基于色散补偿光纤的高速光纤光栅解调方法

本文提出并论证了一种光纤光栅高速解调的新方法, 利用色散补偿光纤的色散效应, 将光纤光栅的波长漂移信息转换成时域信息. 采用脉冲激光器作为光源, 仅需一个光脉冲可获取单根光纤上所有光纤光栅的反射光脉冲, 再根据各个光栅反射回光脉冲的延时变化即可实现波长的解调. 本方法可用于准分布光纤光栅传感网络解调, 系统采用全光纤结构, 无需波长扫描, 大大提高了解调速度. 本文搭建了测试系统进行实验验证, 对3个光纤光栅组成的准分布式传感网络进行了解调, 实验结果表明, 解调出的光纤光栅布喇格波长线性度好, 解调速度最高可达1 MHz, 采样数据取10次平均后解调线性度可达0.9969, 解调误差约为27.8 pm.     

Beam and phase effects in angle-beam-through-transmission method of ultrasonic velocity measurement

The accuracy of a plane wave approximation for phase velocity measurements in isotropic and anisotropic material using the angle-beam-through-transmission method has been investigated numerically and experimentally. In this method the velocity is measured in different propagation directions as a function of incidence angle. The effect of two factors on the measurement accuracy have been discussed: intrinsic phase shift of the transmitted signal through a fluid-solid interface and beam diffraction due to the finite beam size of receiver and transmitter. It is shown that the interface-induced phase shift can introduce an error in time delay measurements of the shear wave after the first critical angle and that this time delay error can be accurately corrected for. Numerical results obtained by a time-domain beam model show that except at the critical angles, the finite width of the transmitter and receiver only affects the amplitudes of the transmitted signals and has almost no effect on the measured zero-cross time delay; therefore the plane wave approximation for obtaining phase velocity from the measured time delay data by this method and the plane wave interface-induced phase correction are fully applicable.     

A free-space-based differential phase shift quantum key distribution scheme with higher key creation efficiency

Differential phase shift quantum key distribution scheme has been improved by introducing a passive path selection structure at the transmitter including two polarization controllers used to mark the photon pulses and a polarizing beam splitter to distinguish these pulses so that can make different time delay at the receiver. Theoretical analysis indicates that a free-space-based differential phase shift quantum key distribution system with this proposed improvement will have high efficiency with the utilization ratio of photons reaching 100% under ideal condition.     

自适应光学系统的数值模拟：直接斜率控制法

采用直接斜率控制法完整地实现了对自适应光学（ＡＯ）系统的数值模拟，系统研究了带自适应光学校正的激光大气传输规律。提出了对计算出的位相进行了“剪接”的办法，解决了残余位相方差与自适应光学的校正效果没有对应关系的问题。证明可以把快速傅里叶变换法（ＦＦＴ）用于透镜成像的聚焦计算，与积分法得到相同的结果，报道了对于一定的延迟时间，当大气横向风速大于一个阈值时，自适应光学补偿比安全相位补偿的效果还要好，表明     

影响空间变化偏振矢量光束强聚焦后焦斑移位的因素

利用衍射积分公式数值模拟了不同阶次的空间变化偏振矢量贝塞尔高斯(BG)光束经过强聚焦系统后在焦点附近的强度分布。数值结果显示空间变化偏振矢量BG光束聚焦后在光束传播轴负方向存在焦斑移位现象,其焦斑移位的大小与光束的模阶次、光束宽度、波长以及局部偏振状态密切相关。矢量光束偏振态的变化依靠液晶相位延迟器(LCVR)的相位延迟角度来控制,由于LCVR的相位延迟角度可以在0～π之间连续变化,从而改变光束的局部偏振状态,间接实现了对矢量光束焦斑移位大小的实时控制,在光学微操纵领域具有潜在的应用价值。     

参量阵差分Pattern时延差编码冰下水声通信方法

为提高差分Pattern时延差编码水声通信方法的通信速率以及抗多途能力,使其能有效适用于冰下水声环境,提出了基于参量阵的差分Pattern时延差编码水声通信方法,推导了Pattern码的参量发射原理,分析了参量阵发射对该方法性能的影响,利用参量阵发射产生低频宽带窄指向性声柬,减少了声线触碰上下边界的次数,提高了系统抗多途的能力。冰下水域外场试验结果表明:本方法可有效抑制多途效应,同时低频宽带特性提高了系统通信速率。      

Dual-beam-reflection phenomenon due to leaky modes in a photonic band gap

We show a dual-beam-reflection phenomenon for a Gaussian beam illuminating a hybrid structure of a dielectric waveguide and photonic crystal (WG-PC) inside the photonic band gap by numerical simulations. One reflection beam has a giant negative lateral shift, but the other has a positive lateral shift. The finite-difference time-domain (FDTD) simulations show that this phenomenon has a time delay effect and comes from the leaky surface mode of the hybrid structure. Field profile of the leaky mode demonstrates a strong localized stationary field in the higher dielectric medium. Furthermore, the maximum lateral shift is almost two times of the waist of the incident beam.     

