WDM全光网络中一种分布式路由及波长分配协议

在全光网络中,光信号在全光域内传输,避免了光-电转换带来的延迟,因此全光网支持高数据率传输并提供巨大的网络容量。WDM(波分多路复用)技术的采用使得高速光传输线路与低速终端处理设备之间能够相互兼容。探讨了WDM全光网中的路由及波长分配问题,提出了一种用于WDM网络中的分布式路由及波长分配协议,具有开销小、阻塞率低以及良好的可扩展性,是一种比较实用的RWA协议。     

RWA方法对WDM网络P圈优化性能的影响

研究不同的路由和波长分配（RWA）方法对无波长变换WDM网络P圈优化性能的影响.提出了用负载均衡的方法对各波长层的工作容量进行均衡,以降低网络总容量.分别研究了动态分层通用RWA（DL-GRWA）、最短路径RWA（SP-RWA）、动态分层负载均衡（DL-LB）、最短路径负载均衡（SP-LB）、固定波长负载均衡（FW-LB）5种方法对网络总容量的影响.仿真发现,无论何种RWA方法,随着圈最大跳数限制的变大,网络总容量都逐渐降低,其中SP-LB方法所需要的网络总容量最小.     

基于节能的绿色光网络路由算法的研究

在传统的网络路由算法中,一般采用最短路径算法进行路由选路,最短路径算法以节点间的距离为权重,计算一条由源节点至目的节点的权重最小的路径以完成路由。最短路径算法虽然最小化了距离长度代价,却没有考虑能耗问题,所以使用最短路径算法所得出路径的能耗并不一定是最小的。针对这一问题,提出一种新型的综合性绿色路由算法,设定能耗作为节点间的权重,融合光旁路及业务量疏导,同时考虑路由和波长分配(RWA)问题,将完成每个业务所需要的能耗最小化,实现节能。仿真结果表明,与最短路径算法相比,绿色路由算法在较大规模网络中能够节省约40%的能耗,节能效果相当显著。     

多域光网络基于多核点共享树的多点对多点组播

针对多域光网络环境下传统的多点对多点(MP2MP)组播路由和波长分配(RWA)算法未考虑最优化组播域序列选择的问题,以及所导致的网络资源占用量过高和难以满足实时业务服务质量(Qo S)要求的问题,提出了一种面向多域光网络、计算可并行化、基于时延和最小代价约束的多核点共享树RWA启发式算法(MSTDC)。该算法通过构造虚拓扑的方式将多域的问题转化到单域中求解,从而实现了多核点共享树最小化核心点的个数及其所在域的准确计算。在多域间并行地将源和目的节点按照特定的Qo S选择策略和算法加入到不同的共享树中。仿真验证了在网络节点数为50个且均匀地分布在9个域内的多域光网络环境下,MSTDC算法与传统组播树算法相比波长资源占用率降低可达51.1%,路由成功率提高可达24.8%,算法执行时间降低可达64.6%。     

WDM波长路由光网络的波长分配算法

由于WDM网络中的传输和交换是以波长为粒度进行的。因此波长分配算法就成为光网络的研究热点。有效的算法可大大提高波长的利用率，并可充分挖掘WDM的带宽资源。介绍了WDM全光网络中静态和动态波长分配算法，尤其是结合大型网孔网络详述了几种动态波长分配算法。针对波长变换器在全光网络中的应用。提出了一种可以解决任意类型光网络的分层图算法，它可以一次性解决路由选择和波长分配问题，大大提高了该算法的效率。是未来光网络中非常有前景的一种波长分配算法。     

动态波长路由的全光连接建立时间的优化方法

本文描述了在波长路由光网络中影响连接建立时间的限制因素，提出了预置光路的方法，通过对路由和波长分配算法的改进减小部分连接的建立时间。模拟计算表明，优化的算法可以使部分连接有效地利用预置光路，从而减小连接建立时间，提高网络的整体性能。     

基于双通构型的和频、差频可变波长路由方案及其应用

提出了双通构型的基于“和频”和“差频”级联二阶非线性效应的可变波长路由方案,通过调节两个抽运源的频率,可以从一个WDM(wavelength division multiplexing)链路中取出任意一个信道,然后将其转换为任意一个波长并插入到另一个WDM链路中去.实现了可调谐波长转换和光波长路由的结合.通过小信号分析,给出了相位匹配情况下,输入信号光在波导中功率变化的表达式和输出转换光功率变化的表达式,并给出了提高系统效率的对两个抽运光功率的优化方案.数值计算表明,只要信道间隔大于02nm(25GHz 关键词： 光波长路由 光波长转换 光交换 PPLN     

