长距离分布式光纤传感中基于STM32的遗传算法偏振控制

基于STM32微处理器采用偏振控制器反馈技术并结合遗传算法对50km长距离分布式光纤振动传感系统中偏振衰落进行抑制.结合STM32与PCD-M02型偏振控制模块特性,优化遗传算法相关参量,在STM32微处理器上实现了遗传算法对传感系统的偏振控制.实验结果表明,基于STM32微处理器的遗传算法在短时间内能得到全局近似最优解,有效实现偏振控制,该方案适用于对实时性和集成度要求较高的长距离分布式光纤传感系统.     

拉曼光谱退偏度实验的设计与研究

为了研究拉曼光谱偏振特性,设计了5种测量拉曼光谱退偏度的实验方案,得到实验和理论相吻合的结果,比较分析了不同实验方案的区别。     

拉曼光谱偏振特性的研究

在研究拉曼光谱偏振特性的基础上，计算出四氯化碳(CCl4)样品各简正振动模式的退偏度，设计了测量拉曼光谱退偏度的实验方案，并得到理论和实验相吻合的结果。     

相位敏感型光时域反射传感系统光学背景噪声的产生机理及其抑制方法

相位敏感型光时域反射(Φ-OTDR)传感系统具有响应速度快、灵敏度高等优点,能够实现对微弱扰动的分布式检测,在重大设施的入侵警戒、大型工程结构的健康监测等领域具有广阔应用前景.然而,与传统的OTDR传感系统不同,Φ-OTDR系统中存在着激光器中心频率漂移、偏振相关的噪声、光纤应变与干涉强度非线性对应关系引起的测量失真等光学背景噪声,对有效信号的提取形成了不可忽视的干扰,从而限制了Φ-OTDR传感系统在实际应用环境下的传感性能.本文对这些光学背景噪声的产生机理进行了深入分析,并提出了相应的噪声抑制方法.实验结果表明,本文提出的方法可以有效抑制Φ-OTDR传感系统中的光学背景噪声,并显著提高传感系统性能.     

偏振光斯托克斯参量的高速实时测量技术

为了满足对高速变化的偏振态的测量,提出一种能够对偏振态实现高速测量的技术。阐述了利用1/4波片与起偏器测量偏振光的斯托克斯参量常规的原理和方法,根据高速测量的要求推导出了新的斯托克斯参量计算公式,并依据此公式设计了基于多通道偏振态高速测量的方案,设计了具体的方法并编写了控制与算法程序。测试表明,该系统的测量速度达到了每秒700次偏振态测量,测量速度主要由电子线路的性能决定,测得的结果稳定可靠实现了光纤传输偏振态的高速测量。     

基于偏振自适应和主动相位控制的相干合成的实验研究

进行了非保偏放大器与保偏放大器的相干合成的实验研究。通过随机并行梯度下降（SPGD）算法对非保偏放大器进行偏振自适应控制,使非保偏放大器输出激光的消光比达到11.5 dB,与保偏放大器在同一偏振方向上的光功率占总功率的93.4%。利用单抖动法进行非保偏放大器与保偏放大器的主动相位控制,实现相干合成。实验结果表明:SPGD算法能够有效实现偏振自适应控制,偏振自适应控制前后相干合成远场的条纹对比度从80.1%提高到87.2%,相干合成的效果提升明显;通过增加参与合成的放大器路数,并在各路激光中引入多级功率放大器,能够得到更高的合成功率输出。     

偏振无关的旋光双反射结构的实验研究

完成了偏振无关双旋光晶体双反射结构的实验研究. 根据其偏振补偿特点对双旋光晶体双反射结构进行简化, 提出了一种偏振无关的单旋光晶体双反射结构. 实验表明, 两种反射结构的偏振保持度均能达到99.97%以上. 作为对比, 分别测试了单个反射镜反射90°和两个反射镜反射90°时的输出光偏振态. 该条件下, 无保偏处理的反射镜的偏振保持度分别只有92.1%和76.2%. 关键词： 偏振态 偏振无关反射 旋光晶体     

白光干涉在保偏光纤测量与对轴中的应用

本文根据白光干涉原理，研究了保偏光纤偏振色散和耦合系数的测量，保偏光纤连接时主轴夹角的调整，并获得了满意的实验结果，还对白光干涉技术在保偏光纤传感和器件方面的应用作了初步的讨论。     