基于延时干扰的感应电能传输系统分岔频率输送控制

本文针对感应电能传输系统分岔频率的输送控制问题, 提出一种基于延时干扰的变轨控制方法. 该方法在反馈控制环节中加入一段延时干扰, 通过调节延时参数, 可使系统相轨迹流在各稳定极限环吸引子间自由切换. 文中以原副边均为串联谐振的感应电能传输系统为例, 对该方法的机理及实现方案进行了研究, 并通过仿真和实验验证了其有效性. 论文的研究结果对类似多吸引子分岔行为的输送控制可提供一定的理论参考. 关键词： 感应电能传输 频率分岔 输送控制 延时干扰     

Doppler effect performance for multiple hops optical connections in LEO satellite constellations

Low earth orbit satellite constellations using laser inter-satellite links are recognized to be capable to satisfy the increasing broadband communication demands. However, Doppler in inter-satellite laser communications can degrade the performance of the optical space network. It is crucial to study the Doppler performance on the high precision system. The expression of Doppler wavelength shift for multiple hops laser inter-satellite links is proposed in the paper. The calculation of Doppler wavelength shift in multiple hops ISL is studied with the consideration of location, motion and onboard characters of the satellites. Theoretical and numerical analysis show different routing way between two certain distant satellites will lead to different Doppler wavelength shift and signal transmitting time, and the variation of Doppler wavelength shift is mostly depend on the number of laser inter-satellite links hops; reasonable onboard time delay can augment signal transmitting time with little influence to the Doppler wavelength shift. It is hoped that the study can help the routing selection of the optical space network and system compensation.     

Research on six degrees of freedom compound control technology for improving photoelectric pod pointing accuracy

High line-of-sight (LOS) pointing precision is a prerequisite for improving the laser confrontation capability of a photoelectric interference pod. In a traditional photoelectric pod, the time delay in TV tracking reduces the system phase margin, system stability and LOS pointing precision. In view of this deficiency, a normalized LMS algorithm is introduced to compensate for the TV camera delay in the inner gimbal position loop of a two-axis and four-gimbal structure, which can allow a pod to avoid system phase margin reduction. Meanwhile, a fast steering mirror (FSM) system is used to improve the LOS pointing precision. First, this paper proposes a normalized LMS algorithm. Second, a compound control structure, with an outer gimbal analog controller and an inner gimbal lag–lead controller, is designed. Finally, the FSM beam control precision is analyzed. The experimental results show that the normalized LMS algorithm yields almost no delay; moreover, the azimuth and pitch beam control accuracies are greater by a factor of 15 and 3, respectively, compared with those of a conventional photoelectric pod.     

电光调制2×490°相移空间光学桥接器

基于LiNbO3晶体的双折射和电光效应设计制作了一种2×4的90°相移自由空间光学桥接器。该桥接器利用晶体的双折射效应进行信号光和本振光的分光/耦合,电光效应引入相位调制,在给定电场条件下实现2×4 90°空间光学桥接器的功能。对空间光学桥接器进行了实验测量和分析。实验结果表明该桥接器性能良好,相位连续可调,相位误差可通过电压调制补偿,应用于相干接收系统。     

基于时延补偿机理的网络化输出反馈控制器设计

本文考虑前向和反馈通道均存在网络时延的网络化控制系统,提出了一种新的动态输出反馈控制器的设计方法.针对状态可测和不可测两种情况,整个设计过程采用不同的时延补偿机理,来主动地消除网络时延的影响.同时,讨论了闭环网络化控制系统的稳定性.最后的仿真实例表明了该方法的有效性.     

Delay Effect on Coherent Transfer of Optical Frequency Based on a Triple-Pass Scheme

We demonstrate a triple-pass scheme for coherent transfer of optical frequency and the delay effect on the fiber phase noise compensation. It is theoretically proved that the delay effect consists of both fiber delay and servo delay. The delay effect confines the servo bandwidth within 1/8 and induces a residual fiber phase noise after noise compensation. For a 25-km-long fiber, the servo bandwidth is found to be around 1 k Hz, and the fiber phase noise is suppressed approaching to the theoretical limitation. The triple-pass scheme enables the simultaneous transfer of optical frequency to multiple remote users. The performance of noise compensator in the triple-pass scheme can achieve a similar level result compared with that in the double-pass scheme.     

变时延遥操作交会的Smith模糊控制

针对地面遥操作空间航天器进行交会的情况,研究了变时延条件下遥操作交会逼近段的轨道控制问题.利用根轨迹法分析了时延对遥操作交会控制的影响;通过设计时延缓冲器,将变时延系统转化成了定常时延系统;基于相对轨道动力学方程建立了被控对象的预测模型,利用Smith预测原理设计了定常时延下的多变量Smith预测器,使得控制器与执行器的输入不受时延的影响;同时采用模糊控制方法,以消除模型不确定性等因素的影响;最后,利用半实物仿真系统开展仿真试验,对本文所述方法进行了验证.仿真结果表明,通过采用带时延缓冲器的Smith模糊控制的方法,能有效降低地面遥操作交会过程中变时延以及模型不确定性的影响,提高交会成功率和精度.     

