Modulation and free-space link characteristics of monolithicallyintegrated vertical-cavity lasers and photodetectors with microlenses

We present temperature, modulation, and free-space link characteristics of monolithically integrated vertical-cavity lasers (VCLs) and resonant photodetectors. The devices have been integrated using a novel structure that makes it possible to fabricate devices with through-the-substrate emission and detection. Taking advantage of the substrate emitting/detecting architecture, we monolithically integrate microlenses on the substrate side of the devices and flip-chip bond arrays without via processes or substrate removal. Low-threshold high-efficiency VCLs exhibit maximum small-signal modulation bandwidths, which are limited by parasitics, of ~9.5 GHz at 20°C and ~8.4 GHz at 70°C. The VCLs have the lowest reported bias currents required to reach bandwidths of up to ~8 GHz. A free-space optical link is demonstrated with flip-chip-bonded arrays of microlensed, monolithically integrated VCLs and detectors. The link is found to be tolerant to temperature differences of ±75°C between the VCL and detector, with error free (BER<10^-12) data transmission demonstrated in each case     

A prototype flexible robot arm-an interdisciplinary undergraduateproject

An interdisciplinary undergraduate project to set up a prototype flexible robot link is discussed. The project consists of modeling, fabrication, and control of the flexible link. The combination of already well-known Lagrange and finite-element methods seems to be a great advantage in this modeling procedure. Lightwave flexible links, although known to save a large amount of operational energy, are not popular in the industry because of difficulty in their modeling and control. Following the methodology suggested, modeling is reduced to a mechanical procedure capable of efficient computer implementation. A simple controller is suggested. The controller is designed using the MATLAB simulation package, and the results are compared graphically. The lessons learned form the project are reported     

The case for free space

This article discusses the prospect of free-space optical links (FSOLs) in relation to backhaul applications as well as its technology trend, including the recent development of radio on free-space optical links (RoFSOLs). Here, we consider how FSOLs act as useful transport media, focusing on practical experience in mobile backhaul networks. We refer to studies on FSOL conducted by the Internat ional Telecommunications Union (ITU) from the viewpoint of the possible exploitation of the frequency bands above 3,000 GHz, which are outside the scope of the current Radio Regulations. As optical technologies are becoming more advanced, FSOL applications have been considered as a potential medium to provide short-range links using simple and compact equipment. Free-space transmission has advantages such as rapid deployment and relocation; however, it has to be operated under limited link lengths due to the propagation impairments.     

An optical transmitter/receiver system for wireless voicecommunication

The design of an optical transmitter/receiver system, suitable as an educational project for the demonstration of low-noise wireless voice communication in the laboratory, is described. The system, having a range in excess of 8 m, uses a VCO (voltage-controlled oscillator), operating at the center frequency of 100 kHz, to achieve voice data encoding. Optical decoding at the receiver is performed using a conventional phase-locked loop (PLL) circuit. As an optoelectronics design project, the system successfully integrates the concepts of free-space optical communication, frequency modulation, and analog electronics design, which are common to infrared (IR) remote control devices     

软切换FSO/RF链路混合编码调制算法性能分析

将自由空间光(FSO)通信链路的高速率优势与射频(RF)链路的可靠性优势互补结合,针对FSO/RF混合通信链路组网的物理层数据可靠传输问题,研究软切换机制下采用LDPC混合编码与2-PPM和16QAM调制的系统方案性能。混合系统FSO链路在Gamma-Gamma信道不同湍流强度与RF链路在Rician信道不同信噪比条件下的仿真结果表明,所述方案在软切换下达到1×10~(-6)误比特率时,不同条件下可获得1.3~8.0 dB不等的性能增益改善,显著提高在不同链路条件下FSO/RF混合通信系统的数据传输可靠性。     

多端交直流混合网扩展规划的综合法

提出了一种将混合整数规划法和证据理论相结合进行多端直流混合网扩展规划的综合法,避免了常规规划方法形成临时联接方案时的盲目性,而且可处理规划中的各种不确定性因素。给出了综合法的流程及利用证据理论进行水平年临时联接和最终扩展规划方案评估的推理网络和具体方法。以三峡联网规划为例,表明此综合方法可取得现有规划方法无法实现的功效。     

Integrated transceivers for optical wireless communications

Line-of-sight free-space optical links can provide extremely high bandwidth communications, but this usually requires that transmitter and receiver are precisely aligned. In order to allow terminals to be mobile, links must be able to track users within their field of view so that the link is maintained. There are various means to do this, but all require complex subsystems with a number of different optical, optoelectronic, and electrical components. A solid-state tracking architecture is introduced and a seven-channel tracking system demonstration described. The system is designed to operate at 155 Mb/s and is, to the best of our knowledge, the first that uses an integrated approach. Arrays of novel resonant cavity LED (RCLED) emitters that operate at 980 nm are used as sources. These are flip-chip bonded to arrays of CMOS driver circuits and integrated with the necessary transmitter optics. The receiver uses a back-illuminated detector array flip-chip bonded to arrays of custom CMOS receivers. All these components are custom and have performance substantially better than nonoptimized commercially available components. In the paper, the design and fabrication of the optics, optoelectronics, and electronics required for this is described. Successful operation of all the subsystems is detailed, together with results from an initial link demonstration.     

