任意椭圆函数拟合法测量光纤几何参数

无论是通讯光纤还是医用光纤,光纤的几何参数总是评价其质量的重要指标。灰度法是国标GB15972.20-2008中的建议方法,但该方法在拟合过程中会出现拟合圆与椭圆的中心不重合,存在测量原理上的缺陷。且当光纤的切割效果与照明条件发生改变时,往往导致测量数据的不稳定并带来误差。本文用更符合光纤端面实际的任意椭圆函数(非标准椭圆),且仅用这一种函数拟合的方法求取光纤几何参数,从而从根本上消除由圆拟合与椭圆拟合的中心不一致带来的原理缺陷。同时,由于在计算各个参数时不需要图像分布灰度的具体值,从而降低了对测量条件的要求。实验表明,本文方法能有效提高仪器测量结果的稳定性和一致性。     

光纤几何参数自动测量技术

介绍了一种光纤几何参数自动测量的新技术，利用图象扫描和脉冲计数方法获取光纤截面的边缘信息，用微机进行数据采集和处理，有效地提高了测量系统的分辨率和测量速度，实验结果表明：该测量系统的测量重复性达0.1um，分辨率可达0.05um，单个光纤试样的测量时间<1min。     

基于远场可变孔径的贝塞尔函数拟合法求单模光纤模场直径

模场直径作为单模光纤的一个重要参数,远场可变孔径法是GB.15972.45-2008中推荐的测量方法.本文分析了单模光纤中传播光场的分布,其中光场的模式行为是亥姆霍兹方程的解,理论上应满足贝塞尔函数.对此,本文基于远场可变孔径法提出一种利用贝塞尔函数拟合光纤出射光场分布,进而由拟合得到的模场分布曲线计算模场直径.与目前...     

基于机器视觉的光纤端面几何参数测量研究

研究了一种基于机器视觉的光纤几何参数测量方法。该方法运用数字图像处理算法,首先,读取光纤端面图片,采用Deriche边缘检测算法进行图像分割;然后,利用去伪边缘算法完成对有效边缘的提取及合并;最后,进行曲线拟合,完成对光纤端面几何参数的测量。实验结果表明：该方法操作简便,算法复杂度低,光纤端面边缘拟合精确度较高,数据检测速度快,可以精确高效地检测出光纤端面几何参数的数据,对涂覆层直径的重复测量精度可达0.021μm,涂覆层圆度重复测量精度可达0.043%。     

聚合物光纤几何参数测量系统

基于CCD图像技术提出了显微放大成像、图像相对测量，通过计算机图像处理完成外径的为1mm聚合物光纤几何参数（芯径、外径、不圆度）的测量，测量精度为6μm左右。并给出了系统的结构与原理，分析了系统实现的精度保证。该系统也可实现聚合物光纤数值孔径的测量和折射率分布的表征等。     

高斯线法提取传感光纤不规则平面路径研究

高精度分布式光纤传感技术具有超高空间分辨率,可用于高应变梯度的结构形变测量。针对表贴式分布式传感光纤应变监测数据重构中的测点坐标偏差问题,提出一种基于高斯线检测的传感光纤测点坐标序列提取方法。首先利用传感光纤在物体表面所形成的高度差借助方形无影光源从侧面照明提升光纤在物体表面的区分度,采用基于Canny算法的亚像素边缘检测技术获取传感光纤目标区域,并筛选特性去除干扰边缘,最后由高斯线检测方法提取光纤中心路径,进而分段获得实际传感光纤测点坐标值。据实验表明,该文方法能有效去除粘胶等噪点准确检测平面传感光纤,并对其非规则曲线路径进行重构。     

基于高斯拟合的光纤法珀相关解调算法研究

为了提高非扫描式互相关解调系统的解调精度,通过分析非扫描式解调系统的信号特征,研究了一种基于高斯拟合的解调算法.该算法使用最大值寻峰算法解调出峰值位置,提取出峰值位置附近的光强数据,利用高斯函数对提取出的数据进行曲线拟合,提高了解调的精度.仿真结果表明,该算法具有良好的解调稳定性、解调准确性以及一定的抗干扰能力,仿真中...     