Boundary control of an axially moving string via fuzzy sliding-mode control and fuzzy neural network methods

The objective of this study is to develop intelligent control schemes for the transverse vibration reduction of an axially moving string. The proposed approaches are backboned by the methods of fuzzy sliding-mode control (FSMC) and fuzzy neural network control (FNNC). In practice, the control effort for the system is realized through a typical mass-damper-spring (MDS) system attached at the right-hand side boundary of the moving string. The dynamic coupling between the string and the MDS system provides an actuation force to suppress transverse vibration. In the first phase of this study, the framework of FSMC is designed, in which the techniques of region-wise linear fuzzy logic control design and generic algorithm technique are employed to facilitate FSMC to reduce a large number of fuzzy rule bases and to select optimal control gains, respectively. In the second phase, the FNNC is developed, which is, compared to the FSMC, easier to design the control rule, more robust against environment and capable of on-line learning. Numerical simulations are conducted and the comparison between various controllers is made based on simulations. The simulated results show that the transverse vibration can be well suppressed by both approaches. FSMC offers the capability to regulate the transient response, while FNNC holds advantage of on-line learning capability.     

相位补偿算法对提高太赫兹雷达距离像分辨率的研究

介绍了0.2 THz频率步进雷达系统以及获得一维距离像的方法,并利用0.2 THz雷达对角反射器进行距离像分辨率实验,分析了频率步进信号相位不一致对一维距离像以及分辨率的影响,提出了回波相位补偿的方法.经过相位补偿后,目标距离像分辨率和信噪比都显著提高,分辨率达到了厘米量级.仿真和实验结果表明,宽带太赫兹频率步进雷达经过相位补偿,可以对目标进行高分辨率成像,从而为太赫兹雷达二维和三维成像奠定了基础.     

基于波变量补偿的阻抗匹配时延双边遥操作

通信时延是遥操作系统中固有的问题,它会严重影响遥操作的性能,降低系统的稳定性和跟踪性。基于无源理论的波变量法可以保证遥操作系统在任意时延下稳定,是解决时延问题的一个重要方法。然而,波变量法带来的波反射会阻扰有用信号的传输,降低了主从端信号的跟踪性,严重时甚至会导致整个系统振荡。针对这一问题,提出了一种基于波变量补偿的阻抗匹配双边遥操作系统结构,旨在减少波反射,提高操作者的临场感和系统的跟踪性。通过仿真实验,结果表明所提方法能够保证固定时延条件下遥操作系统的稳定性,并具有较好的跟踪性。     

泵浦光和信号光之间的相位漂移对级联PSA光传输系统传输性能影响的研究

本文研究相敏光放大器(PSA)中泵浦光相位不能完全跟踪信号光相位时,即两者之间存在相位漂移时,对以PSA作为光中继放大器的高速光纤通信系统传输性能的影响.通过计算机系统仿真,我们得到在不同的相位漂移下,高速信号脉冲眼图劣化度随光纤色散变化的曲线,以及不同传输速率下信号眼图劣化度随放大器相位漂移量变化的曲线.由仿真结果可知,如相位漂移控制在一定范围内,其对系统性能几乎没有影响.但超出此范围时,则系统性能迅速劣化.     

基于高速移动通信的虚拟天线阵列理论研究

在高速移动通信中, 多普勒频移对通信性能产生严重的影响, 通常需要对接收信号的多普勒频移进行估计并进行补偿. 本文研究在对单个天线接收的高速移动通信信号进行频移估计和补偿的基础上产生多路无频偏的信号, 并虚拟为天线阵列的输出以提高系统的接收增益. 首先讨论了“均匀时间采样”和“均匀相位采样”的关系, 并根据两者之间的关系提出了补偿多普勒频移和虚拟天线阵列的算法, 即对采样信号进行插值、均匀相位抽取以后, 再进行均匀时间采样. 然后分析了算法对高速移动通信系统性能的改善作用, 并提出了算法的硬件实现结构. 通过数值仿真验证了算法的干扰抑制能力和误码性能, 结果表明本文提出的虚拟天线阵列算法能够改善飞机、高铁上的高速移动通信系统的性能.     

M元混沌扩频多通道Pattern时延差编码水声通信

Pattern时延差编码水声通信体制利用信息码元的时延值调制信息，他的抗多途扩展干扰能力与码型种类及码型脉宽有关. 扩频通信可获得扩频增益，可胜任远程水声通信，但其通信速率低是使用受限的重要原因. 提出将扩频通信与Pattern时延差编码水声通信体制相结合，并采用M元扩频、多通道工作方式，构成一种新的适用于水声环境的通信方案，既可获得扩频通信的优良性能，又可提高通信速率. 湖试结果验证了本文提出的M元混沌扩频多通道Pattern时延差编码水声通信方案的鲁棒性及可行性.