基于服务器系统模型的光网络容量分析

In this paper, a new architecture of optical networks -- the optical network based on server system is considered. From the point of this new architecture, the network can be modeled as a server system with three type servers -- the access server, the node server and the link server. The network performances such as cost, energy consume and network capacity can be affected by the capability of these three type servers. New ILP formulations are proposed to analyze the network capacity under two types of node severs, with and without wavelength converter. Computer simulations are conducted to evaluate the effectiveness of these new formulations. The study has shown that the network can achieve the same throughput under the two types of node servers and the network throughput increases when the maximum allowed variation increases.     

Multicast Capacity of Packet-Switched Ring WDM Networks

Packet-switched unidirectional and bidirectional ring wavelength division multiplexing (WDM) networks with destination stripping provide an increased capacity due to spatial wavelength reuse. Besides unicast traffic, future destination stripping ring WDM networks also need to support multicast traffic efficiently. This article examines the largest achievable transmitter throughput, receiver throughput, and multicast throughput of both unidirectional and bidirectional ring WDM networks with destination stripping. A probabilistic analysis evaluates both the nominal capacity, which is based on the mean hop distances traveled by the multicast packet copies, and the effective capacity, which is based on the ring segment with the highest utilization probability, for each of the three throughput metrics. The developed analytical methodology accommodates not only multicast traffic with arbitrary multicast fanout but also unicast and broadcast traffic. Numerical investigations compare the nominal transmission, receiver, and multicast capacities with the effective transmission, receiver, and multicast capacities and examine the impact of number of ring nodes and multicast fanout on the effective transmission, reception, and multicast capacity of both types of ring networks for different unicast, multicast, and broadcast traffic scenarios and different mixes of unicast and multicast traffic. The presented analytical methodology enables the evaluation and comparison of future multicast-capable medium access control (MAC) protocols for unidirectional and bidirectional ring WDM networks in terms of transmitter, receiver, and multicast throughput efficiency.     

波分复用环网中带内串扰的精确分析

分析了波分复用 (WDM)全光通信环网中的串扰起因 ,指出单纤 WDM环网中的串扰分析可以简化为单一串扰源的情况。接着从接收机检测光电流的概率分布函数出发 ,给出了单一串扰源的精确误码率表达式 ,串扰功率代价的分析结果与实验测量非常吻合。     

Impact of Fiber Non-linearity in High Capacity WDM Systems and in Cross-Connected Backbone Networks

The rapidly increasing data traffic volumes will demand for very high transmission capacity and network nodes throughput. Wavelength division multiplexing (WDM) technology will be asked to support many channels on the same fiber, both in point-to-point links and in WDM optical networks. The transmission of a high number of wavelength channels in all these systems is a key issue. This paper analyzes this topic, in both high capacity links and optical networks, highlighting the impact of fiber non-linearity, and addressing the main source of impairments. This is done through the use of a semi-analytical model recently upgraded to account for all the contributions deriving from Kerr effects, particularly four-wave mixing and cross-phase modulation. The analysis reveals that more than one hundred of channels at 2.5 Gbit/s can be transmitted in point-to-point links whose length can span until the order of 1000 km, and 32 channels per fiber, at the previous bit rate, can be handled in WDM networks, without dispersion compensation. For a higher number of channels (e.g., 64) dispersion compensation is needed.     

Performance evaluation of p-cycle based protection methods for provisioning of dynamic multicast sessions in mesh WDM networks

Network survivability is crucial to both unicast and multicast traffic. Up to now, extensive research has been done on unicast traffic protection. Recently, due to the rapid growth of multicast applications, such as video-conferencing, high definition television (HDTV), distance learning, and multi-player on-line gaming, the problem of multicast traffic protection has started to draw more research interests. The preconfigured protection cycle (p-cycle) method proposed by Grover offers fast speed in restoration (because p-cycles are pre-cross-connected) and high efficiency in resource utilization (because p-cycles protect both on-cycle and straddling links). So far p-cycles based protection approaches have been intensively studied for unicast traffic protection, but have been rarely investigated for multicast traffic. We propose to apply p-cycles to dynamic protection provisioning of multicast traffic, and evaluate the blocking performance in comparison to other existing multicast protection schemes. We consider three different p-cycle based multicasting protection methods, namely dynamic p-cycle (DpC) design, p-cycle based protected working capacity envelope (PWCE) design, and hybrid DpC and PWCE design. We show that p-cycle-based multicast protection approaches offer much better blocking performance, as compared with other existing multicast protection schemes. The main reasons for the much better blocking performance are attributed to the facts that (i) the selection of p-cycles is independent of the routing of the multicast light trees, (ii) there are no path/segment disjoint constraints between the selected p-cycles and the multicast light trees to be protected, (iii) the selected p-cycles are the most efficient p-cycles.

