应用BISPEC光纤拉制保偏耦合器的研究

设计新颖的ＢＩＳＰＥＣ光纤可避免偏振轴对准技术难点，研制成功高性能保偏光纤耦合器，偏振串扰小于－２５ｄＢ。     

保偏光纤定轴技术的仿真及实验分析

根据保偏光纤侧视成像定轴原理,应用光线追迹方法,分析了保偏光纤侧视成像定轴过程,模拟考察了熊猫型保偏光纤侧视成像的光强分布与偏振轴方位角及物平面位置的关系.对比仿真结果和实验观测结果,对五指型光强分布特征值判断法进行了改进.比较了透镜效应侧视成像的不同定轴方法,发现改进的五指型光强分布特征值判断法的特征值在90°位置附近具有更高的定轴精度,更易于实现保偏光纤偏振主轴的定位.这种方法适用于制作保偏光纤耦合器和保偏光纤偏振器时,在偏振主轴0°或90°方位角时的高精度定轴.     

数字化扫描干涉仪用于保偏光纤偏振耦合检测

首先简要介绍了保偏光纤及其主要参数:模式耦合系数、拍长、偏振消光比和偏振串音等,并给出这些参数的定义和表达式;评价保偏光纤性能的拍长、模式耦合系数、偏振串音等参数也都与偏振耦合相关.讨论了偏振耦合测试技术,对成功应用于保偏光纤测试的波长扫描干涉法等七种方法作了比较.采用"白光"Michelson技术实现了光纤的寄生偏振耦合点空间分布位置测试仪,以该仪器完成了保偏光纤环扫描;偏振无源光器件测试;保偏光纤对轴;保偏光纤拍长测试;分布式(应力、位置、温度)传感;保偏光纤双折射色散测试等.并以保偏光纤环扫描为例给出实验结果,证明了仪器设计理论和实验结果的相符合性.     

单偏振双波长非保偏有源掺杂光纤激光器

利用宽带保偏光纤光栅(PFBG)、普通有源光纤和窄带普通光纤光栅构成独立的谐振腔,且窄带普通光纤光栅的中心波长分别与保偏光纤光栅的一个反射峰波长对准,可以输出稳定的双波长/单波长的单偏振激光.利用这一思想,制成了基于非保偏有源掺杂光纤的单偏振双波长光纤激光器.实验结果表明,双波长同时激射时的激光消光比为46.7 dB,单波长激光的消光比为59.6 dB,滤波出单波长测量其偏振度为98.5%.这种激光器在微波光子领域可用于在光域产生微波.     

基于声光效应的相干光探测方法的研究

基于布拉格衍射和相干光探测原理,分析了入射光和衍射光的特性及数学关系,讨论了如何利用声光偏转器实现信号处理的方法.从改善空间相干光探测效率出发,提出一种将空间光经声光衍射后注入保偏光纤的处理方法,克服了传统相干探测中光偏振态难控制的缺点,减小了外界环境对信号光和参考光合路的影响,降低了光学系统的调整环节中的难度,有效地解决了相干光探测中光束对准和偏振光的保持问题.实验证明,在保证一定的耦合光孔径和激光注入效率条件下,将空间光注入保偏光纤,削弱了背景光对合路产生的影响,使信号光和参考光偏振态和传输方向能更好保持,极大改善了空间相干光探测效率,提高了光电探测信噪比.     

基于波长扫描调制法测量保偏光纤的偏振特性

分析了保偏光纤偏振特性及其拍长和偏振消光比的基本测量原理,并根据单模保偏光纤基模的2个正交偏振模分量HEx11与HEy11间的相位差与波长的关系,推导出偏振拍长的测量关系式,提出了测量保偏光纤偏振特性的波长扫描调制法.采用此方法对熊猫型保偏光纤(YOFC-3367WY)的偏振特性进行了验证性实验研究.拍长和偏振消光比的测量结果表明,在该保偏光纤工作波长处试验结果与理论分析相当一致,说明该方法具有简单易行、测量精度高的优点.     

基于五指型光强分布的保偏光纤定轴方法

保偏光纤偏振主轴的精确定位是保偏光纤应用中的关键技术之一。文中在观察到保偏光纤侧视图像的光强分布呈五指型的实验基础上,提出了一种用于保偏光纤定轴的新方法,即五指型光强分布特征值判断法。实测表明,用于保偏光纤定轴时,在0°附近,与现有的其它定轴方法相比,五指型光强分布特征值判断法的特征更明显,提高了定轴的灵敏度。此新方法可用于制作保偏光纤器件时,在0°附近的高精度定轴。     

基于Faster R-CNN的保偏光纤偏振轴检测方法研究

针对基于端面成像的偏振轴检测方法光照鲁棒性不强、无法同时检测多根保偏光纤偏振轴的问题,提出一种基于Faster R-CNN的检测方法.训练Faster R-CNN神经网络模型,通过参数调优增强了应力区识别的鲁棒性,采用基于Zernike矩算法对应力区边缘点进行亚像素级定位以提高测量精度,分析了测量精度与误差的关系.仿真与实验表明,该方法的测量精度达到±0.1°,在增强光照鲁棒性的同时实现了对多根保偏光纤偏振轴的检测.     

掺铒保偏光纤的技术现状

本文介绍了掺铒保偏光纤的基本结构，制造方法，分析了掺铒保偏光纤的增益特性，保偏特性，增益和偏振间的相互关系，最后介绍了保偏光纤的接续技术。     

铌酸锂光波导器件保偏尾纤对轴工艺研究

基于采用退火质子交换工艺制备的铌酸锂光波导器件的保偏尾纤具有高偏振消光比这一特性,提出了一种通过偏振消光比测试仪测定器件保偏尾纤的偏振轴并实现与保偏连接头定位键高精度对准的方法.工艺实验证明,采用该方法制作的保偏尾纤连接头偏振轴向对准精度优于0.8°,显著优于显微成像定轴方法制作的保偏尾纤接头.     