基于斯托克斯矢量的偏振成像仪器及其进展

偏振成像技术将景物的偏振信息转化为二维图像信息,从而可以和灰度图像一样对目标景物进行场景特征分析。介绍了基于斯托克斯矢量的偏振成像原理。按照获取斯托克斯矢量方法的不同,分别介绍了偏振片起偏、偏振棱镜分光和可变延迟波片调制三类分时偏振成像方式,分振幅、分孔径、分焦平面三种同时偏振成像方式。结合我国的制造水平,设计了双CCD渥拉斯顿棱镜同时偏振成像实验系统,并采集了实验图像。分析了各种偏振成像方式的优缺点。指出了偏振激光照明主动偏振成像、光谱偏振成像是偏振成像仪器进一步的发展方向。     

偏振模耦合分布式光纤传感器空间分辨率研究

分析了偏振模耦合原理的分布式光纤传感器的自相干与互相干光；实验测量的干涉光证明了理论分析是正确的；利用偏振模耦合原理传感与白光干涉检测的分布式光纤传感器的空间分辨率是由光纤偏振色散系数与光源的谱宽决定的；由实验测量的偏振模耦合分布式光纤传感器的空间分辨率为6cm. 关键词： 光纤传感器 保偏光纤 空间分辨率 偏振模耦合     

Experimental study of the Raman strain rosette based on the carbon nanotube strain sensor

This work presents a new technique named Raman strain rosette for the micro‐strain measurement of both Raman active and Raman inactive materials. The technique is based on the theoretical model of the carbon nanotube (CNT) strain sensor that applies the resonance and polarization Raman properties of CNTs and calculates the synthetic contributions of uniformly dispersed CNTs to the entire Raman spectrum. In our work, the proposed technique is applied in different experiments on the Raman inactive materials, such as step‐by‐step uniaxial tensile and Raman mapping around a circular hole. The experimental results reached by the Raman strain rosette are consistent with the actual values as a whole. This study verifies that the Raman strain rosette is applicable to quantitative measurement of all the in‐plane components of the strain tensor (including both normal and shear strains) by three polarized Raman detections for each sampling spot on a microscale. The technique is further applicable to achieving the strain fields through Raman mapping. Copyright © 2010 John Wiley & Sons, Ltd.     

Polarization behaviors of twisted carbon nanotube fibers

Polarization behaviors of carbon nanotube (CNT) fibers with different twisting were reported. Scanning electron microscope and polarized Raman spectroscopy were used to investigate the prepared samples. Results indicate that surface twisting angle affects greatly the polarization angle and I_///I_⊥ ratio of twisted CNT fibers. Raman depth profile measurements imply that the twisted fibers consist of non‐uniform CNT alignments. A simplified two‐CNT‐alignment geometric model was proposed to illuminate the experimental observations. The results suggest that polarized Raman depth profile measurement would be a very useful approach for determining the distribution of CNT alignments in CNT fibers. Copyright © 2012 John Wiley & Sons, Ltd.     

A New Theoretical Model of a Carbon Nanotube Strain Sensor

Carbon nanotubes （CNTs） are potential strain sensors due to their excellent mechanical and spectral properties. A new theoretical model of a CNT strain sensor is obtained by applying the polarized Raman properties of CNTs, which calculates the synthetic contributions of Raman spectra from the CNTs in random directions. By using this theoretical model, the analytic relationship between planar strain components and the Raman shift increment of uniformly dispersed CNTs is obtained, which is applicable for accurately characterizing the strain in random directions on the surface of a measured microsystem.     

电场诱导碳纳米管阵列准直生长的研究

在传统的热化学气相沉积(CVD)的基础上,引入针尖电场,开展了电场对碳纳米管阵列准直性改善的研究。利用扫描电子显微镜(SEM)和Raman光谱两种表征手段,研究了加电场与不加电场两种情况下得到的碳纳米管(CNT)阵列的准直性,证明了电场对碳纳米管阵列准直生长的有效性。文章还对电场诱导碳纳米管阵列准直生长的机理进行了初步的探讨,认为电场使碳纳米管极化是CNT阵列准直生长的主要原因。     

Different angle-resolved polarization configurations of Raman spectroscopy: A case on the basal and edge plane of two-dimensional materials

Angle-resolved polarized Raman(ARPR) spectroscopy can be utilized to assign the Raman modes based on crystal symmetry and Raman selection rules and also to characterize the crystallographic orientation of anisotropic materials.However, polarized Raman measurements can be implemented by several different configurations and thus lead to different results. In this work, we systematically analyze three typical polarization configurations: 1) to change the polarization of the incident laser, 2) to rotate the sample, and 3) to set a half-wave plate in the common optical path of incident laser and scattered Raman signal to simultaneously vary their polarization directions. We provide a general approach of polarization analysis on the Raman intensity under the three polarization configurations and demonstrate that the latter two cases are equivalent to each other. Because the basal plane of highly ordered pyrolytic graphite(HOPG) exhibits isotropic feature and its edge plane is highly anisotropic, HOPG can be treated as a modelling system to study ARPR spectroscopy of twodimensional materials on their basal and edge planes. Therefore, we verify the ARPR behaviors of HOPG on its basal and edge planes at three different polarization configurations. The orientation direction of HOPG edge plane can be accurately determined by the angle-resolved polarization-dependent G mode intensity without rotating sample, which shows potential application for orientation determination of other anisotropic and vertically standing two-dimensional materials and other materials.     

