全光网络中的光器件

21世纪将是“信息时代”,随着社会的发展,对通信的需求不断上升,通信技术也在突飞猛进的发展。信息的传输和交换正由电光网络向全光网络发展。全光网络以光纤为传输媒介,采用光波分复用(WDM)技术提高网络的传输容量。然而,WDM技术的进步主要依赖光器件的进步。     

全光网络中的MEMS光开关

介绍了目前国内外光纤通信系统中所涉及的电磁驱动移动式MEMS光开关、静电驱动式光开关、基于MEMS光大器的可扩展型光开关矩阵、喷墨气泡MEMS光开关、开环式1×N波长选择MEMS光开关。对这些器件的结构原理,制造方法及其性能指标作了分析。把这些器件的性能指标和当前光纤通信系统中的光开关的性能要求进行比较,分析了这些器件的应用前景。最后,对MEMS光开关做出了展望,指出了今后MEMS光开关的进一步研究方向。     

多波长全光网络

以波分复用 (WDM )技术为基础的多波长 (全 )光网络是当今光通信领域的研究热点。多波长全光网络的现场试验集中反映了与此有关各领域的研究水平和实用化进程。文章着重分析了有代表性的光网试验项目     

全光网络中的波长变换

虚波长通道是充分发挥 WDM光网络带宽资源的关键所在 ,而波长变换器又是实现虚波长通道的根本途径。本文在介绍目前重要的全光波长变换器的同时 ,对它们进行了全面的分类和比较。并对它们的优缺点进行了深入的分析。     

全光网络波长数优化设计

在 WDM全光网的波长数优化设计中 ,本文采用最长路径优先的波长分配策略对 Naohide Nagatsu等人提出的 WP优化方案进行了改进。改进后的方案比原 WP优化方案更加简洁 ,并且仍然能够达到原 WP优化方案的优化效果。     

全光波长转换器件开发现状

波长转换是实现光子网络(Photonic Network)中的灵活波长控制的关键技术之一。在光子网络的光互连节点上,波长转换技术的应用能够降低通道阻塞的概率,并能实现波长的重复使用。波长资源的有效利用也有利于促进灵活网络的构筑。全光波长转换(All-Optical WavelengthConversion)由于无需光电(OE)/电光(EO)转换器件,而且不受光信号格式(Signal Format)及位速率的限制,使得光子网络具有透明性,其自身也因此成为一项引人关注的技术。本文将扼要介绍一些有关全光波长转换器件的研发现状。一、光子网络中的波长转换技术波长转换器件的基本要求…     

全光网络及其关键技术和器件

简介全光网络的概念，概述实现全光网络的关键技术和器件。     

全光网络中的波长变换技术

1光网络中的波长变换技术在全光网络中,波分复用光交换是必不可少的,而波长变换则是实现波分复用光交换的关键技术之一。波长变换器(WavelengthConverter,WC)是解决全光网络中波长路由竞争的关键器件,是充分发挥WDM网络宽带资源的必要手段。波分复用光交换现用的波长变换器只能     

一种静电MEMS光开关的理论与实验研究

光开关是全光网络(All—Optical Network，AON)的一种基本器件。目前，制作光开关的方法有MEMS、波导、铁电液晶、Bubble、热毛细管、全息技术等。其中，MEMS光开关由于具有体积小、集成度高、能大规模生产等优点而成为光开关研究的热点之一。文章对一种静电驱动的光开关的设计进行了理论分析和仿真，并通过实验研究，证明了方案的可行性I同时，表明工艺技术是MEMS光开关研究成败的关键。     

自动交换光网络中全光波长转换器的应用和实现

作为自动交换光网络中的核心器件,全光波长转换器在网络中发挥着重要作用.总结了全光波长变换的实现方法,并重点介绍基于半导体光放大器交叉相位调制和利用可调谐光纤光栅外腔半导体激光器实现全光波长变换的最新进展、工作原理,最后简单介绍本实验室目前所做工作以及取得的成果.     

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.     

应用于分级复用系统的全光网波长分配算法

研究了全光网中采用分级复用系统的波长分配问题,充分考虑到分级复用系统在降低整个网络成本上的重要意义,以最小化光纤数量和波长路径为优化目标,提出一种启发式波长分配算法。     

Sparse Wavelength Conversion in Wavelength-Routed WDM Optical Networks*

A wavelength-routed optical network can suffer inefficiencies due to the wavelength-continuity constraint (under which a signal has to remain on the same wavelength from the source to the destination). In order to eliminate or reduce the effects of this constraint, a device called a wavelength converter may be utilized. Due to the high cost of these wavelength converters, many studies have attempted to determine the exact benefits of wavelength conversion. However, most of these studies have focused on optical networks that implement full wavelength conversion capabilities. An alternative to full wavelength conversion is to employ only a sparse number of wavelength converters throughout the network, thereby reducing network costs. This study will focus on different versions of sparse wavelength conversion--namely, sparse nodal conversion, sparse switch-output conversion, and sparse (or limited) range conversion--to determine if most of the benefits of full conversion can be obtained using only sparse conversion. Simulation and analytical results on these three different classes of sparse wavelength conversion will be presented. In addition, this study will present heuristic techniques for the placement of sparse conversion facilities within an optical network.     

Wavelength Conversion in WDM Optical Networks: Strategies and Algorithms for Limiting the Number of Converters in the Optical Cross-Connects

This paper considers the problem of wavelength conversion in optical networks using wavelength division multiplexing technique. In the previous literature, two main wavelength routing and assignment strategies have been introduced: wavelength path (WP) and virtual wavelength path (VWP), depending on whether the signal stays on the same wavelength or is converted to another during its travel throughout the network. While the former method does not require any wavelength conversion, the latter needs wavelength conversion in each optical node and, in particular, a wavelength converter per each signal handled by the node itself. From the previous literature emerged that the VWP leads to optical cross-connect (OXC) with lower dimensions compared to the ones required by the WP scheme, and that the difference between the WP and VWP schemes increases as the number of wavelengths carried by each fiber increases. In this paper a new strategy is introduced, named partial virtual wavelength path (PVWP), with the related wavelength routing and assignment algorithm, which makes limited use of wavelength conversion compared to the VWP scheme, and allows the same advantages of VWP to be attained with lower OXC dimensions. The paper reports a comparative analysis among the different strategies, considering both the cases of a network without failures and a network with the possibility of failure restoration. The main result is that the proposed PVWP strategy allows the same advantages of the VWP scheme with a strongly reduced number of wavelength converters (around 5% of the number required by VWP scheme). This figure does not vary appreciably if failure restoration is considered. The new strategy can be adopted by using an opportune OXC architecture, as illustrated in the paper, which allow a limited number of converters to be shared among all the channels as a common pool.     

全光通信网技术

本文对全光网的概念和关键技术做了简要说明，并介绍了具有代表性的全光网络，最后对各个网络的技术进行了比较，并同了全光网发展的一些主要障碍。     

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.     

基于Fabry-Perot结构的可调波长选择光开关

本文提出波长选择光开关的概念,首次研制出一个基于Fabry-Perot结构的可调波长选择光开关,该开关为2×2光纤端口,每个端口携带N个波长,工作时可以选1个或多个波长,插入损耗小于3dB,波长调谐范围10nm,调谐机构为一对多层三明治结构的压电陶瓷,具有驱动电压低,小于5V的驱动电压可以达到3.3nm的调谐,最大开关时间为1毫秒,开关比优于30dB.最后还分析了其基本透射与反射光谱性能,并讨论其对光通信、光交换网络产生的重要应用价值.