色散线性度可调的大啁啾FBG色散补偿器

针对传统大啁啾FBG色散补偿技术中色散曲线线性度难以控制的问题,分析了相对啁啾系数比值与色散线性度之间的关系,依此提出一种基于大啁啾FBG的中继色散补偿器设计方案.该补偿器通过调节一阶和二阶啁啾系数的比值,实现色散曲线线性度可调的功能,且具有补偿带宽范围大、适合WDM系统远程中继补偿的特点.将该设计作为中继补偿器配置在500 km、8通道WDM系统中进行模拟实验,论证了该补偿器的效果.     

Broadband second-harmonic generation in a tapered PPLN waveguide

We demonstrate a period poled tapered lithium niobate waveguide and study second harmonic generation (SHG) in this device for the purpose of broadening the quasi-phase matching (QPM) acceptance bandwidth. The finite-difference beam-propagation method is used to simulate the guided modes and calculate the effective indices. The simulation results show that by tapering the width of the cross section linearly, the phase mismatch between a specific input wavelength and its SHG signal can be varied along the propagation length. Ideal SHG phase-matching conditions for a wide range of input wavelengths in communication band from 1 542.5 nm to 1 553.5 nm can be satisfied in different positions of the waveguide.     

Efficiency enhancement for the orbital angular momentum photon quantum interface via single photon frequency upconversion

As the application of orbital angular momentum (OAM) of photon quantum in quantum communication, the OAM photon quantum interface for the transmission wavelength from the telecom communication quantum information storage in visible regime is required. Here we demonstrate the efficiency enhancement for the OAM photon quantum interface based on the frequency upconversion from telecom wavelength to visible regime by sum-frequency generation. The infrared photons at 1 558 nm carrying different OAM values could be converted to the visible regime at 622.2 nm with the optimal efficiency via adjusting the pump beam waist radius and intensity.     

基于PPMgOLN绿光微片激光器的散斑抑制

提出了一种将激光耦合入多模光纤后,利用改变多模光纤长度并结合振动光纤的方法来抑制散斑的方法。介绍了抑制散斑的相关理论及实验验证方法。实验中采用自主研发的基于PPMgOLN晶体的高效紧凑型微片绿光激光器作为激光光源,经过CCD相机采集屏幕上的散斑图像,通过图像处理,得到了相同型号的多模光纤在不同长度下,光纤在振动与不振动时,图像散斑对比度的变化趋势及在屏幕上的强度分布,从理论上分析了产生该变化趋势及强度分布情况的原因。实验所得的图像散斑对比度在4.7％左右,满足视觉观察的要求。     

基于Web的地图服务引擎的设计与实现

论文结合实时栅格地图渲染引擎和矢量地图发布引擎的优点,提出一种新的基于Web的地图服务引擎的设计方案和实现过程,并采用栅格地图预渲染入库的方式,显著地改善了引擎的性能和完善了引擎的功能.采用该引擎的GIS系统已经应用于视频监控系统中,效果良好.     

Nondestructive characterization of the domain structure of periodically poled lithium niobate crystal based on rigorous coupled-wave analysis

We report rigorous coupled-wave analysis (RCWA) method to non-destructively characterize the domain structure of periodically poled lithium niobate (PPLN) crystal. The strong light diffraction effect is achieved by applying a proper external voltage. We can observe reversed domain pattern and employ the detected diffraction intensity to optimally fit the result of RCWA based on least square method. Compared with conventional scalar diffraction theory, more accurate domain structure parameters with accuracies of 0.05 µm and 0.005 for the period and duty cycle are obtained respectively. It is proved that accurate, real-time and nondestructive characterization can be realized via this method. This work has been supported by the National High Technology Research and Development Program of China (No.2013AA030501). E-mail:wgl@fjirsm.ac.cn      

基于自反馈Hopfield网络的快速文本分类器

根据大规模中文文本分类的特点,提出了一种基于最大特征值选取的快速文本正交编码方法,并构造了一种具有较快收敛速度的Hopfield神经网络模型.采用神经动力学方法,对自反馈Hopfield神经网络的网络结构进行了稳定性分析.在Hopfield神经网络中引入KNN再预测机制,使进入伪状态而被拒收的样本能有效地逃离伪状态.实验结果表明,该方法应用到大规模的中文文本分类时,效果良好.     

周期性极化掺镁铌酸锂晶体光参量振荡研究

为了实现高转化率3m红外激光光参量振荡输出,采用外加脉冲电场法在厚度为1mm、掺摩尔分数为0.05的镁铌酸锂晶体上成功制备了周期为31.2m的极化光栅,理论计算并模拟了1064nm激光抽运周期极化铌酸锂晶体时,闲频光波长随温度的对应关系,并进行了实验验证。利用1064nm声光调Q Nd:YAG激光器作为抽运源对样品进行了光学参量振荡实验,其中,脉冲激光脉宽为200ns,重复频率是20kHz。在控制温度为80℃、输入抽运光功率为5.567W时,光参量振荡输出波长3m的闲频光功率为1.141W,光光转换效率达到20.1%。结果表明,通过此方法制备的周期性极化铌酸锂晶体光参量振荡,具有较高的光光转换效率。     

人脸指纹门禁系统的设计与实现

人脸指纹门禁管理系统的实现,能有效地解决传统门禁系统的不足之处.本文介绍了该门禁系统的设计与实现方案.该系统把人脸识别,指纹识别和手机短信验证三种方式结合起来.系统由门禁识别器和服务端软件两部分构成.门禁识别器基于嵌入式系统,通过网络进行互联,服务端基于J2EE架构,实现对识别器的管理.目前,该系统已经投入重要机房门禁系统的实际应用,效果良好.