间.     

基于波长路由的卫星光网络研究

为实现卫星通信的突破性发展,扩大卫星通信容量和带宽,建立了新型的卫星网络模型,分析了卫星光网络的技术难点问题,利用副载波和光波的双层路由方案,进一步提出了卫星光网络的新思路和实现方案.     

Study of optical control plane for translucent WDM networks

In this article, we concentrate on the study of control plane and management approaches for translucent WDM networks. A hybrid optical control plane (OCP) is proposed, which needs the extensions of both routing and signaling protocol, to combine the best features of routing-based information updating and signaling-based data collection and path evaluation. Simulations are conducted to compare hybrid OCP with two existing control architectures: signaling-based OCP and routing-based OCP. Numerical results show that hybrid OCP exhibits a lower blocking probability than the other approaches, and also minimizes the stability and scalability problems under various traffic conditions.     

Protection interoperability for WDM optical networks

The failure of a single optical link or node in a wavelength division multiplexing (WDM) network may cause the simultaneous failure of several optical channels. In some cases, this simultaneity may make it impossible for the higher level (SONET or IP) to restore service. This occurs when the higher level is not aware of the internal details of network design at the WDM level. We call this phenomenon “failure propagation.” We analyze three types of failure propagation, called “bottleneck,” “connectivity,” and “multiple groups.” Then we present a solution based on the definition of appropriate requirements at network design and a WDM channel placement algorithm, protection interoperability for WDM (PIW). Our method does not require the higher level to be aware of WDM internals, but still avoids the three types of failure propagation mentioned above. We finally show the result on various network examples     

WDM光网及多层网络生存性的研究

为了适应多层次网络发展的需要，在讨论WDM光层生存性机制的基础上，针对多层网络联合的生存性机制进行了仔细的分析，提出了一种多层协调的实现办法，并讨论了多层空闲资源设计中的共享问题。     

Design protection for WDM optical networks

With wavelength division multiplexing (WDM) networks the failure of a single link or component may cause the simultaneous failure of several optical channels, potentially making impossible restoration by rerouting directly in higher layers directly using the optical network (SDH, ATM, internal protocol (IP)). To address this, we introduce the concept of design protection, which aims at making such failure propagations impossible. We present the disjoint alternate path (DAP) algorithm which places optical channels in order to maximize design protection. We show the result on various network examples     

Provisioning algorithms for WDM optical networks

This paper concerns connection provisioning for optical networks employing wavelength division multiplexing. A heuristic algorithm is developed and numerically studied for routing and wavelength assignment of a set of static connection requests. The algorithm runs much faster than the optimum solution of this problem. An adaptation of the algorithm is proposed to design restorable networks which can handle a specified set of failures. The proposed algorithm is based on taking all failures into consideration simultaneously, and performs better than developing independent designs for each failure     

A channel reuse strategy with adaptive channel allocation for all-optical WDM networks

The fundamental problems of WDM networks are: (1) high rate of control packet loss and (2) high propagation delay for each (re)transmission. In this paper, we minimize the station randomness to access the control architecture introducing a collisions-free access scheme. We propose a synchronous protocol according which at the end of the propagation delay each station applies a distributed algorithm for packet transmission following the data channel collisions and the receiver collisions avoidance algorithms. We introduce two data transmission stages. The time difference between them is one packet transmission time. At the end of the first stage all data channels are free and can be reused by the remaining data packets during the second stage. The proposed protocol ensures a totally collisions-free performance. The main advantage is that the data channels reuse strategy applied during the second stage provides enhanced transmission probability to the rejected packets during the first stage. This allows the data packets to try retransmission in the same cycle without requiring control packets re-coordination that increases propagation delay. Thus, we achieve large number of data packets transmission, even more than the data channels number, providing throughput improvement and delay reduction, comparing with other studies.     

Differentiated QoS for survivable WDM optical networks

Optical networks based on WDM technology have become a promising solution to realize transport networks that can meet the ever-increasing demand for bandwidth. As WDM networks carry a huge volume of traffic, maintaining a high level of survivability is an important and critical issue. The. development of GMPLS switching technology led to the direct integration of IP and WDM. In these IP-over-WDM networks different applications/end users need different levels of fault tolerance and differ in how much they are willing to pay for the service they get. The current trend in network development is moving toward a unified solution providing support for voice, data, and various multimedia services. Therefore, it imperative that WDM networks incorporate fault tolerance to single or multiple component failures, protection bandwidth, recovery time, and recovery granularity besides resource utilization and call acceptance ratio. This article presents a survey of various methods that have been proposed for providing service differentiation in survivable WDM networks and discuss their performance. Such methods are broadly classified under various paradigms such as differentiated reliability, R-connections, quality of protection, and quality of recovery.