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1、光电子存储材料和技术许立新光存储 v光存储最早的形式是缩微照相：文档资料长期保存 的主要形式。将文献摄影，存放于缩微胶片上，缩 微胶卷、缩微教胶片、缩微卡片等。v激光全息：实现三维图像存储不能进行实时数据存 取。v光盘技术：光盘存储技术是本世纪70年代开拓出来 的。光盘存储集成系统中，光盘机和光盘片是核心 器件。在光盘机中光学读、写头是关键元件。 光盘存储器（简称“光盘”）是利用激光原理存储和读 取信息的媒介。光盘片用塑料制成，塑料中间夹入了一层薄 而平整的铝膜，通过铝膜上极细微的凹坑记录信息。只读光盘：信息是光盘制作时在盘面上一次性形成的，只能 读出 使用，不能重新写入。工厂通过压制方法生产
2、光盘时， 将信息以凹坑形式生成在铝膜上，成为永久的信息记录。一 片普通5”只读光盘可以存放650MB的信息。只读光盘是一种 非常好的可以长期保存的存储介质，今天许多商品软件和信 息资料都被制成光盘销售。刻录光盘：数据一旦进入光盘，所占的空间是不能释放的。可读写光盘：也已投放市场。光盘的结构特点和工作原理光盘和工作原理光盘表面：0/1光盘外观光盘工作原理激光束撞击 光盘表面凹坑平面棱镜反射 激光束激光二极管感光 二极管聚焦光脉冲转 换为0/1偶氮光存储基本原理光烧孔：光物理烧孔、光化学烧孔电子俘获It is estimated that the human race has created ab
3、out 1 exabyte (1018) of information to date. It is also predictedthat the next exabyte could be generated within the next three years. This unprecedented growth in information poses a number of significant challenges in terms of information storage, transmission, networking, and access. Storage serv
4、ices are currently growing at 120 percent a Year and are directly linked to the growth in geographically geographically dispersed online activities. Organizations are rapidly realizing that their central data storage facilities are called on by employees not only in the metropolitan area, but worldw
5、ide.Optical networks, however, have not been developed and optimized with data storage in mind, although it is now realized that they represent the main solution availabletoday for networking geographically dispersed storage and users.Fabric attached storage, which includes storage area networks (SA
6、Ns) and network attached storage (NAS), represents one of the fastest growing areas ofnetworking.Its goals include providing timely access to information, large capacity, dynamic reconfigurable behavior, data protectionand restoration, as well as covering a large Geographic coverage. SANs can offer
7、unique advantages, including consolidated storage with cost savings and reconfigurability, greater utility of centralized/distributed data, and data protection through replication for disaster recovery.This feature topic provides an overview of optical storage area networks.considers next-generation
8、 optical storage area networks based on the light-trails approach to dynamic wavelength provisioning. It discusses SAN extensions based on light-trails and pays attention to Disaster recovery and grid computing in the context of SANs. evaluates the reliability and availability of SAN extension solut
9、ions including IPbased extensions and Fibre Channel (FC)-based extensions.considers dispersion compensation for SANs where data centers still use legacy multimode fiber with a limited bandwidth-distance product. The article discusses the use of enhanced Bandwidth multimode fiber, electronic dispersi
10、on compensation, and the use of wavelength tuning control loops.addresses reconfigurable free-space optical switches for SANs. It introduces a holographic beam steering optical switch and shutter-based optical switches, and pays attention to optical packet switching for SANs. It is hoped that this f
11、eature topic presents a balanced view of developments in industry and academia in this rapidly developing field.The vast explosion of data traffic and the growing dependence of the financial world on electronic services have led to a tremendous incentive for SAN services and storage-capable networks
12、. Coupled with a need to store information and Dynamically reproduce it in real time, SANs are experiencing a new upward thrust. Local SANs based on the intra-office client-server hub- and-spoke model have long been deployed as the de facto standard for backing up servers and high-end computing devi
13、ces within campuses and premises. Next-Generation Optical Storage Area Networks: The Light-Trails Approachwith the growth of the Internet, back office operations, and a need for secure backup at geographically diverse locations, SANs have moved from their premises confinement to a larger area of pro
14、liferation. These new categories of SAN sites, also known as Internet data centers (IDCs), are becoming increasingly Important from the revenue as well as security perspectives.These sites are connected to one another and to their client nodes through a transport medium.Considering the high volume o
15、f data that is transferred between clients and servers today, transport is likely to take place across optical communication links. Optical fiber offers large bandwidth for high-volume transfer with good reliability to facilitate synchronous backup capabilities between SAN sites and clients or betwe
16、en multiple SAN sites in server mirroring operations. Currently, optical channels are used only for transport of information, while standardized protocols such as Fibre Channel, ESCON, and FICON operate at the data layer, enabling actual transfer of information.With the sharp rise in the need for dynamic services, future SAN systems should be able to cater to dynamic provisioning of “connections” between server sites and clients. Bandw
