【作者】 唐锋；

【导师】 张以谟； 周革；

【作者基本信息】 天津大学 ， 光学工程， 2005， 博士

【摘要】 基于白光干涉原理,研制成功高双折射保偏光纤分布式偏振耦合测试仪一台。该仪器用于保偏光纤偏振模式能量耦合现象的检测,可作为保偏光纤制造及使用过程中的一种有效检测手段,提高光纤偏振器件及系统的性能。在继承课题组原有工作的基础上,从理论、仪器化、实验和应用四个方面对偏振耦合及白光干涉技术进行深入研究。理论分析了外部扰动与保偏光纤双折射、偏振耦合间的数学关系;分析了方案本身、偏振模式、仪器客观条件等对干涉结果的影响,给出了消除干涉仪系统误差的耦合强度和耦合点位置计算方法;设计完成了仪器的光学、机械、电路、数据处理及软件系统,仪器可完成500m长保偏光纤的干涉扫描,无双折射色散下空间分辨率和耦合强度探测灵敏度分别达到6cm和-80dB。基于该仪器,开展了保偏光纤环测试等一系列应用研究。工作中的主要创新点:1.根据模式耦合理论、光弹理论及弹性力学理论,建立了外力作用下三段保偏光纤串联的偏振耦合模型,揭示了保偏光纤受扰动区双折射轴的旋转是偏振耦合的来源;建立了力场大小、方向和作用长度与偏振耦合的数学关系,并将其应用于分布式应力传感。2.首次阐明了保偏光纤双折射色散对偏振耦合测试的影响,从理论和实验上说明了由于双折射色散的作用,随着光纤长度的增加,白光干涉包络展宽及干涉可见度下降的规律。3.分析了偏振激发模式对偏振耦合测试的影响,提出了任意偏振态激发的测试方案;采用偏振调整优化,提高耦合点干涉条纹的可见度,将仪器耦合强度探测灵敏度提高10dB;提出了基于检偏器透射光的偏振调整系统,直接旋转格兰棱镜消除系统波长相关性。4.在分析偏振耦合测试白光干涉数据时频特性的基础上进行了其处理算法开发:小波变换去噪,时频分析耦合点自动识别,非线性回归分析干涉包络提取。5.基于偏振耦合测试仪,开发了保偏光纤环检测、偏振无源光器件检测、保偏光纤对轴、保偏光纤拍长测试、分布式传感、保偏光纤双折射色散检测等多种应用。更多还原

【Abstract】 An instrument measuring the distributed polarization coupling in high birefringence polarization-maintaining fiber (PMF) is developed based on white light interferometry. The instrument is used for the detection of distributed polarization mode coupling point in PMF. It can be used as an effective testing tool in PMF manufacture and applications. The performance of optical fiber polarization devices or systems can be improved significantly.Based on previous work of our lab, further study has been done in the system theory, instrumentation, experiments and applications. The relationship between external perturbations and PMF’s birefringence, polarization coupling is deduced mathematically. The influence of the scheme itself, polarization modes, state of the instrument on the interference results are analyzed and a calculation method is put forward free of the system error for the obtain of coupling intensity and coupling point position. The system optics, mechanics, hardware, data processing and software had been designed and realized. When the fiber under test has no birefringence dispersion, a length of 500m PMF can been scanned with spatial resolution of 6cm and coupling intensity detection sensitivity less than–80dB. Based on the instrument, a series of applications are developed including PMF ring testing and so on.Major innovations of this dissertation:1. Based on mode coupling theory, principle of photo elastic and elasticity, a concatenation of three PMF sections is used to model the polarization coupling phenomena. It’s revealed that the rotation of the principle axes of perturbed PMF is the source of polarization modes coupling. The relationship between the coupling intensity and the amplitude, direction, and the acting length on the fiber of the force is clarified. And the phenomenon is applied in the field of distributed stress sensing.2. The influence of the birefringence dispersion on polarization coupling test is illustrated for the first time. The role of birefringence dispersion is clarified theoretically and experimentally. As the increasing of fiber length, the interference packet envelope is broadened and the interference contrast becomes worse.3. The influence of exited state of polarization (SOP) on the polarization coupling testing is analyzed, testing method with random polarization state exited has been proposed. Using optimized polarization projection angle, the interference fringe contrast can be improved, and the polarization coupling intensity testing sensitivity can be improved 10dB. A polarization adjusting mechanism is realized based on the transmission light of the analyzer, and the wavelength dependency of the polarization adjusting system is avoided by rotating the Glan prism directly.4. After grasping the time-frequency property of the scanning white light interference data, a group of algorithm are put forward for the detection of polarization coupling point in PMF, including wavelet de-noise, coupling point automatically recognition using time-frequency region analysis, and white light interference envelope extraction using nonlinear regression.5. Based on polarization coupling principle and the instrument has been developed, six applications of testing of PMF ring and polarization passive components, principle axes alignment of PMF, beat length measurement, distributed sensing, and charactering birefringence dispersion of PMF have been realized.更多还原