光纤偏振器件与组件的分布式串音测量研究进展

偏振串音是指光纤偏振器件与组件中两个正交偏振传输模式之间在微扰点发生的能量相互耦合的现象，而沿传输方向串音的连续分布既能够直接反映其光学偏振性能，如起偏、椭偏、消偏等特性，也能间接反映其制备工艺和外部环境状态，如连接与固定处的应力和应变、温度状态等。因此，偏振串音是光纤偏振器件与组件的固有性能和环境影响的综合体现，有望发展成为在线测试、诊断评价光纤偏振器件与组件性能的通用特征参量。基于白光干涉原理的光学相干域偏振测量(OCDP)技术是实现分布式偏振串音检测的最优方法，它利用扫描式白光干涉仪实现不同偏振模式间的干涉，对分布式串音发生的空间位置及幅值强度进行精确测量，具有超高灵敏度、超大动态范围、超长测量长度等优点。本文以光纤偏振器件与组件——保偏光纤环和多功能集成光学调制器作为分布式偏振串音精确测量与应用的范例，介绍了基于OCDP技术的分布式串音测试原理，回顾了测量误差的来源及相应的抑制方法，如由测试光路的参数非理想引入的静态误差以及由测试环境变化引入的动态误差，展示了不同环境温度下光纤偏振器件与组件的精确测试结果。最后，结合光纤偏振器件与组件复杂多变的工作环境，对分布式串音测量方法的发展进行了展望。

Recent progress of accurate measurement for distributed polarization crosstalk of fiber optic polarization component and device

The polarization crosstalk of a fiber optic polarization component and device refers to the optical power coupling that occurs at a disturbance point between the two orthogonal polarized modes propagating in it. The distributed polarization crosstalk along with the light propagation direction is directly responsible for the optical polarization properties, for example, the polarization, elliptical polarization, and depolarization properties. It also indirectly reflects the manufacturing technique and the state of the ambient environment, for example, the stress and strain at the joint and fixed position, as well as the temperature. Thus, it is the comprehensive embodiment of the intrinsic performance of the fiber optic polarization component and device and the influence of environment. It is expected to be a general characteristic parameter for online testing, diagnosis, and evaluation of the performance of the fiber optic polarization component and device. The best measurement method for distributed polarization crosstalk till now is the optical coherence domain polarimetry (OCDP). It is based on the white light interferometry and accurately measures the position and amplitude of the distributed polarization crosstalk using a scanning white light interferometer to realize interference between different polarized modes. It has the merits of ultrahigh sensitivity, ultra-wide dynamic range, and ultra-long measurable length. This review paper takes the polarization maintaining fiber coil and multifunctional integrated optical modulator as examples of distributed polarization crosstalk measurement and application. Firstly, the measurement principle of distributed polarization crosstalk based on the OCDP is introduced. Secondly, the measurement error sources and corresponding suppression methods are reviewed. Thirdly, the accurate measurement results of the fiber optic polarization component and device at different temperature are demonstrated. In the end, it outlooks the development of distributed polarization crosstalk measurement considering the complicated and changeable operation environment of the fiber optic polarization component and device.