光纤参数测试方法的研究

本文概括论述了光纤的测试参数及测试方法及不确定度分析。总结了光纤几何参数、模场直径、截止波长、衰减及波长色散的测试方法和不确定度评定方法。归纳出了光纤参数测试中存在的问题和解决方法。     

径向高斯核函数时频分布及在故障诊断中的应用

对一种可调核函数的时频分布－径向高斯核函数时频分布（RGKD）进行了研究,并将径向高斯核函数时频分布引入机械故障诊断。这种时频分布根据被分析信号不同特性,采用优化方法自适应对模糊函数进行整形,尽可能保留集中在原点的信号模糊函数的自分量,抑制远离原点的交叉分量,与固定核函数的时频分布对比结果表明,径向高斯核函数时频分布极大地去除了交叉分量,提高了分辨率,并且对品怕不敏感,在分析实际低信噪比的信号时,仍能保持较高的分辨率,杂散分量很少,该方法具有对信号的广泛自适应性,试验证明径向高斯核函数时频分布在故障诊断中的较强的特征提取作用。     

单模光纤模场直径标准测量装置的研究

本文讨论一种用于单模光纤模场测量的连续变孔径方法，该方法利用一个圆形光阑沿光纤轴线方向进行远场扫描，测量不同孔径角下的光功率分布，从而得出Petermann-Ⅱ定义的模场直径，与传统的变孔径测量技术相比，该方法具有测量孔径角范围宽、取样点多以及取样角度可以控制等优点，因此提高了测量精确度和拓宽了适用范围，对不同的光纤样品在1.3um和1.55um波长下所作的实验表明，测量不确定度小于3%。     

光纤出射光强分布研究

对多模光纤出射光束的光强分布用横向位移法进行了理论分析和实验研究,并用数值计算的方法分析实验测量数据.结果表明,高斯光束可以很好地描述光纤出射光强的分布,光纤出射光束光强分布参数主要与光纤芯径和出纤光功率等有关,为强度调制型光纤传感器的优化研制提供了必要的实验依据.     

Analysis of output characteristics of the actively Q-switched intracavity optical parametric oscillator considering Gaussian distribution of intracavity photon densities

By considering the Gaussian spatial distribution of the initial population-inversion density and the intracavity photon densities of the fundamental, the signal and the idle lights, the rate equations of a LD-pumped actively Q-switched intracavity optical parametric oscillator (IOPO) are derived. The influence of the pump rate, the thermal effect in the gain medium and the change of the photon density along the cavity axis have also been taken account in the equations. By numerically solving these coupled equations, the dependences of pulse width, pulse energy and peak power on incident pump power for the generated-signal light are obtained. In the experiment, a laser-diode-pumped actively Q-switched Nd:GdVO₄/KTP IOPO with an acousto-optic (AO) modulator is realized and the experimental results agree with the theoretical calculations.     

测量高斯光分布半宽度的光电共轭方法

测量光电信号与参考光电信号来自同一光电器件,形成一对共轭函数。调整参考光电信号 放大器的正电源电平,使之等于测量信号的峰值,此时两函数共轭交点之间的距离即对应于光束的半宽。测量过程中,被测光束能量的缓慢变化并不对结果造成影响,因此稳定性较好,实验重复精度至±2mm。     

InP薄膜内包层光纤放大性的理论计算

将纳米技术和光纤技术相结合，对研制出的纳米级InP薄膜内包层光纤进行光放大性能的测试，测试结果表明该光纤在很短的长度上具有比较好的放大性能，单位长度放大系数在906-1044nm的波段上为1．40-5．12dB／m，在1080-1491nm的波段上为1．40-15．35dB／m，在1524-1596nm的波段上为1．86-7．44dB／m。根据氢原子模型计算了InP微粒产生量子尺寸效应的相对粒径αB=8．313nm，以及纳米级InP微粒的粒径与能级改变的关系得到，当厚度d=16nm，△E=0.071eV,满足当d≤2aB时的强限域，量子尺寸效应明显，光纤具有光放大性,计算结果与实验测试结果相符。     

Analysis and simulation of a fiber optical gyroscope with Shupe error compensated optically

Shupe error, a kind of bias error over temperature-varying environments, still exists even with strict quadrupolar winding pattern, and it affects the environment adaptability of fiber optical gyroscope (FOG) and limits its application. A novel configuration to realize optical compensation for Shupe error in FOG is promoted, employing the opposite polarity of Shupe error in two FOGs working with polarization-maintained (PM) fiber’s fast and slow axis, respectively, in a single PM fiber coil. Analysis is also made for polarization non-reciprocity (PNR) in both FOGs, based on which the optimum coupling angles between integrated optic chip and PM fiber coil are obtained to guarantee that Shupe error arising from both FOGs can be counteracted to zero, and PNR error is suppressed to be minimum at the same time.     

