基于非均匀采样的光纤光栅解调系统

鉴于重叠多光纤Bragg光栅(FBG)传感器均匀采样时遇到的数据频谱混叠问题, 提出利用扫描周期随 机变化的正弦波实现传感FBG的非均匀采样方法,并在一种基于可调谐F-P滤波器的 FBG解调系统中得到成功应用。实验结果显示,本文方法能够很好避免混叠现 象,并且还能以低于Nyquist采样频率对信号进行采样分析。     

基于DFB激光器解调技术的光学电流互感器

针对交流电流的测量,提出了一种基于分布式反馈（DFH）激光器解调技术的光学电流互感器（0CT）。OCT的传感部分运用光纤Bragg光栅（FBG）和超磁致伸缩材料（GIⅢ①作为传感器探头,同时应用DFB激光器对FBG进行解凋,实现交流电流的测量。对于这种新型的OCT进行了理论分析和实验研究,实验测得系统传感灵敏度可达到1...     

基于FPGA的时延辅助定位FBG传感系统的研究与设计

由于受光源谱宽和光纤Bragg光栅传感波长移动范 围的限制,FBG传感系统中可复用的FBG数量 受到很大限制。为了解决这种限制问题,提出通过传感信号的时间延迟对传感FBG进行定位 的方法。 设计出基于FPGA的时延辅助定位FBG传感系统,用Fabry-Peror(F-P)腔和时延定位结合的 方式对传感信息进 行解调,用FPGA进行数据处理。搭建了实验系统,进行了简单的实验。实验结果表明, 本文系统增加可复用FBG数量的方法实用性强,精度高。     

FBG传感器在巷道掘进中的应用研究

采用光纤Bragg光栅（FBG）传感器监测了巷道模型的掘进过程。利用FLA^3D软件对巷道模型进行了掘进过程的应力分析,根据应力分布情况在巷道模型中布设了15个三维应变FBG传感器和3个温度FBG传感器,通过四通道SM125解调仪对传感信号进行系统解调以及数据存储。该传感系统测量精度高,检测的应力变化与FLAC^3D软件模拟结果吻合性好,表明FBG传感器在土木工程的监测中有较好的应用前景。     

一种新型具有温度补偿功能的光纤光栅交流电流互感器

为了消除温度对实现电流测量的影响,提出了一种具有温度补偿 功能的光纤Bragg光栅(FBG)交流电流互感器。利用两个FBG和超磁致伸缩材料(GMM)组成的 传感单元分别放置在两个相邻对称的铁磁回中,并加上两个方向相反的直流偏置磁场,利用 匹配检测方法对两只FBG进行解调,实现交流的测量。测量结果表明,在温度的影响下,系 统的静态工作点几乎未发生变化,在线性区测得最大电流为93.78A , 可获得1.68%的满量程精度。这种FBG电流传感器不仅可以测量交流电 流,也可以实现直流电流的测量。     

基于光纤激光器的光纤Bragg光栅传感技术

分析了掺Er光纤激光器(EDFL)的基本原理和光纤Bragg光栅(FBG)传感机理,组建了一种基于环形腔EDFL的FBG传感系统,其中FBG既作为滤波器起波长选择、又充当传感器起感测外界温度压力变化的作用.实验研究了经过温度增敏工艺处理过的FBG温度特性,传感系统温度分辨率优于0.3℃.换用荧光光源和经悬臂梁粘贴增敏处理的FBG,对比了在相同作用力下采用该系统前、后输出传感信号的光谱形状,结果表明,该技术方法可以有效消除FBG的啁啾对传感信号的影响,方法简单、信噪比高,适用于中远距离的FBG传感测量系统.     

FBG传感器微弱信号预处理

针对光纤Bragg光栅(FBG)传感器微弱信号,设计了一种具有电流电压转换,多级放大和滤波功能的低噪声光电信号预处理电路。仿真实验表明,该电路具有增益大、信噪比大、灵敏度高等特点,满足FBG传感系统的要求,可实现nW级微弱光信号检测。     

功率加权法用于光纤Bragg光栅特征波长检测

提出了一种用于光纤Bragg光栅(FBG)传感系统中反射波位移检测的算法.采用FBG反射波波长对光功率的加权平均作为特征值进行数据处理,用于FBG传感温度补偿系统中应变参量与温度参量的分离.研究结果表明:在光源扫描步长为50 pm时,使用该算法的FBG传感温度补偿系统的检测灵敏度达到传统中心波长法检测灵敏度的10倍左右.     

一种测量范围可调的FBG流速传感装置

基于锥形分速装置,研制了一种光纤Bragg光栅（FBG）流速传感器。利用FBG压强传感机构进行传感信号解调,同时利用开关控制流速管不同开孔的开闭状况。传感器的动态感测范围可达92．5-802．3mm／s,流速检测灵敏度为0．4mm／s,并且对温度不敏感。优化FBG压强传感机构及流速管的相关参量,能够进一步提高传感装置的...     

具有温度补偿功能的双匹配FBG振动传感系统研究

为了提高光纤Bragg光栅(FBG)振动传感系统的 解调灵敏度和解调范围,消除环境温度对解调信号的影响,设计了一种具有 温度补偿功能的双匹配FBG振动传感系统。系统采用两个中心波长对称地位于传 感FBG两侧的透射式匹配FBG,建立 了两个互补对称的传感通道,并利用差分原理实现振动传感。通过Matlab软件对系统性能进 行了仿真分析,结果表明,与传 统方法相比,本文方法有效地提高了系统解调灵敏度和解调范围。将匹配FBG与热电制冷器( TEC)集成封装,并建立温度补偿判断通道,当 判断通道输出电压超过已设置好的阈值时,利用TEC改变封装环境温度,使匹配FBG 与传感FBG中心波长重新匹配, 实现系统温度补偿。经实验测试,系统的归一化解调灵敏度为5.168/ nm,解调范围为1.2nm,判断通道的归一化阈值电压 为0.890。在4种不同环境温度下,利用本系统 对同一振动信号进行测量,实验结果验证了系统温度补偿的可行性。     

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.     

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.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.