基于掺铒光纤/喇曼混合放大的光纤激光器布喇格光栅传感系统

提出了一种提高长距离光纤布喇格光栅信噪比以进行准分布测量的新方法.该方法基于掺铒光纤/喇曼混合放大的光纤激光器结构,掺铒光纤和滤波器构成的环形结构产生激光作为光源,喇曼光纤放大器对布喇格光栅信号进行低噪音的双向放大,置于远处的掺铒光纤利用剩余的泵浦功率产生自发辐射光和放大传感信号,为远处掺铒光纤之后的布喇格光栅传感器提供信号光以及补偿由于长距离传输造成的光纤损耗.实验显示,与使用宽带光源的传感方式相比,系统的性能得到显著提高,仅使用小功率泵浦,分布在50 km光纤上的FBG均获得了超过58 dB的优良信噪比.     

基于喇曼/掺铒光纤混合放大的长距离布喇格光栅传感器系统

提出了一种提高长距离光纤布喇格光栅信噪比以进行准分布测量的新方法.本方法基于双向喇曼放大和双掺铒光纤结构,喇曼光纤放大器对布喇格光栅信号进行低噪音的双向放大,置于远处的掺铒光纤利用剩余的泵浦功率产生自发辐射光和放大传感信号,为第二段掺铒光纤之后的远处布喇格光栅传感器提供光以及补偿由于长距离传输造成的光纤损耗.实验显示传感器系统的性能得到显著提高.使用功率为240 mW的单个普通泵浦,分布在50 km光纤上的FBG均可获得15 dB的良好信噪比,比混合放大前提高了10 dB.     

Evaluation method for Raman depolarization measurements including geometrical effects and polarization aberrations

In this article, we address the notoriously difficult problem to quantitatively link measured Raman depolarization values to theoretical polarizability tensor quantities, since quantum calculations do not incorporate experimental parameters. For this, we introduce a numerical model to calculate, for realistic experimental configurations, effective Raman line strength functions, Φ, which find their way into depolarization ratios, ρ. The model is based on interlinked integrations over the angles in the light collection path and a finite Raman source volume along the excitation laser beam. The model deals also with the conditional aperture parameters, associated with more than one optical component in the light collection path. Finally, we also can take into account polarization aberrations introduced by the sample cell windows. The procedure was fully tested for Raman depolarization spectra of selected hydrogen isotopologues. Distinct aspects affecting Raman depolarization data were validated, namely: (1) excitation polarization impurities; (2) extended Raman excitation volumes; (3) Raman light collection over finite solid angles; and (4) polarization aberrations introduced by optics in the light collection path. The correction of the experimental measurement data for the aforementioned effects resulted in depolarization ratios for the Q₁(J " ) Raman lines of H₂ and T₂, which mostly differed by less than 5% from those obtained by quantum‐calculations. Copyright © 2013 John Wiley & Sons, Ltd.     

柔性固体燃料弹性模量测试的实验研究

利用砝码对柔性固体燃料试件加载,并采用光纤法珀应变传感器对试件进行应变测试;结合砝码重量和测得应变计算出燃料试件弹性模量.测量的标准差为23.04 MPa,在误差允许的范围内,离散度可以接受.实验表明：用光纤法珀应变传感器测量柔性固体燃料的弹性模量是可行的.     

Raman study of InAs/GaAs quantum dot solar cells

We report polarized and resonant Raman study of InAs/GaAs quantum dot solar cell (QDSC) structures. Raman spectra obtained from the top surfaces of the samples suggested that the formation of InAs QDs induced tensile strain in the overgrown GaAs layers. Furthermore, a longitudinal optical phonon-plasmon (LPP) coupled modes were observed in the p-type GaAs layers. The tensile strain was increased with an increase in the QD size. The hole concentrations estimated by fitting the individual LPP coupled modes were in the range of 2.4–3.5 × 10¹⁸ cm^?3. Resonant Raman spectra obtained from the cleaved sides, where the QDs were located, showed a 225 cm^?1 mode in parallel polarization configurations. Based on accurate analysis, this mode was identified as the LA(X) phonon of GaAs.