基于FBG传感系统的可调光滤波器非线性研究

采用光纤布拉格光栅(FBG)传感系统研究压电陶瓷(PZT)驱动法布里-珀罗(F-P)型可调谐光滤波器(TOF)的非线性特性。基于多光束干涉理论建立了TOF的非线性模型,推导了透射带波长和自由光谱范围(FSR)对驱动电压的非线性响应;基于FBG传感系统测试了F-P型TOF的波长非线性,并采用多项式拟合对其进行描述,实测F-P型TOF波长的非线性误差最大为1.006 nm;基于F-P型TOF的非线性模型,研究了其波长定位误差,并提出采用参考光栅的方法降低波长定位误差。实验表明,F-P型TOF的波长随机误差可由73～81 pm降至12 pm以下。     

FBG解调实时校正技术研究

在基于可调谐F-P的FBG解调系统中,由于驱动电压与扫描波峰的关系不固定,增加了系统误差。为此研究了实时校正技术。首先,通过方案比较和分析,设计了并联型的实时校正系统,此系统可以通过多个参考点实时校正PZT的非线性问题以及可调谐F-P滤波器的结构性误差。然后,通过实验分析了PZT驱动电压与可调谐F-P波峰的关系,设计了快速分段算法。最后,针对此系统,设计了以现场可编程门阵列(FPGA)为核心的信号处理单元,将解调系统的控制、滤波计算和数据压缩等电路集成在FPGA芯片内部,保证了系统的实时性。实验结果表明,该系统的均方误差为2.2pm,最大误差为6pm。解决了此类解调系统受可调谐F-P滤波器精度限制的问题,提高了测量精度。     

基于重叠多光栅的动态应变传感特性研究

利用重叠多光纤布拉格光栅(FBG)反射谱的时间同 步性,实现了动态或静态应变信号的高速传感与解调。给出了基于光纤F-P 可调谐滤波器(FFP-TF)的重叠多FBG解调系统及其时域重构的实现方法,重叠多FBG在FFP- TF 三角波扫描电压与动态应 变信号测量时产生时域上等间隔分布的传感脉冲,解调系统采用质心法硬件解算并结合平滑 滤波的方法可满足速度与解调精 度的同时测量需要。在重叠双FBG与500Hz FFP-TF扫描速率条件下 可产生2kHz的传感脉冲,动态应变信号的测量 带宽相对于单FBG解调系统提高了4倍,静态条件下的波长偏移小于±4pm。给出了影响重叠多FBG动态应变信号解调结果失真度的影响因素。     

动静态监测光纤光栅传感信号的实验研究

基于可调谐光纤TF Fabry-Pent（FP）滤波扫描传感光纤Bragg光栅（FBG）反射峰的原理．提出一种新颖的探测方法,分别从动静态两方面监测传感FBG反射谱与TF F-P透射谱的合成谱。实验中．通过加载到TF F-P滤波器的驱动信号的不同,在静态监测下,模拟并分析了光信号功率与转化电压的趋势图以及多次实验中探测到最大信号时两者的关系;用双踪示波器动态实时监测并分析了经光电探测（PD）及其放大调理电路转换后的电压变化信号。实验结果表明．PD探测的最大值与传感FBG反射峰对应。经过标定后的系统分辨率可达1pm,测量精度为0．01nm。     

基于最小二乘法的电力电缆FBG传感测温系统

为了提高电力电缆测温系统的测量精度和速度,提出了以光纤梳状滤波器代替参考光栅提供拟合数据参考点,采用最小二乘法拟合光纤Bragg光栅波长和F-P可调谐滤波器调谐电压的线性关系,通过F-P可调谐滤波器解调FBG传感器中心波长变化的方法,完成对电力电缆温度的测量.研究表明,光纤梳状滤波器能够代替多个恒温参考光栅实现波长标定,对反射波长的测量误差＜5pm,温度均方误差≤0.7 ℃.     