波分复用光网络的自愈方法分析

WDM (WavelengthDivisionMultiplexing ,波分复用 )系统的应用使得大容量的业务日益集中于同一系统内 ,这同时提高了对网络自愈性能的要求 ,从而导致各种自愈技术的发展。因为光器件具有高速交换的优点 ,因而从光层对业务恢复具有极大的优越性。文中主要分析了几种典型的光层的自愈方法     

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网络中的光层组播技术

组播应用主要是一些带宽密集型的业务,而光网络又能够提供巨大的带宽。随着光通信技术的发展,如何在光层实现组播已经成为光网络研究的热点之一。主要介绍了组播的应用以及在光层实现组播的关键技术;分析了实现光层组播的节点结构、光树的概念以及针对组播的波长路由算法。     

WDM光网络的研究进展

波分复用技术（WDM）在主干传送网应用越来越普遍,WDM网络技术的研究也获得了迅速发展,综述了当前主干WDM网络的最新研究进展和发展趋势。     

Probabilistic Analysis of Cyclic Packet Transmission Scheduling in WDM Optical Networks

We study the packet transmission scheduling problem with tuning delay in wavelength-division multiplexed (WDM) optical communication networks with tunable transmitters and fixed-tuned receivers. By treating the numbers of packets as random variables, we conduct probabilistic analysis of the average-case performance ratio for the cyclic packet transmission scheduling algorithm. Our numerical data as well as simulation results demonstrate that the average-case performance ratio of cyclic schedules is very close to one for reasonable system configurations and probability distributions of the numbers of packets. In particular, when the number of receivers that share a channel and/or the granularity of packet transmission are large, the average-case performance ratio approaches one. Better performance can be achieved by overlapping tuning delays with packet transmission. We derive a bound for the normalized tuning delay Δ such that tuning delay can be completely masked with high probability. Our study implies that by using currently available tunable optical transceivers, it is possible to build single-hop WDM networks that efficiently utilize all the wavelengths.     

Blocking Analysis of Dynamic Traffic Grooming in Mesh WDM Optical Networks

Traffic grooming in wavelength division multiplexing (WDM) optical networks routes and consolidates sub-wavelength connections onto lightpaths, to improve network utilization and reduce cost. It can be classified into static or dynamic, depending on whether the connections are given in advance or randomly arrive/depart. In this paper, an analytical model is developed for dynamic traffic grooming, allowing heterogeneous data rates for sub-wavelength connections, arbitrary alternate routing in both logical and physical topologies, and arbitrary wavelength conversion. The accuracy of the model has been verified by numerical results from simulation.     

机载多跳波分复用网络时间确定性分析方法

波分复用技术有望应用于航空电子系统的综合化互连,特别是传感器前端处理部分的实时网络互连。根据机载多跳波分复用网络的关键部件波长路由器的结构,对实时通信流量特性和优先级排队的服务特性进行建模,给出突发度、服务时延等参数指标的计算方法,并在高优先级时间触发流量的压力下,提出了在机载多跳波分复用网络中事件触发流量的最坏情况下,端到端延迟的网络演算方法;使用该方法计算得到的结果可以作为机载波分复用网络时间确定性分析的依据。将最坏情况下的分析结果与软件仿真结果相对比,发现两者变化规律相符,验证了该方法的有效性。     

波分复用网络的保护方式

首先介绍了在WDM网络中常用的光通道保护、光复用段保护方式及其实际使用方案,然后对WDM网络中采用不同保护方式的优缺点进行了分析,并对WDM网络中保护方案的设计提出了建议.     

