多光纤WDM网中支持QoS的波长重路由算法

在WDM网上，波长连续性限制会降低网络的信道利用率，增加光路建立请求的阻塞率。采用波长重路由技术可以减少波长连续性限制对网络性能的影响。该文采用波长图模型，对多光纤WDM网中支持QoS的波长重路由算法进行了探讨，提出一种支持QoS的波长重路由算法－－动态选择法，并采用两种网络模型，在不同负载的动态业务下对所提算法进行了仿真研究；仿真结果表明所提算法既满足了上层业务不同的QoS要求，同时又充分利用了有限的网络资源，使全网的平均阻塞率降低。     

WDM网络中稀疏多纤及波长配置算法

由于成本及技术的原因, WDM光网络中的波长变换设备资源和单纤波长数有限,但在网络 建设时,会预留富裕的光纤,如何依据动态业务有效利用这些光纤降低网络阻塞率,并优化单纤波长配置以 满足网络性能,具有现实意义。该文提出了一种WDM网络的稀疏多纤及波长配置算法,该算法基于动态 业务。仿真结果表明,利用稀疏多纤的网络配置,只需要较少的单纤波长即可满足网络阻塞性能要求。     

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。     

几种新型多波长光纤激光器

综合报道几种新型多波长光纤激光器 ,并对这些激光器的机理、实验装置和研究结果进行了详细介绍 ,对今后多波长激光器的发展方向作一展望。     

多波长掺铒光纤激光器的研究进展

综合报道了几种新型多波长掺铒光纤激光器,并对这些激光器的机理、实验装置及结果进行了详细的介绍,并展望多波长掺铒光纤激光器的发展方向。     

可调谐多波长掺铒光纤激光器

近年来,多波长光纤激光器作为密集波分复用系统中的重要光源而被广泛研究.对多信道取样光纤光栅(M-FBG)进行了详细的理论分析,并在此基础上实现了一种可调谐多波长光纤激光器.该激光器采用环形腔结构,以掺铒光纤作为增益介质,利用M-FBG的多波长选择特性在室温下实现了功率平坦度小于1dB、3dB线宽小于0.1nm、边模抑制...     

多波长掺铒光纤激光器的研究进展

概述了用于密集波分复用通信的多波长掺铒光纤激光器(MW-EDFL)的研究进展，介绍了实现多波长激光输出的多种方法，并对其原理、实验装置和研究结果进行了详细阐述和分析，展望了多波长激光器的发展方向．     

总线形与环形全光网中波长转换器的配置算法研究

波长转换技术可以消除全光网络中的波长一致性限制,降低网络阻塞率,因而在数量有限时存在合理配置、使用波长转换器的问题,本文在推导、分析网络阻塞率的基础上,提出了一种用于总线形和环形全光网的波长转换器配置算法,并对该算法进行了计算机模拟。模拟结果表明本算法的配置结果得出的网络阻塞率与最佳配置时的非常接近,而本算法的时间复杂度仅为O（4H＋2w)。     

多波长超辐射光纤光源的研制

研制了采用 980 nm激光泵浦双程反向结构 Er+ 3 掺杂辐射光纤光源。该结构与反射式光纤光栅滤波器相结合 ,获得了稳定波长输出线宽窄的多波长光纤光源     

基于反馈光纤环的可调多波长布里渊掺铒光纤激光器

提出一种基于反馈光纤环(FFL)的多波长布里渊掺铒光纤激光器(MW-BEFL)。主腔由光环形器构成单通谐振腔,长度为50m,而FFL选用传统单纵模布里渊光纤激光器的光纤,长度为10m,以保证每一阶斯托克斯波及反斯托克斯波处于单纵模运行状态,并添加恒温系统消除外界干扰。采用延时干涉法,测得第一阶斯托克斯有45dB的边模抑制比和3.23kHz的线宽,通过调节不同的掺铒光纤放大器(EDFA)功率,对比分析了每一阶斯托克斯波和反斯托克斯波的关系。利用级联受激布里渊散射和四波混频效应,最终获得了50nm(1520~1570nm)可调范围的间隔为0.084nm的15个稳定输出的多波长布里渊掺铒光纤激光器。     

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.     

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.     

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.     