低电压驱动的MEMS F-P可调光学滤波器研究

基于微机电系统（MEMS）技术,研制了一种新颖的光学腔与静电驱动器分离的Fabry-Pérot（F-P）可调谐滤波器。从光学设计、MEMS结构设计、制造工艺与器件测试等开展了F-P可调谐滤波器的研究,成功制备了工作在以1550 nm波长为中心、调谐范围为40 nm和驱动电压低于30 V的MEMS F-P可调滤波器。测试...     

F-P标准具和参考光栅相结合的高稳定性FBG解调系统

为了提高光纤布喇格光栅（FBG）解调系统的稳定性和准确性,避免由于压电陶瓷的迟滞性、蠕变性以及温度变化引起的法布里-珀罗（F-P）滤波器驱动电压与透射波长不成线性的问题,采用了可调谐环形腔激光器作为扫描光源,与F-P标准具、温补参考光栅、传感光栅3个单独的通道结构相结合的FBG解调方法。通过理论分析和实验验证,选择中值滤波加滑动平均滤波的方法滤除噪声,采用基于强度阈值的频谱相关寻峰算法更加准确地找到反射谱峰值的位置。结果表明,每个通道单独分开的解调方案的波长长期稳定性可达0.4pm,温度与波长的线性度高于99.90%。该系统能够实现对温度、应变等参量的稳定性的测量。     

用可调谐F-P滤波器实现分布式应变与温度同时测量系统

理论分析了FBG光纤光栅和长周期光纤光栅应变与温度同时测量的传感原理.在分析实现光纤光栅传感技术解调的基础上,重点研究了可调谐光纤F.P滤波器解调法.提出采用可调F-P滤波器实现分布式应变与温度同时测量系统的解调方案,较好地实现了多点应变与温度的同时测量.这种方法的测量精度较高,其中测量应变的灵敏度可以达到9με,测量应变的灵敏度为15℃.     

一种光纤Bragg光栅传感器解调系统的实验研究

实验研究了基于可调谐光纤激光扫描的光纤Bragg光栅（FBG）传感器解调技术。系统由可调谐光纤F—P（TFFP）滤波器、掺Er光纤放大器（EDFA）、隔离器和耦合器组成可调谐激光光源,根据光电探测器输出波形、驱动电压与应变问关系实现了应变解调。分析了影响系统解调精度的原因,并做了相应的改进。实验测得,应变与TFFP驱动电压间的线性度达到0．998,且能达到1．26μstrain的高应变分辨率。     

基于可调谐FP滤波器的光纤光栅解调系统

为了进一步提高光纤光栅解调系统的性能,提出和研究了一种新颖的基于可调谐F-P(Fabry-Perot)滤波器的光纤光栅解调技术,并以此为基础构建了探测系统。系统使用一个固定波长的参考光纤光栅作为波长参考元件,通过对传感光纤光栅与参考光纤光栅的波长测量与差值运算,消除了可调谐FP滤波器腔长漂移对测量精度的影响。给出压电陶瓷电压对应的伸长量,有效地减小了压电陶瓷非线性对测量的影响,提高了光纤光栅波长的测量精度。在测量范围内,最大非线性偏差为0.5%。     

一种结合比特翻转的自适应置信传播算法

提出了一种结合比特翻转的自适应置信传播迭代译码新算法,称之为"BP 比特翻转"算法.首先详细描述了新算法的整个流程,然后在相同仿真条件下比较了传统"BP"和"BP 比特翻转"两者的性能和平均迭代次数,发现新算法要优于传统的"BP"算法,特别是在最大迭代次数较小时,优势就会显得更加突出.     

一种部分并行干扰对消因子的计算方法

在CDMA系统中,多用户检测是一种行之有效的方法。而具有部分干扰因子的并行干扰抵消检测器则是目前多用户检测技术中最简单、有效的接收机,但长期以来,部分干扰因子的确定大多根据实验,缺乏理论支持。该文在基于MMSE准则下,给出了一个两级PPIC接收机的部分干扰因子的计算公式。计算机仿真表明它具有良好的干扰消除能力,且对干扰信号功率和噪声估计偏差不敏感。     

一种高精度的TOA估计方法

提出了一种 CDMA系统的高精度的信号到达时延(TOA)的估计方法。在不提高采样频率的情况下,使用积分-清除电路对接收信号进行采样,将离散信号用离散傅里叶变换(DFT)转换到频率域中,然后根据 CDMA信号模型和多径信道模型以及已知的扩频码的离散频谱,估计出信号相对于一个码片周期的整数部分 TOA;再在离散频率域中用最小二乘法估计出信号到达的小数部分 TOA,该方法即使在采样频率不高的情况下,也有很高的精度,而且运算量小,因此是一种有效的高精度 TOA估计方法。     

Joint estimation of TOA and DOA in IR-UWB system using a successive propagator method

Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm.     