Reproducible fabrication method for polarization preservingsingle-mode fiber couplers

The adaptation of the biconically-tapered-fused (BTF) fiber coupler fabrication approach to polarization preserving fiber couplers is reported. Two practical methods for identifying and aligning the birefringent axes of the fibers forming the coupler are described. The fabrication approaches are highly reproducible and the 3-dB couplers fabricated exhibit less than 1.0-dB insertion loss, controllable splitting ratio, and an average polarization extinction ratio of 15 to 20 dB     

双轴光纤光栅及其传感应用

简要介绍和分析了保偏光纤及双轴光栅的性质，研究了双轴光栅用作传感器的基本原理，介绍了它在三维应变测量、横向负载测量及双折射光纤拍长测量方面的应用。     

Fabry-Perot cavities with birefringent single-mode fibers and theirapplications as polarimetric sensors

The fields and resonance conditions of Fabry-Perot (FP) cavities containing several birefringent single-mode fibers are analyzed in terms of the fiber birefringence and misalignment of birefringent axes. For FP cavities with birefringent materials, two sets of fringes, corresponding to two cavity modes, are observed. Information is extracted from the separation between adjacent peaks of cavity modes of the same polarization as well as those of different polarizations. Thus an FP cavity containing birefringent fibers can be used as an optical-fiber polarimetric sensor without the use of polarization analyzers. Polarimetric sensors of this type are constructed and tested. The change of fiber birefringence due to a lateral stress applied to low-birefringence fibers is measured and the experimental results are shown to be in good agreement with the theoretical estimates     

Technique for controlling the internal rotation of principal axesin the fabrication of birefringent fibers

The fabrication of a polarization-maintaining fiber in which the internal rotation of the principal birefringent axes was monitored and controlled to a rate of less than 0.1°/cm is discussed. This represents an order of magnitude improvement over the lowest rotation rate observed in commercial fibers. The technique is based on a novel method of interpreting the backscattered power from a-side illuminated birefringent fiber to determine the internal orientation of the strain inducing axes     

Birefringent splittable composite (BISPEC) fiber andpolarization-maintaining couplers

A novel technique for the fabrication of birefringent splittable composite (BISPEC) fiber is reported. We describe in details the design consideration, practical fabrication, and characterization of this fiber. The distinctive feature of this fiber is that the principal axes of the constituent fibers can be accurately aligned in the preform stage so that long lengths of well-aligned fiber can be drawn. We further demonstrate the application of this fiber by fabricating a polarization-maintaining coupler by simply introducing a local taper. Measurements show that such a coupler can have polarization extinction ratio as large as 31 dB (in the best case)     

扭转椭圆双折射光纤环形腔输出特性

对扭转椭圆双折射光纤环形腔的带阻输出特性进行了分析和计算。结果表明，任意椭圆偏振态输入，光纤的双折射和扭转使光纤环形腔带阻输出特性中的谐振峰分裂为两组，对应于光纤的两个本征偏振态。谐振频率发生偏移，偏移量取决于光纤的双折射参数和扭转速率，两组谐振峰的相对幅度取决于光纤的双折射参数、扭转速率和输入偏振态。若输入偏振态为双折射光纤本征偏振态之一，就仅出现一组谐振峰。光纤的双折射和扭转对环形腔的精细度没有影响。     

利用双轴光栅动态称重的初步研究

分析了保偏光纤和双轴光纤光栅的特性,讨论了以双轴光栅为传感元件的压力盒的制作及性能,提出了一种利用双轴光栅的双波峰波长差测量横向负载的方法,并给出了一种汽车动态称重(WIM)轴重仪的设计方案.     

Polarization-dependent parametric and Raman processes in abirefringent optical fiber

The generation of new frequencies by the parametric four-photon mixing process, stimulated Raman processes, and subsequent stimulated mixing processes, all of which arise from the third-order nonlinearity in a single-mode birefringent fiber, is reported. It is observed that different processes are dominant for different input pump polarization angles with respect to the birefringence axes of the fiber. By examining the evolution of the nonlinear output spectra at various input pump power levels for different polarization angles, the pump-polarization-dependent third-order nonlinear processes are studied in detail. The effect of the birefringence-compensated group-velocity matching between the pump and parametric frequencies of different polarizations results in effective nonlinear interactions over long distances for the picosecond pulses     

Nonlinear propagation and self-switching of ultrashort opticalpulses in fiber nonlinear directional couplers: the normal dispersionregime

The propagation of short optical pulses in a nonlinear directional coupler operating in the normal dispersion regime is investigated. The specific example of a birefringent periodically rocked fiber filter where coupling occurs between the two orthogonally polarized modes that are aligned with the birefringence axes of the fiber is considered. In the simulations, a bell-shaped input pulse is injected into one polarization mode: for different input peak powers, the energy present in the same mode at the output of a coupler, which is one or two coupling lengths long, is calculated. The nonlinear temporal broadening, due to the combined effect of group velocity dispersion and self-phase modulation, sets a fundamental lower limit to the time width of the input pulses. When pulses shorter than this critical value are used, the power-dependent energy switching characteristics of a device one coupling length long gets substantially spoiled. Effects related to the finite spectral bandwidth of the fiber filter are discussed. Numerical simulations are compared to recent experimental results on the self-switching of picosecond pulses in the visible (615 nm) with a birefringent rocking fiber