光时分复用技术及其实用价值

传统的电时分复用系统目前实验室里已经达到４０Ｇｂ／ｓ的水平,由于电子运动速率的极限,已经没有多少潜力可以挖掘了。解决这个问题的办法是用ＷＤＭ和ＯＴＤＭ（光时分复用）。ＷＤＭ技术比较成熟,且已经商用化。而ＯＴＤＭ尚处于实验研究阶段,这种技术克服了ＷＤＭ的一些缺点,如光放大器增益的不平坦,光纤的非线性限制等。ＷＤＭ的数据流在多个波长上传输,存在波长变换的问题,而ＯＴＤＭ则不存在这个问题,因此,ＩＰ ＯＶＥＲ ＯＴＤＭ比ＩＰ ＯＶＥＲＷＤＭ更优越,它可以在时域中对数据包直接进行处理。可以预测随着全光处理…     

通信知识

光时分复用ＯＴＤＭ光时分复用（ＯＴＤＭ：ＯｐｔｉｃａｌＴｉｍｅＤｉｖｉｓｉｏｎＭｕｌｔｉｐｌｅｘｉｎｇ）是在光频域范围内对光支路数据流进行复用的一种通信方式,可使光信号在光纤中实现超高比特率传输（如１００Ｇｂｉｔ／ｓ以上）,是光纤复用的最佳的途径。但目前ＯＴＤＭ仍局限在试验室内,有一些技术问题还没能得到深入的解决。例如ｐｓ脉冲的产生、复接／分接和同步,以及用ＯＴＤＭ实现超比特率传输所使用的非线性（孤波）传输（这种传输需要克服一些色散作用）等等。这些问题一旦得到解决,就会使ＯＴＤＭ技术趋向成熟…     

OTDM／OTDMA在SDV接入网中的应用

在光纤接入网中,为了提高传输容量、降低成本,充分实现光纤传输媒质和传输设备资源共享,在下行方向,采用多路信号可同时传输的复用技术;而上行方向,由于ＯＬＴ（光纤线路终端）需与多个位置不同的ＯＮＵ（光网络单元）相连,故采用可区分不同用户的多址技术。目前存在着多种复用技术和多址技术,如波分复用（ＷＤＭ）、码分复用（ＣＤＭ）、频分复用（ＦＤＭ）。光时分复用（ＯＴＤＭ）等复用技术,及波分多址（ＷＤＭＡ）、码分多址（ＣＤＭＡ）、光时分多址（ＯＴＤＭＡ）等多址技术。其中ＯＴＤＭ／ＯＴＤＭＡ以其较高的系统容量而…     

从cdmaOne到Cdma2000的无缝演进路径

在２０００年世界无线电大会上，第３代移动通信系统（３Ｇ）的地面系统被确定可使用５种无线传输技术，它们是ＣＤＭＡ－ＤＳ、ＣＤＭＡ－ＭＣ、ＣＤＭＡ－ＴＤＤ、ＴＤＭＡ－ＳＣ和ＴＤＭＡ－ＴＤＤ。其中前３种基于ＣＤＭＡ（码分多址）技术，后两种基于ＴＤＭＡ（时分多址）技术。可见，在３Ｇ标准中，ＣＤＭＡ是主流技术。ＣＤＭＡ（Ｃｏｄｅ Ｄｉｖｉｓｉｏｎ Ｍｕｌｔｉｐｌｅ Ａｃｃｅｓｓ）蜂窝系统由于采用了一种称之为扩频的通信技术，所以与采用ＴＤＭＡ和ＦＤＭＡ（频分多址）的ＧＳＭ蜂窝系统相比，具有抗干扰性好、系统容量…     

北电网络为浙江省网提供10Gbit/s传输产品

北电网络公司继今年１１月正式通过信息产业部专家组对其１０Ｇｂｉｔ／ｓ传输产品的联合测试后,近日又与浙江省邮电管理局签署了价值６００万美元的合同,根据合同,北电网络将为浙江省网提供１０Ｇｈｉｔ／ｓ产品。 浙江省省网干线项目中除了 １０Ｇｂｉｔ／ｓ ＴＤＭ设备外,还采用了北电网络的ＯＰＴｅｒａ ＬＨ产品,从而使浙江省成为中国大陆第一个应用该平台的用户。 ＯＰＴｅｒａ ＬＨ是一个独特的开放式平台,它既可以提供集成式ＤＷＤＭ系统,也可以提供与其他厂商ＳＤＨ设备兼容的波长转换器（ＯＴＵ）,以构成开放式的ＤＷＤＭ…     

一种计算多面体目标RCS的等效边缘电磁流公式

本文将Ａｏｄｏ计算平面目标物理光学（ＰＯ）场的等效边缘电磁流（ＰＯＥＥＣ）公式推广到能够计算复杂多面体目标的ＰＯ场，并对之修正，使该公式仅存在一个奇异点。这种ＰＯＥＥＣ和具有很少奇异点仅能计算边缘绕射场的等效边缘电流（ＰＴＤＥＥＣ）之和得到了能够计算散射总场且具有良好属性的ＧＴＤＥＥＣ。用导出的ＧＴＤＥＥＣ公式计算正方体和圆柱的双站ＲＣＳ，计算结果与实验和其它方法的结果吻合得到相当好，证实了ＧＴＤ     

信息站点2

朗讯科技ＴＤＭ１０Ｇｂｉｔ／ｓ系统在我国首次开通北京电信２０００年传输骨干网络扩容一期工程采用了朗讯科技的ＷａｖｅＳｔａｒＴＭＴＤＭ１０Ｇｂｉｔ／ｓ等先进的光网络设备 ,这是该系统首次在中国投入使用。北京电信在本地网中大规模引入１０Ｇｂｉｔ／ｓＳＤＨ设备 ,这在国内处于领先地位。北京电信２０００年传输网扩容二期工程也已决定采用朗讯科技的ＷａｖｅＳｔａｒＤＡＣＳ４／４／１,ＴＤＭ１０Ｇ（ＯＣ１９２） ,ＡＤＭ１６／１,ＡＤＭ４／１和ＩＴＭ -ＳＣ等设备。 (正 )爱立信推出针对ｃｄｍａ２０００的分组核心网解决方…     

WHB41型18～40GHz混频组件

ＷＨＢ４１型１８～４０ＧＨｚ混频组件南京电子器件研究所已研制成１８～４０ＧＨｚ下变频器组件。该组件由１８～４０ＧＨｚ宽带双平衡混频器，１６ＧＨｚＧａＡｓＦＥＴＤＲＯ（第１本振），４２ＧＨｚＧａＡｓＧｕｎｎＤＲＯ（第２本振）和１６～４２ＧＨＺ本振切换混...     

光时分复用技术

时分复用（ＯＴＤＭ）技术是实现超高速传输的很有交的技术。本文论述了ＯＴＤＭ的主要技术及其前景，通过对ＯＴＤＭ技术在点对点通信系统对网络系统中的应用介绍，提出了ＯＴＤＭ和ＷＤＭ的结合是将来网络发展的方向。     

采用正交Gold序列的TDD—SS—CDMA无绳电话系统性能

本文比较了ＳＳ－ＣＤＭＡ系统中的时分双工（ＴＤＤ）和频分双工（ＦＤＤ）技术，得出了在无绳电话系统中应采用时分双工（ＴＤＤ）方式的结论。在对正交Ｇｏｌｄ序列的性能分析的基础上，对采用ＴＤＤ方式的ＳＳ－ＣＤＭＡ无绳电话系统的正向链路信道和反向链路信道的误码性能及容量进行了分析。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.