An all-optical method of developing data communication system with error detection circuit

The basic criterion of data communication is that received data should exactly be the replica of the transmitting data. If any error is introduced in the received data, then data transmission should be stopped immediately. In this article the authors have developed an all-optical method of data communication system with error detection mechanism that works with frequency encoded data. Basic building blocks of the proposed data communication scheme are parity generator and parity checker which are developed from all optical XOR logic gates. Simulation results testify the feasibility of the proposed scheme. These logic gates are developed exploiting nonlinear polarization rotation based frequency conversion and switching character of semiconductor optical amplifiers. The scheme with frequency encoded data, high speed of frequency conversion and polarization switching action of semiconductor optical amplifier offers secure, error free, faster data communication network.     

一种利用发光光谱估计LED正向电压的方法

提出了一种通过发光光谱估计发光二极管(LED)正向电压的方法。推导了LED正向电压与结温的关系,探讨了利用发光光谱估计结温的方法,从而建立了发光光谱和正向电压的联系。本文方法不需要直接测量结温和理想因子等参数,只由发光光谱就可得到较为准确的LED正向电压值。实验结果表明,正向电压的光谱估计值和实际测量值能够较好的吻合。     

Hybrid prediction-based pixel-value-ordering method for reversible data hiding

Pixel-value-ordering (PVO) is an effective and promising method of reversible data hiding (RDH) and has received much attention in recent years. To improve performance, a pixel-based PVO (PPVO) method was recently introduced to predict the pixels to be embedded in a pixel-wise manner instead of the block-wise manner used by PVO. However, for PPVO, the surrounding neighbors of the predicted pixels are underutilized; moreover, its embedding does not adapt to the local complexity of the image to be embedded. To overcome the shortcomings of PPVO, this paper proposes a novel PVO method based on hybrid prediction for RDH. First, the surrounding neighbors of the pixel to be predicted are fully utilized by a hybrid prediction method, which combines rhombus prediction and pixel-wise prediction. Second, a modified embedding scheme based on multiple histograms is presented for adaptive embedding. Experimental results show the superior performance of the proposed method by comparing it with state-of-the-art RDH methods.     

An effective network congestion control method for multilayer network

The congestion control problem in a single node network has been solved by the nonlinear feedback control method,which has been proven to be effective and robust for different router’s queue size.However,these control models are based on the single layer network architecture,and the senders and receivers are directly connected by one pair of routers.With the network architecture being more and more complex,it is a serious problem how to cooperate many routers working in the multilayer network simultaneously.In this paper,an effective Active Queue Management（AQM）scheme to guarantee the stability by the nonlinear control of imposing some restrictions on AQM parameter in multilayer network is proposed.The nonlinear control can rely on some heuristics and network traffic controllers that appear to be highly correlated with the multilayer network status.The proposed method is based on the improved classical Random Early Detection（RED）differential equation and a theorem for network congestion control.The theorem proposed in the paper proved that the stability of the fluid model can effectively ensure the convergence of the average rate to its equilibrium point through many routers in multilayer network.Moreover,when the network capacity is larger,the proposed scheme can still approach to the fullest extensibility of utilization and ensure the stability of the fluid model.The paper reveals the reasons of congestion control in multilayer network,provides a theorem for avoiding network congestion,and gives simulations to verify the results.     

CCD调制传递函数测量方法的改进

本文对目前所采用的测量ＣＣＤ调制传递函数方法进行了分析,并此基础上提出了改进的测量方法,改进后的方法不仅继承了原来方法的优点,同时其测量和测量结果的可靠性都有较大的提高。