双光束干涉型光纤传感器抗偏振消衰落技术

对干涉型光纤传感器中光波偏振态的随机变化导致待检测信号衰落的原理进行了理论分析,系统地总结了目前国内外关于双光束干涉型光纤传感器抗偏振消衰落措施的最新研究成果。     

偏振态调制的消偏振衰落干涉型光纤传感器

针对低双折射光纤双束干涉型传感器两行偏振态随机变化引起的信号衰落，提出了一种新型干涉型光纤传感器的消偏振衰落方案。通过在光纤干涉仪的输出端加对光波偏振态适当的高频调制．可以使干涉信号幅度波动小于４．７ｄＢ或６．３ｄＢ（与调制信号的形式有关），通过自动增益控制电路或将输出信号除以可见度的方式，能够在信噪比有所降低的情况下消除偏振衰落的影响，实现干涉型光纤传感器的消偏振衰落。     

干涉型光纤传感器阵列消PIF技术的研究

针对低双折射光纤双光束干涉型传感器两臂偏振态随机变化引起的信号衰落,提出了一种新型消偏振方式,它可以在可见度略有下降的情况下,较好地消除偏振态变化引起的信号可见度的随机变化。该方案是通过相互正交的两个偏振态来补偿由于其中一个偏振态变化导致的干涉信号衰落。通过自动增益控制电路可以使传感信号稳定,能够在信噪比有所下降的情况下消除偏振衰落的影响,实现了干涉型光纤传感器的消偏振衰落。     

干涉型光纤传感器输入偏振态反馈控制的分析研究

光纤干涉仪中的偏振态保持或控制技术是干涉型光纤传感器研究中极为重要的一个问题.特别当干涉光的两臂中的偏振态正交时,干涉仪输出的干涉信号为零,这时传感信号将完全消失.这原则上可以采用保偏光纤技术解决,但目前保偏光纤和保偏光纤耦合器成本高、技术不完善,人们对光纤水声传感器等干涉型光纤传感器中的偏振衰落问题的解决一般采用低双折射率光纤加消偏振态衰落或偏振控制的方式.经过研究分析,可以认为光纤干涉仪中的两臂偏振态的变化总体效果等同于从第一只耦合器输入光波的偏振态变化,当该输入偏振态的变化等于光纤干涉仪中两臂偏振态的反变化时,输入偏振态补偿了干涉仪中的偏振变化,因此有可能通过控制输入端光纤的偏振态达到对光纤偏振控制的目的. 对光纤干涉仪输入偏振态的反馈控制机理做了较深入的理论分析,推导出反馈系统的反馈信号与输入偏振态的关系式,建立并根据系统闭环控制物理模型,分析了光纤偏振控制器电压初始值要求及该反馈系统可能存在的稳定点,对消偏振衰落系统的设计和制作有较大的指导意义.(PD12)     

波长解调用偏振无关光纤干涉仪的研究

针对光纤激光传感器信号解调过程中,干涉仪输出干涉条纹可见度受输入光偏振态变化以及两臂单模光纤双折射效应的影响,介绍了一种简单的光纤干涉仪消除偏振衰落技术,通过在Michelson光纤干涉仪上加两个法拉第旋转镜来提高输出条纹可见度。使用琼斯矩阵法对干涉仪系统进行理论计算,证明法拉第旋转镜旋转角度在理想的45°附近时能达到很好的消偏振效果,并通过实验进行了有效地论证。     

双M-Z型光纤微振动传感器光波随机偏振分析

对应用于分布式微振动传感的双M-Z型光纤传感器进行偏振分析,阐明光波偏振态随机变化导致时间差振动定位方法失效的原因。分析表明,光波偏振态随机变化引起两干涉输出的幅值波动,同时在两干涉输出间引入取值范围是-π~π的相位差,可使双M-Z型光纤传感器处于两个不同的工作点,造成同一相位调制产生两个不相关的干涉输出,导致基于信号相关的时间差振动定位方法失效。光路实验验证了理论分析的结果。     

基于部分保偏器件的干涉型光纤传感器

在单模光纤构成的干涉型光纤传感器中,存在偏振衰落问题,将导致干涉效率降低.而为了消偏振衰落采用全保偏器件的光纤传感器成本过于高昂,影响其实用性.以马赫.泽德干涉仪为基础,用反馈信号控制偏振控制器加起偏器的结构消除了偏振衰落,构造了基于部分保偏器件的干涉型光纤传感器.实验得到系统输出信噪比稳定在60 dB左右.     

输入偏振态控制的光纤传感器复用系统的研究

提出了在干涉型光纤传感器复用系统中将各传感器的最佳输入偏振态反馈控制信息叠加用于复用系统最佳输入偏振态控制的方案,并对复用系统中各单元最佳输入偏振态的较差分布时的控制效果进行了理论分析。对达到这一较差分布的概率进行了计算。研究表明,该方案简单可行。经过信号处理能使各个光纤传感器在降低信噪比的情况下使干涉仪的输出信号的可见度为1,人而消除了复用系统中各单元的偏振衰落。     

基于马赫-曾德尔原理光纤传感器偏振态的研究

基于马赫-曾德尔原理的光纤传感器广泛应用于管道的实时监测中,分析了此类光纤传感器的输出功率随入射光偏振态及光波在长距离光纤传输中偏振态变化的影响。通过Matlab仿真研究了分布式光纤传感系统的偏振衰落,论证了光波传输中的偏振衰落现象对输出条纹的可见度产生了很大的影响。提出了一种利用动态的偏振控制系统对光波偏振态进行控制从而减少偏振衰落的方法,并且展望了改进后的分布式光纤传感器在工业管道的探测领域中具有相当广阔的前景。     

干涉型光纤传感器复用系统的消偏振衰落技术

提出了在干涉型光纤传感器的复用系统中将各个传感器的输入偏振态反馈信号加权叠加用于复用系统输入偏振态控制的方案。经分析，该方案可达到的最小可见度与文献分析的复用系统输入偏振态控制的理想效果相接近。经过信号处理能使各个光纤传感器的可见度均达到其最大值１，从而消除了复用系统中各单元的偏振态衰落。     

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.     

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.     

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.     

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.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

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.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks