波长变换器均匀旋转的Mesh—Torus的性能分析

本文主要研究了在WDM的Mesh-Torus中,部分网络节点使用波长转换器能给网络带来的好处。文中比较了在非泊松业务下,波长转换器按二项式分布和均匀分布旋转时在阻塞率、转换增益和公平性方面能带来的好处,证明了波长转换器均匀旋转在链路负荷均匀的情况下的Mesh-Torus中是一种优化配置。     

波长变换对光网络中阻塞性能的影响

在网状光网络中建立稀疏波长变换模型,定性的计算了有和没有波长转换器网络的阻塞概率。研究了在这两种网络中通道长度对阻塞概率的影响,以及波长转换器对提高网状光网络的阻塞性能的影响。建模结果表明,对大容量的网状网,波长变换器能大大降低网络的阻塞概率,但对一个波长数目不定且业务量接近饱和的网络作用不大。     

基于PVWP的有限波长转换的Mesh—torus网络的性能分析

本文主要探讨了Mesh-torus网络中,部分网络节点使用有限波长转换技术给网络性能带来的影响。我们比较了在非泊松业务模型下,有限波长转换和全波长转换在阻塞率、转换增益和公平性方面的性能,发现基于PVWP方案时网络节点只需具有转换度为d=3的波长转换能力就能达到全波长转换的性能。因此,通过将PVWP和有限波长转换技术结合来降低网络成本是可行的。     

WDM网络中波长转换稀疏性与有限波长转换能力的研究

阐述稀疏波长转换和有限波长转换技术的概念,讨论了这两种技术对网络阻塞率和波长转换增益的影响,并给出了一种用于波长和波长转换器分配的启发式算法。     

XGM波长变换器网络的路由波长分配算法研究

交叉增益调制(XGM,Cross-Gain Modulation),用于波长变换技术,可较简单地制成全光波长变换器。该文先用一个简单的近似模型分析了XGM波长变换器对路径阻塞率的影响,进而根据其本身固有的特点,设计了3种适合于XGM波长变换器网络的路由波长分配算法。通过在美国科学基金会骨干网络(NSFNET,National Science Foundation backbone network),和网孔型(Mesh-torus)网络中的仿真,从网络的阻塞率和公平性两个方面研究XGM波长变换器对网络性能的影响,同时比较了3种算法的性能。仿真结果表明,XGM波长变换器较无波长变换,可以在网络的阻塞率和公平性两个方面都得到较大的改善;3种算法中,FF/lowest算法在改善网络的阻塞率和公平性两个方面都是最优的。     

光开关大小对光网络阻塞概率的影响

引入一种基于电路交换WDM光网络的业务模型，推导出波长连续光网络和波长可转换光网络中阻塞概率关于光开关大小的公式．通过波长转换器的增益定性分析了光开关大小对这两种网络阻塞概率的影响，并用Matlab仿真验证．结果表明：光开关大小对网络(尤其是波长连续网络)有着很大的影响，但比起通道长度来其影响相对较小，网络的拓扑设计中需同时考虑这两者．     

稀疏波长变换网络性能分析与研究

文章对动态业务模型下的稀疏波长变换网络性能进行了分析与研究，对波分复用（WDM）网络中引入波长变换器后的网络性能进行了系统的仿真，分析了波长变换器数量、波长变换器位置、波长变换范围以及路由波长算法等因素对网络性能的影响。     

XGM波长变换器网络的性能分析

目前对有限范围波长变换器的研究或者是针对能变换到较长和较短波长的FWM(SOA(Semiconductor Optical Amplifier) in Four-Wave Mixing,基于半导体光放大器的四波混合)波长变换器的,或者是针对具有卷绕(Wraprounds)功能的变换器.本文研究了只具有单边变换且不具有卷绕的XGM(SOA(Semiconductor Optical Amplifier) in Cross-Gain Modulation,基于半导体光放大器的交叉增益调制)有限范围波长变换器对网络性能的影响,从网络的阻塞率方面比较了FWM与XGM波长变换器对网络性能的影响.研究结果表明,XGM波长变换器的性能虽然只相当于具有10-20%左右变换范围的FWM波长变换器,但较无波长变换器网络的性能已经有了较大的改善,同时与全范围波长变换器网络的性能相差并不太远.     

波长路由WDM网络中"稀疏-部分"波长转换的建模与分析

分析稀疏-部分波长转换网络的结构,论证了该结构在获得优秀的阻塞性能同时,能显著地节省波长转换器的数目.     