The impact of vertical internals array on the key hydrodynamic parameters in a gas-solid fluidized bed using an advance optical fiber probe

The effect of a circular configuration of intense vertical immersed tubes on the hydrodynamic parameters has been investigated in a gas-solid fluidized bed of 0.14?m inside diameter. The experiments were performed using glass beads solid particles of 365?μm average particle size, with a solid density of 2500?kg/m³ (Geldart B). An advanced optical fiber probe technique was used to study the behavior of six essential local hydrodynamic parameters (i.e., local solids holdup, particles velocity, bubble rise velocity, bubble frequency, and bubble mean chord length) in the presence of vertical immersed tubes. The experimental measurements were carried out at six radial positions and three axial heights, which represent the three key zones of the bed: near the distributor plate, the middle of the fluidizing bed, and near the freeboard of the column. Furthermore, four superficial gas velocities (u/u_mf?=?1.6, 1.76, 1.96, and 2.14) were employed to study the effect of operating conditions. The experimental results demonstrated that the vertical internals had a significant effect on all the studied local hydrodynamic characteristics such that when using internals, both the solids holdup and bubble mean chord length decreased, while the particles velocity, bubble rise velocity, and bubble frequency increased. The measured values of averaged bubble rise velocities and averaged bubble chord lengths at different axial heights and superficial gas velocities have been compared with most used correlations available in the literature. It was found that the measured values are in good agreement with values calculated using predicted correlation for the case without vertical internals. While, the absolute percentage relative error between the measured and calculated values of these two hydrodynamic parameters indicate large differences for the case of vertical internals.     

Determining the double‐K fracture parameters for three‐point bending notched concrete beams using weight function

Parameters of universal form of weight functions having four terms and five terms are derived for edge cracks in finite width of plate. The standard Tada Green's function is taken as the basis for the derivation. The shape of universal form of weight functions considered enables closed form expressions for cohesive toughness of three‐point bending test geometry of notched concrete beams due to linear cohesive stress distribution in the fictitious fracture zone. This solution provides a viable method to determine the double‐K fracture parameters: the initiation toughness, and the unstable toughness for mode I fracture of concrete beam. A comparison with existing analytical method shows that the weight function method for determination of the double‐K fracture parameters yields results without any appreciable error. The use of weight function will not only simplify the calculation to obtain the double‐K fracture parameters, and but also it will avoid the need of skilled numerical integration technique due to singularity problem at the integral boundary.     

Novel fabrication of nano-pattern with optical function by selective doping of dye vapor into novolac resin

We report selective doping of vapor of yellow dye, ferrocenedimethanol into exposed (UV-irradiated) areas of novolac resin films. When vapor of the dye was contacted with micro-patterned resin films containing both exposed and unexposed areas, the dye was doped only into the exposed areas, resulting in fabrication of micro-pattern containing the dye. On the contrary, ferrocene and other ferrocene derivatives were doped both exposed and unexposed areas of the resin. A contact angle measurement of aqueous drops on each dye indicated that the chemical affinity between hydroxyl groups of ferrocenedimethanol and exposed areas of the novolac resin will enhance selective doping of the dye into the exposed areas.     

Effect of system parameters on size distribution of 304 stainless steel particles produced by electrical discharge mechanism

An electrical discharge machine (EDM) can be used to produce Uranium Carbide (UC) microspheres. This material is useful for dispersed nuclear fuel fabrication. To obtain empirical data about the process parameters for UC modeling, 304 stainless steel (304 SS) was used to produce microspheres. Particle size effects were analyzed via three parameters; arc intensity, dielectric medium, and pulse width. Results indicate that the size and yield of the particles are dependent on all three parameters. The yield of larger particles increased with increasing arc current. Particle size distribution decreased with decreasing pulse width.