基于双通构型的和频、差频可变波长路由方案及其应用

提出了双通构型的基于“和频”和“差频”级联二阶非线性效应的可变波长路由方案，通过调节两个抽运源的频率，可以从一个WDM(wavelength division multiplexing)链路中取出任意一个信道，然后将其转换为任意一个波长并插入到另一个WDM链路中去.实现了可调谐波长转换和光波长路由的结合.通过小信号分析，给出了相位匹配情况下，输入信号光在波导中功率变化的表达式和输出转换光功率变化的表达式，并给出了提高系统效率的对两个抽运光功率的优化方案.数值计算表明，只要信道间隔大于02nm(25GHz     

基于光纤四波混频效应的新型组播方法

组播是波长路由光通信网络中的一项重要功能.提出并实验实现了基于高非线性光纤四波混频效应的全光组播方法,将一束载有数据的输入信号光和一束抽运光一起入射到一段高非线性光纤中,通过两个简并四波混频过程产生了两个携带该数据信息的闲频光,从而实现了单一信号的两信道组播,同时抽运光也会受到数据信息的调制.该方法的优点在于组播的实现只需要单一的抽运光源,而不需要再提供其他输入光,结构简单,组播光信号功率均匀、波长可调,并且具有进一步增加组播信道的能力. 关键词： 组播 四波混频 高非线性光纤     

基于光注入Fabry-Perot半导体激光器实现同步全光分路时钟提取与波长转换

提出了一种利用Fabry-Perot（FP）半导体激光器同步提取波长转换的分路光时钟的新方法,并对该方法进行了数值模拟和实验验证.光注入半导体激光器会产生非线性单周期振荡特性,利用交叉增益调制效应及对单周期振荡的微波锁频效应,可从光时分复用信号中提取出波长转换的分路光时钟.采用一个FP半导体激光器作为全光分路时钟提取及波长转换器,数值模拟实现了从波长为1555 nm、速率为2×20 Gb/s的光时分复用信号中提取出波长转换为1550 nm、重复频率为20 GHz的分路光时钟,实验完成了从波长为155024 nm、重复频率为1236 GHz光脉冲信号中提取出相位噪声为-105 dBc/Hz的波长为154591 nm、重复频率618 GHz的分频光时钟.此外还详细研究了注入光功率、波长失谐、FP激光器偏置电流及纵模选择对光时钟提取的影响,实验结果和数值模拟结果符合.该方法在光时分复用混合波分复用通信系统中实现全光解复用及波长路由有着重要的应用价值. 关键词： 波长转换 时钟提取 光注入 非线性动力学     

LC-DLA: A fair congestion-aware Distributed Lightpath Allocation mechanism

One of the main challenges in all-optical WDM networks is the problem of Routing and Wavelength Assignment (RWA). In large-scale networks with heavy traffic load, distributed RWA is more suitable than centralized RWA. One of the distributed algorithms proposed recently is Distributed Lightpath Allocation (DLA) [1]. We use the DLA as our basic algorithm to design a new congestion-aware RWA algorithm, called Least-Congested Distributed Lightpath Allocation (LC-DLA). We consider congestion in the network as a decision point for solving RWA. Selection of the least congested path among available paths from source to destination can improve the blocking probability of the network. Fairness is one of the crucial metrics that network designers should consider. We define a new concept for fairness in RWA. Our performance evaluations show that LC-DLA can provide good blocking and fairness performances in WDM networks.     

Optical bistabilities of higher harmonics: Inhomogeneous and transverse effects

The steady state behavior of optical bistable system in a ring cavity with transverse field variations and inhomogeneousely broadened two-level atoms is investigated outside the rotating wave approximation (RWA). Analytical and numerical investigation is presented for different cases of transverse field variations with Lorentzian or Gaussian line widths. When both (transverse and inhomogeneous) features taken into account, the first harmonic output field component outside the RWA exhibits a one-way switching down processes (butterfly OB) or reversed (clockwise) OB behavior, depending on the atomic linewidth shape.     