一种全光波长路由器的设计及性能分析研究

该文基于一种简单低成本的、波长转换节点共享型全光波长路由器结构,设计了以排队理论为基础的M/M/T/T模型,研究了波长路由器在波分复用波长路由网络中的阻塞特性。数值结果表明,全光网波长路由器的阻塞特性与复用波长数目,链路波长利用率,节点接入光纤端口数,有无波长转换器密切相关。尤其在受限波长转换条件下的配置优化分析,可看出波长路由器无需可调谐器件,也能获得灵活的波长转换能力,不但可避免波长路由器因为精确调谐所开销的时间,而且所有的控制均为简单的开关控制,可降低工程实现的复杂度。     

Performance Analysis of Multi-Fiber WDM Network with Limited-Range Wavelength Conversion

Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength conversion technology and wavelength converters play an important role in enhancing fiber utilization and in reducing the overall call blocking probability of the network. In this paper, we develop a new analytical model to calculate the average blocking probability in multi-fiber link networks using limited range wavelength conversion. Based on the results obtained, we conclude that the proposed analytical model is simple and yet can effectively analyze the impact of wavelength conversion ranges and number of fibers on network performance. Also a new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored. Finally, we analyze network performance with the proposed scheme. It can be observed from numerical simulations that limited range converters placed at a few nodes can provide almost the same blocking probability as full range wavelength converters placed at all the nodes. We also show that being equipped with a multi-fiber per-link has the same effect as being equipped with the capability of limited range wavelength conversion. So a multi-fiber per-link network using limited range wavelength conversion has similar blocking performance as a full wavelength convertible network. Since a multi-fiber network using limited range wavelength conversion could use fewer converters than a single-fiber network using limited range wavelength conversion and because wavelength converters are today more expensive than fiber equipment, a multi-fiber network in condition with limited range wavelength conversion is less costly than a single fiber network using only limited range wavelength conversion. Thus, multi-fiber per-link network using limited range wavelength conversion is currently a more practical method for all optical WDM networks. Simulation studies carried out on a 14-node NSFNET, a 10-node CERNET (China Education and Research Network), and a 9-node regular mesh network validate the analysis.     

波分复用波长路由节点的阻塞特性分析

利用概率统计理论的方法，从节点层次上定量分析了节点规模、复用波长数目以及波长转换对波分复用(WDM)波长路由网络中波长路由节点的影响。提出了基于概率统计的节点阻塞模型。数值结果突出表明波长转换能力越强的全光节点，其性能越优。为了提高网络资源的使用效率并增强全光网络的灵活性，必须实现全光网络中的虚波长路由波长转换器。通过数值计算找到了阻塞性能和代价的折中，研究中发现配置较低波长转换能力波长转换器的波长路由节点将会具备更强的性价比优势，当前在构建光通信系统时使用弱波长转换能力的光节点更可行。     

利用SOA交叉增益调制实现2.5 Gbit/s非归零码的全光波长变换

采用半导体光放大器 (SOA)的交叉增益调制进行了 2 5Gbit/s的非归零码光脉冲的波长变换。向下波长变换间距大于 2 0nm ,向上波长变换间距大于 10nm。对变换信号测量了接收机入纤功率和误码率的关系。实验中采用同向变换的方式 ,信号光中心波长固定 ,探测光采用外腔半导体激光器 ,中心波长连续可调。对变换信号进行了至少 1h的测量 ,误码为零。为其在波分复用(WDM)网络中的应用奠定了基础。     

A Comparison of Allocation Policies in Wavelength Routing Networks*

We consider wavelength routing networks with and without wavelength converters, and several wavelength allocation policies. Through numerical and simulation results we obtain upper and lower bounds on the blocking probabilities for two wavelength allocation policies that are most likely to be used in practice, namely, most-used and first-fit allocation. These bounds are the blocking probabilities obtained by the random wavelength allocation policy with either no converters or with converters at all nodes of the network. Furthermore, we demonstrate that using the most-used or first-fit policies gives an improvement on call blocking probabilities that is equivalent to employing converters at a number of nodes in a network with the random allocation policy. These results have been obtained for a wide range of loads for both single-path and general mesh topology networks. The main conclusion of our work is that the gains obtained by employing specialized and expensive hardware (namely, wavelength converters) can be realized cost-effectively by making more intelligent choices in software (namely, the wavelength allocation policy).     

Wavelength Conversion Placement in WDM Mesh Optical Networks*

Wavelength conversion helps improve the performance of wavelength division multiplexed (WDM) optical networks that employ wavelength routing. In this paper, we address the problem of optimally placing a limited number of wavelength converters in mesh topologies. Two objective functions, namely, minimizing the average blocking probability and minimizing the maximum blocking probability over all routes, are considered. In the first part of the paper, we extend an earlier analytical model to compute the blocking probability on an arbitrary route in a mesh topology, given the traffic and locations of converters. We then propose heuristic algorithms to place wavelength converters, and evaluate the performance of the proposed heuristics using the analytical model. Results suggest that simple heuristics are sufficient to give near-optimal performance.     

混合光波长转换在波分复用光网络中的应用

在全光网络中，如何合理利用波长转换来降低光网络的阻塞率是一个非常关键的问题。研究了最新的波长转换体系结构和波长转换手段，提出一种全新的混合波长转换方法，在减少网络中波长转换器个数的同时，维持拥塞概率类似于全波长转换。提出了5种不同的波长转换器使用策略，并利用数值模拟的方法，比较了这5种不同的波长转换器使用策略，分析结果，得出了最小化光网络的阻塞概率的波长转换使用策略。结合混合波长转换和波长转换器使用策略，进一步提出了光网络中优化波长转换器配置的遗传算法，通过对14个节点的美国自然科学基金网(NSF Net)的数值模拟，结果表明它是十分有效的，在减少光网络中波长转换器数量，且不增加光网络波长数量的情况下，基本保持原有网络性能。     

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.