长周期光纤光栅的一种温度补偿方法

研究了长周期光纤光栅的温度和应变特性,发现其透射中心波长随温度升高向长波方向漂移,随应变增大向短波方向漂移。根据这一特点,采用有机玻璃材料封装这一简单而有效的方法来补偿长周期光纤光栅中心波长随温度的漂移,补偿后的温度漂移系数减小到仅为3.7 pm/℃,有效地抑制了温度变化对中心波长漂移的影响,大大提高了用长周期光纤光栅测量液体折射率等物理量的精确度。     

一种新型光纤光栅温度补偿装置

光纤布拉格光栅(FBG)中心反射波长随温度变化会发生漂移,影响光纤激光器输出波长的稳定性和光纤光栅传感器精度.为消除光纤光栅中心波长温漂特性,设计了一种新型光纤光栅温度补偿装置,详细阐述了其工作原理,并理论推导了点胶位置的计算公式.这种新结构易调整光纤光栅粘结位置,从而可调整光纤光栅温度补偿有效长度.为验证结构设计和理论分析的正确性,搭建了实验系统,并对封装前后光纤光栅中心反射波长温度漂移率进行了测试.测试结果表明,在-30～70℃温度范围内,封装前光纤光栅中心反射波长的温度漂移率为0.0095 nm/℃,封装后中心反射波长温度漂移率仅为0.0002 nm/℃,温度稳定性提高了约40倍.     

增敏型级联双参量测量的光纤传感器北大核心CSCD

旨在有效解决液体折射率检测中温度和折射率交叉敏感的问题,研制了一种增敏型光纤光栅(FBG)级联马赫-曾德尔(M-Z)结构的温度、折射率双参量测量的光纤传感器。通过多次熔接实验,调节相应参数将单模光纤(SMF)和薄芯光纤(TCF)进行拉锥熔接;然后在TCF的另一端熔接无心光纤(NCF),制备出M-Z光纤干涉仪;再在NCF末端级联上铝制毛细管增敏封装后的光纤光栅(FBG),最终完成双参量测量的光纤传感器的制备。根据M-Z干涉原理及FBG模式理论,计算了增敏FBG理论的温度灵敏度,给出了传感器的灵敏度系数矩阵与温度、折射率与透射谱的波长漂移量的理论公式。搭建了温度、折射率传感测试系统,实验结果表明:在15~85℃温度范围内,随着温度增加,该传感器的透射谱逐渐红移,封装后的FBG和M-Z结构的温度与波长偏移量线性相关系数分别为0.96323和0.91577,温度灵敏度分别为33.71 pm/℃和11.58 pm/℃;在室温下(25℃),液体折射率在1.333RIU~1.34235RIU范围内,随着折射率增加,FBG透射谱不发生偏移,M-Z透射谱逐渐蓝移,折射率与波长偏移量线性相关系数分别为0和0.98761,折射率灵敏度分别为0 nm/RIU和-493.51322 nm/RIU。该传感器可以有效提高温度、折射率的检测精度和灵敏度,可应用于环境、生物、石油化工和食品生产等领域。     

应用于液体检测的级联长周期光纤光栅的温度减敏封装结构

研制了一种基于级联长周期光纤光栅对(LPFGP) 用作液体折射率检测的聚合物封装温 度减敏的新型结构。选用负热光系数的OE4110聚合物材料作为封装的 基底材料,封装结构中引入一个特殊的凹槽,方便 待测溶液通过通孔进入。封装后的LPFGP谐振波长温度灵敏度约10pm /℃,而相同参数的未封装的LPFGP的温度灵敏 度为120pm/℃,封装后的LPFGP大大降低了传感器谐振波长对温度变 化的灵敏度。本文的 封装装置融保护和温度补偿功能于一体,特殊的结构设计使之适用于液体折射率的检测。     

低温环境下FBG温度传感特性研究

在低温环境中,光纤光栅(Fiber Bragg Grating,FBG)材料的热膨胀系数和热光系数会发生改变,从而影响其温度传感特性。文章通过实验研究了裸光纤光栅传感器和黄铜管封装的光纤光栅传感器在低温下的温度传感特性。结果表明,在80~300 K温度范围,裸FBG温度传感器的灵敏度为6.43 pm/K,线性度为0.974,在80~230 K温度范围,温度与光纤光栅的中心波长呈现非线性关系;黄铜管封装的FBG温度传感器,在整个温度范围内灵敏度可达26 pm/K,线性度为0.996,较裸FBG温度传感器均有较大提升。对比实验表明,对光纤光栅进行封装,可以提高其温度灵敏度和线性度,改善温度传感特性。     

封装对长周期光纤光栅的影响

对于长周期光栅,谐振波长阶数越高,封装材料折射率对其特性的影响越大;封装材料折射率小于包层时,随封装材料折射率增大,波长减小;封装材料折射率大于包层时,波长向长波长移动1.5nm.研制了一种负热胀系数的材料用于封装光栅,使光栅波长的温度系数不大于5.1×10-3nm/K.     

磁流体包覆薄包层光纤光栅磁场传感研究

利用磁流体替代光纤布喇格光栅(FBG)的部分二氧化硅包层,制作了一种磁流体封装薄包层FBG结构的磁场传感器,研究了传感器对磁场和温度的响应特性。结果表明,在5.0～20.0mT的磁场范围内,传感器的波长灵敏度和功率灵敏度分别为34.9pm/mT和-1.063dBm/mT,波长线性响应度达到了99.2%。封装工艺未改变FBG波长随温度线性变化的特性,但受磁流体磁光效应影响,其温度灵敏度减小到9.2pm/℃。该传感器可实现磁场测量中的温度补偿,方法简单、易于实现。     

基于双金属结构的光纤光栅温度不敏感滤波器

为提高光纤陀螺宽谱光源的平均波长稳定性,提出了一种用60μm超短光纤光栅制作带宽11.77 nm温度不敏感滤波器的方法。利用金属材料的热膨胀系数差,设计了双金属温度补偿结构,能够随温度的升高/降低对光纤光栅压缩/拉伸,有效地补偿光纤光栅由热光效应引起的波长变化。在30～60℃的温度范围内,光纤光栅的温度灵敏度系数为0.15 pm/℃,较未补偿前降低了60倍以上。该结构具有较好的温度不敏感性,可作为光源滤波器提高光源的平均波长稳定性并有望用于高精度光纤陀螺。     

基于纤芯失配多模干涉的光纤折射率传感器

基于多模干涉效应的单模-多模-单模(SMS)结构光纤折射率传感器通常需要进行包层腐蚀来提高灵敏度,而且易受环境温度影响。为克服SMS结构的这些不足,提出了一种新型的基于纤芯失配多模干涉的光纤折射率传感器,由单模光纤-色散补偿光纤-单模光纤(SMF-DCF-SMF)级联光纤布拉格光栅(FBG)构成,长度不超过100mm。对其灵敏度、线性范围和温度特性等进行了测试,实验结果显示在测量折射率为1.33～1.39的折射率液时,特征波长与折射率呈线性关系,灵敏度为232.8nm,级联的FBG具有良好的温度校准功能。     

高灵敏度长周期光纤光栅温度传感器的研究

采用纤芯弹光系数大于包层弹光系数的长周期光纤光栅,且在其包层外面涂覆一层随温度升高折射率减小的薄膜材料,同时采用线膨胀系数较大的金属封装光栅等三种增敏措施,可提高长周期光纤光栅温度传感器的灵敏度,测得其灵敏度系数为0.237 5 nm/℃,温度分辨率小于0.1 ℃.     

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