柔性直流输电系统交流侧中高频谐振附加阻尼抑制措施

中国鲁西背靠背直流异步联网工程和渝鄂直流背靠背联网工程均发生过高频谐振现象,柔性直流输电系统的链路延时是导致高频谐振现象发生的关键因素.文中针对柔性直流输电系统的中高频谐振问题,基于谐波线性化方法建立了柔性直流输电系统从交流侧端口看过去的等效详细阻抗模型,并分析了模块化多电平换流器(MMC)阻抗在中高频段呈现负阻尼特性的原因.然后,对比分析了在电压前馈环节采用低通滤波器、带阻滤波器和非线性滤波器等控制方式对MMC阻抗特性的改善作用与谐波抑制效果,并提出3种附加阻尼控制器,分析了其对MMC阻抗特性的改善作用.最后,以鲁西背靠背直流异步联网工程广西侧模型为例,通过PSCAD电磁暂态仿真验证了详细阻抗模型的正确性和附加阻尼控制的有效性.     

Optically powered data link for power system applications

The practicability of an optically powered data link has been demonstrated. The link has moderate bandwidth (1 kHz), accuracy (1%) and dynamic range (>60 dB) over a useful range of ambient temperatures. The link uses commercially available components, including a photodiode array fabricated using the dielectric isolation process in silicon. An application to the measurement of current in a high voltage line by means of a linear coupler is described, and experimental results are presented. Power transmission efficiency is presently low, at about 0.3% overall (electrical-to-electrical) and 5% optical-to-electrical     

馈线自动化的几种实现模式

在实现配电自动化工程中 ,馈线自动化是其中非常重要的一环。文中介绍了馈线自动化工程中常见的几种实现模式 ,即分段开断、分段隔离 ,免通信的环网自动重构系统 ;负荷开关升级型配电自动化系统 ;全线开断、然后分段隔离 ,再用电压 -时间型配电自动化系统来恢复供电 ;无功补偿自动控制系统及电压自动调节系统。并对这几种模式方案的优缺点分别作了论述。     

Diffraction-grating-based (de)multiplexer using image plane transformations

We present the concept of using image plane transformations with free-space diffraction-grating-based multiplexers. We demonstrate two examples of a diffraction-grating-based multiplexer that take advantage of image plane spatial transformations. We show that the use of such spatial transformations has unique advantages for multiplexing schemes. We also demonstrate unique system applications enabled by these multiplexers.     

基于补偿特性的并联型有源电力滤波器直流侧电压取值分析

并联型有源电力滤波器直流侧电压值直接影响谐波补偿特性,文中分析了直流侧电压的取值对补偿特性的影响。首先,分别在单相和三相系统中,针对典型的晶闸管整流加阻感负载为系统负载的负载电流,通过对等效电路的分析,得出完全补偿谐波时所需的直流侧电压理论最小值;然后,当直流侧电压小于理论最小值时,考虑在正弦脉宽调制方法下,通过仿真曲线,给出了补偿后电源电流总谐波畸变率(THD)与直流侧电压之间的定量关系,这些曲线为直流侧电压的选择提供了参考。仿真和实验验证了所述直流侧电压值选取方法的正确性。     

变电站保护系统的通用仿真方案

介绍一种变电站保护系统的通用仿真方案。利用动态连接库（ＤＬＬ）技术,按各保护的保护原理建立保护模型库,以故障计算为基础,以整定值和延时时间为判据,采取提高实时性的有效措施,按时间段扫描全部保护。采用这种方法可使保护仿真的效果既快速又准确,并具有很强的通用性,不仅适用于培训变电站运行人员,还可用于培训保护定检人员。     

Tricolor light-emitting diode dot matrix display system with audiooutput

In this paper, a novel tricolor dot matrix display system in which all the light-emitting diodes (LEDs) are modulated and encoded with audio information is presented. The novelty is on the concurrent use of the tricolor LED display for simultaneous visual message display and audio signal transmission in a free-space optical link. This is a new generation of tricolor dot matrix displays where, in addition to the usual function of LED display, they concurrently provide audio broadcasting through the visible light rays transmitted by the display panel or assembly. The system is comprised of a tricolor dot matrix display panel with an interface circuit to a computer, an audio signal transmitter, and a receiver. It also comprises an executive program that runs on the computer for the display control of characters, decorative pattern or messages on the display panel. The receiver is designed to demodulate the optically transmitted audio information, and reproduce the messages with the speaker For modulating emission of the LEDs, an oscillator is used to vary the frequency of on/off periods of the LEDs. The frequency of flicker is high enough to be indistinguishable by human eye and, hence, display appears to be constantly illuminated     

基于新型检测方法的单相并联有源滤波器

提出一种基于新型检测方法的单相并联有源滤波器。该有源滤波器采用新型基波相位和频率检测方法,基于该检测方法采用单周期复位积分方法计算出谐波电流。输入信号经过A/D变换得到数字信号,经过频率校正环节后可得到与输入信号基波分量相同角频率的信号,该信号再经过初相校正环节后就可以得到与输入信号基波分量同频率、同初相的相位信号,从而实现对输入信号中基波分量的跟踪。该相位检测方法不需要通过闭环校正,显著提高了检测跟踪速度,暂态响应时间小于20ms。利用该方法检测出电网电压基波分量单位正弦信号,采用单周期复位积分法,可以得到负荷电流基波分量的幅值,从而方便地计算出电流中的谐波分量。仿真和实验结果证明了所提方法的正确性和有效性。     

Electromagnetic torsion mirrors for self-aligned fiber-opticcrossconnectors by silicon micromachining

We report a micromechanical fiber-optic switch (1 cm×1 cm×1 mm) based on an electromagnetically operated torsion mirror which is suitable for self-latching operation. The switch is fabricated by silicon micromachining technology, and self-alignment technique is employed to align optical fibers to the mirror. A small mirror of gold finished FeNiCo/polysilicon (150 μm×500 μm) is supported by two beams, and rotated around the axis in the magnetic field induced by an electromagnet. An incident light is redirected by the mirror in a free-space smaller than 1 mm³. Multimode fibers are used for optical coupling of small loss (-2.5 dB for reflection and -0.83 dB for transmission) at a wavelength 1.55 μm. Typical switching time is 10-25 ms, and switching contrast is larger than 45 dB. Magnetic torque and optical coupling are theoretically investigated     

基于树模型的电力监控系统链路信息管理

现阶段电力监控系统中的运维存在一定安全风险,运维信息缺乏有效的管理手段,无法对运维过程中产生的大量连接链路信息进行有效的管理及关联性分析。提出一种基于树模型的链路信息管理技术,该技术通过数据采集、链路建模和实时分析三层架构实现对运维过程中产生的链路信息的管理与审计,使由于运维造成的安全事件能够快速溯源,缩短事故定位时间。同时,提出一种拓扑链路算法,该算法通过收集的链路访问信息构造访问森林模型,便于信息的查找与管理。实验表明,该算法快速有效。     

基于Snake算法的圆盘仪表示数识别技术研究

仪表示数的自动识别对于自动检测和自动控制具有重要意义,文章以圆盘仪表示数的自动识别为研究内容展开研究。提出了一种基于Snake算法的自动识别方法,整个算法分为Hough变换粗定位圆形特征、Snake算法精定位圆形特征、Hough变换检测直线特征三个环节。此方法以Hough变换检测的圆形特征为初始条件,进而根据Snake模型的内力和外力,引导Snake曲线向更加精确的圆形特征逼近。针对压力表图像展开相应的实验研究,实验结果证实了基于Snake算法的自动识别方法的有效性。     

Experimental demonstration of the "apparent wavelength"

In this paper, an experimental demonstration of the "apparent wavelength" using microwaves incident on a plane conductive surface obliquely, with the electric field polarization parallel to a reflecting plane, is presented. Standing wave measurements were obtained by utilizing the interaction between the transmitting and the receiving rectangular horn antennas using the receiving horn antenna as a probe. This technique demonstrates to the students that the wavelength along the normal, the "apparent wavelength" is longer than the wavelength of the free-space incident or reflected waves and is in agreement with the theory. Finally, the proposed technique demonstrates high sensitivity and accuracy for tutorial demonstrations of standing wave pattern measurements despite the large cross-section of the receiving antenna.<>     

PLC热备系统及其应用

通过分析AB公司PLC热备系统的硬件结构和工作原理 ,解释热备系统发生切换时出现输出跳变和存在数据不完整现象的原因 ,给出利用高速串行链路进行热备编程而解决这一问题的方法 ,并介绍了应用于大型高炉鼓风机监控中的实例