Planning of WDM Ring Networks

The rapid introduction of wavelength division multiplexing (WDM) technology to cope with the increased bandwidth requirements of transmission networks has intensified the need for recovery mechanisms at the optical layer. A first step towards survivable optical networking will be seen through the introduction of optical rings. This paper presents different types of optical rings (dedicated and shared protection WDM rings) and the planning issues associated with these WDM rings. In particular, we give mathematical models as well as solution methods for the ring loading and wavelength assignment problem. We compare the wavelength requirement of dedicated and shared protection rings under scenarios with different demand patterns. We also discuss the influence of the WDM equipment cost, and present a mathematical model for the optimization of hybrid networks with both dedicated and shared protection rings.     

Capacity Efficiency and Restorability of Path Protection and Rerouting in WDM Networks Subject to Dual Failures

Resilient optical networks are predominately designed to protect against single failures of fiber links. But in larger networks, operators also see dual failures. As the capacity was planned for single failures, disconnections can occur by dual failures even if enough topological connectivity is provided. In our approach the design of the network minimizes the average loss caused by dual failures, while single failures are still fully survived. High dual failure restorability is the primary aim, capacity is optimized in a second step. For WDM networks with full wavelength conversion, we formulate mixed integer linear programming models for dedicated path protection, shared (backup) path protection, and path rerouting with and without stub-release. For larger problem instances in path rerouting, we propose two heuristics. Computational results indicate that the connectivity is of much more importance for high restorability values than the overall protection capacity. Shared protection has similar restorability levels as dedicated protection while the capacity is comparable to rerouting. Rerouting surpasses the protection mechanisms in restorability and comes close to 100% dual failure survivability. Compared to single failure planning, both shared path protection and rerouting need significantly more capacity in dual failure planning.     

Dynamic Routing in WDM Grooming Networks

Traffic grooming in optical networks has gained significant importance in recent years due to the prevailing sub-wavelength traffic requirement of end-users. In this paper, a methodology for dynamic routing of fractional-wavelength traffic in WDM grooming networks is developed. To evaluate the performance of routing algorithms, a new performance metric that reflects the network utilization is also proposed. The performances of shortest-widest path, widest-shortest path, and available shortest path routing algorithms are evaluated on a class of WDM grooming networks by considering traffic of different capacity requirements. The effect of dispersity routing, where higher capacity requests are broken into multiple unit capacity requests, is also investigated. The most interesting counter-intuitive result that is observed is that increasing the grooming capability in a network could result in degrading the performance of the widest-shortest path algorithm.     

WDM光网络中的业务疏导

目前WDM光网络普通用户大量的一般业务请求数目及波长通道带宽的不断增加极大的增加了网络中电层和光层设备的处理负担,增加了网络成本。对低速电信号复用到高速光通道进行优化,减少网络电层设备的使用,降低网络成本的业务疏导(TrafficGrooming)技术成为目前光网络研究的一个热点。本文主要介绍了WDM光网络中的业务疏导问题的基本概念、技术特点、国内外研究现状进行了总结。     

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。     

全光网中的波长变换器放置问题研究

波长变换器的出现可有效地提高WDM全光网的网络性能。文童对WDM全光网中的波长变换器放置问题进行了深入的研究,详细阐述了各种波长变换器放置算法的设计思想,并对各种算法的性能以及时间复杂度等参数进行了分析,并在典型拓扑上进行了仿真。     

Performance Analysis of WDM Optical Networks with Wavelength Usage Constraint

Due to power considerations, it is possible that not all wavelengths available in a fiber can be used at a given time. In this paper, an analytical model is proposed to evaluate the blocking performance of wavelength-routed optical networks with and without wavelength conversion where the usable wavelengths in a fiber is limited to a certain maximum number, referred to as wavelength usage constraint. The effect of the wavelength usage constraint is studied on ring and mesh-torus networks. It is shown that the analytical model closely approximates the simulation results. We also evaluate the performance of the first-fit wavelength assignment algorithm and compare its performance with the random wavelength assignment algorithm through simulation. It is observed that increasing the total number of wavelengths in a fiber is an attractive alternative to wavelength conversion when the number of usable wavelengths in a fiber is maintained the same.