Nature-Inspired Routing and Wavelength Assignment Algorithms for Optical Circuit-Switched Polymorphic Networks

Polymorphic optical networks simultaneously support several optical switching paradigms over a single physical network. In this way, they provide service differentiation at the optical layer by employing the most appropriate paradigm for each service. One type of such architecture is the optical circuit-switched polymorphic network (OCSPN), which combines optical circuit switching paradigms with different grades of dynamism. The performance of this network relies on the utilization of efficient routing and wavelength assignment (RWA) algorithms. In this article, we review the fundamentals of OCSPNs and present a set of efficient RWA algorithms based on ant colony optimization and genetic algorithms.     

Nature-Inspired Routing and Wavelength Assignment Algorithms for Optical Circuit-Switched Polymorphic Networks

Polymorphic optical networks simultaneously support several optical switching paradigms over a single physical network. In this way, they provide service differentiation at the optical layer by employing the most appropriate paradigm for each service. One type of such architecture is the optical circuit-switched polymorphic network (OCSPN), which combines optical circuit switching paradigms with different grades of dynamism. The performance of this network relies on the utilization of efficient routing and wavelength assignment (RWA) algorithms. In this article, we review the fundamentals of OCSPNs and present a set of efficient RWA algorithms based on ant colony optimization and genetic algorithms.     

Analytical formulas for calculating the blocking probability of a dynamic star network

For a dynamic routing and wavelength assignment (RWA) a star topology is shown to be more efficient in comparison with a ring topology. Analytical formulas for a dynamic RWA in a star network are presented and verified with virtual simulation.     

A New RWA Algorithm Based on Multi-Objective

In this article , we studied the associated research problems and challenges on routing and wavelength assignment (RWA) in WDM (wavelength division multiplexing) networks. Various RWA approaches are examined and compared.We proposed a new RWA algorithm based on multi-objective. In this new algorithm, we consider multiple network optimizing objectives to setup a lightpath with maximize profit and shortest path under the limited resources. By comparing and analyzing, the pro posed algorithm is much better than the algorithms, which only consider one optimizing objective.     

Routing and wavelength assignment in WDM networks with dynamic link weight assignment

We consider the routing and wavelength assignment problem on wavelength division multiplexing networks without wavelength conversion. When the physical network and required connections are given, routing and wavelength assignment (RWA) is the problem to select a suitable path and wavelength among the many possible choices for each connection such that no two paths using the same wavelength pass through the same link. In wavelength division multiplexing (WDM) optical networks, there is need to maximize the number of connections established and to minimize the blocking probability using limited resources. In this paper, we have proposed three dynamic link weight assignment strategies that change the link weight according to the traffic. The performance of the existing trend and the proposed strategies is shown in terms of blocking probability. The simulation results show that all the proposed strategies perform better than the existing trend.     

Optical bistability without the rotating wave approximation

Optical bistability for two-level atomic system in a ring cavity is investigated outside the rotating wave approximation (RWA) using non-autonomous Maxwell-Bloch equations with Fourier decomposition up to first harmonic. The first harmonic output field component exhibits reversed or closed loop bistability simultaneously with the usual (anti-clockwise) bistability in the fundamental field component.     

薛定谔猫态光场与二能级原子相互作用系统的量子特性

在非旋波近似下,通过采用相干态正交化展开的方法,研究了薛定谔猫态光场与二能级原子相互作用系统中,原子的布局数和光场的反聚束效应,并与旋波近似下的结果进行了对比.在旋波近似与非旋波近似下,讨论了初始光场强度、相干态间的相位角以及失谐量对原子布局数和光场反聚束效应的影响;在非旋波近似下,讨论了强弱耦合情况下光场的反聚束效应.研究结果表明:旋波近似与非旋波近似下,原子的布局数随着初始光场强度的不同,表现出不同的特性;当初始光场强度较小时,旋波近似与非旋波近似下,原子的布局数表现出相同的特性;随着初始光场强度的增大,旋波近似下,原子的布局数将表现出坍塌现象.耦合强度较大时,光场的聚束与反聚束效应在非旋波近似与旋波近似下有较大的区别;非旋波近似下,随着初始光场强度的增大,光场一直处于聚束效应状态;而旋波近似下,光场的聚束效应与反聚束效应交替出现.