波长变换器均匀放置的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放置时在阻塞率、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放置在链路负荷均匀的情况下的Mesh Torus中是一种优化配置     

基于稀疏约束最优化的ISAR相位自聚焦成像算法

本文提出了一种基于稀疏约束的ISAR方位自聚焦算法,能够应用于稀疏孔径ISAR成像中。该算法利用ISAR图像的稀疏特征建立最小1范数成像模型,并将相位误差作为模型误差。然后通过数值迭代的方式进行自适应相位误差估计,最终获得聚焦良好的ISAR图像。同时,成像代价函数的建立基于矩阵模型,有利于采用方位FFT和矩阵的Hardmard乘积操作进行快速求解。由于利用稀疏约束,该方法在低信噪比的条件下仍然能够取得良好的聚焦结果。基于仿真数据和实测数据的结果验证了本文算法的有效性。     

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.     

一种基于稀疏约束的稳健波束形成方法

通过分析最优自适应波束形成权矢量的子空间组成,发现最优权仅位于低维的干扰加信号子空间中.一般系统所要抑制的干扰数目远小于系统自由度,因此一旦估计出干扰空间和信号导向矢量,只需求解一个低维的组合矢量即可求得自适应权矢量,同时也极大地降低了计算复杂度.本文首先构造一个完备的干扰加信号子空间（IPSS）,然后对组合矢量进行稀疏约束,找到一组列数最小的信号加干扰子空间来构造自适应权.仿真实验验证了所提算法的有效性和稳健性.     

Routing and Wavelength Assignment in Optical Networks Using Logical Link Representation and Efficient Bitwise Computation

In this paper, we propose and evaluate a new approach for implementing efficient routing and wavelength assignment (RWA) in wavelength division multiplexing (WDM) optical networks. In our method, the state of a fiber is given by the set of free wavelengths in this fiber and is efficiently represented as a compact bitmap. The state of a multiple-fiber link is also represented by a compact bitmap computed as the logical union of the individual bitmaps of the fibers in this link. Likewise, the state of a lightpath is represented by a similar bitmap computed as the logical intersection of the individual bitmaps of the links in this path. The count of the number of 1-valued bits in the bitmap of the route from source to destination is used as the primary reward function in route selection. A modified Dijkstra algorithm is developed for dynamic routing based on the bitmap representation. The algorithm uses bitwise logical operations and is quite efficient. A first-fit channel assignment algorithm is developed using a simple computation on the bitmap of the selected route. The resulting bitwise routing algorithm combines the benefits of least loaded routing algorithms and shortest path routing algorithms. Our extensive simulation tests have shown that the bitwise RWA approach has small storage overhead, is computationally fast, and reduces the network-wide blocking probability. The blocking performance of our RWA method compares very favorably with three routing methods: fixed alternate routing, shortest path using flooding, and Dijkstra’s algorithm using mathematical operations. Our simulation experiments have also evaluated the performance gain obtained when the network access stations are equipped with finite buffers to temporarily hold blocked connection requests.     

梯度稀疏和最小平方约束下的低照度图像分解及细节增强

低照度图像存在细节模糊、对比度低等问题.针对这些问题,本文提出一种低照度彩色图像增强算法.首先建立梯度稀疏和最小平方约束模型,将图像分解为结构层和细节层;然后采用提出的多尺度边缘保护细节增强算法强化图像的细节信息并滤波;最后把细节增强的图像经改进的Retinex算法映射,最终得到细节增强、亮度适宜、对比度较强的修复图像.实验结果表明,主观上：图像细节增强,亮度适宜;客观上：结构层图像的一维像素线性图显示其平滑特性效果较好,细节增强图的NIQE（5.5202）、BRISQE（31.1893）和PSNR（25.3625）特征较好,修复图像的熵值（7.4421）、边缘强度（128.3231）和平均亮度（121.1827）较好.本文算法实现了对低照度图像的有效分解及细节增强,并提高了图像综合质量.     

一种低成本智能全光波长交叉交换连接器的设计和实现

报道了一种采用多个4×4,一个8×8光开关以及固定波长转换器组成的大容量全光波长交叉交换连接器(OWXC)的新颖结构,可以实现低串扰、低延迟的无阻塞光信号交换和转换,降低成本30%左右。同时,提出了应用于该结构的智能控制信号传输帧结构以及通过设置可用波长被锁定的时间门限来实现三种具有服务等级的智能光链路建立方式。实验结果显示,一条光链路从被断开到自动重新建立的时间是22 ms,可以实现人工、自动和半自动三种链路建立方式以及三根光纤,24个波长的全无阻塞交换,交换容量达到960 Gb/s。对组建大容量的光交叉连接(OXC)具有参考意义。