由偏振标记，由光纤远程柔性、共路传输的二合一固体微片激光回馈干涉仪

The microchip laser feedback interferometer our group invented has been used by domestic and international universities and companies. All of the users speak highly of our instruments. The new requirements for improving such instruments mainly focus on the realization of flexible transmission and measurement based on optical fibre, which can enable such interferometers used in very narrow space,break through the limitations of traditional methods where the light signal from the interferometer is linearly projected on the surface of the target and no obstacel is allowed in the optical path. The challenges include avoiding changes of fiber's inner structure caused by the bend of fiber, the change of environmental temperature and stress,which lead to measurement errors. The principle innovation of this work is using two identical microchip lasers placed in parallel. The parallel laser beams go through a calcite crystal and become three light beams. The middle one contains a pare of light beams with orthognal polarizations, named as orthogonally-polarized light. The orthogonal light's frequencies have a Ω shift after going through two acousto optic frequency shifters. The light from frequency shifter is coupled into polarization maintaining optical fiber. On the output side of fiber, a polarization splitter is used to separate the orthogonally-polarized light beams. Because of the polarization splitter, reference light is reflected by reference target and carries reference signal which contains chaos of light path. Measurement light is reflected by the target and caries measurement signal which contains both chaos of light and displacement information of the target. The difference between reference and measurement lights is the displacement information of the target to be measured. The orthogonal light beams are back into lasers and amplified for several orders of magnitude. Feedback interference can only happen between one laser and its light, so two microchip lasers' interference will have no crosstalk. The goal of this research: high resolution in the order of nanometer, long transmission of 50 m using optical fiber, frequency stabilization of 10^-7.

课题组的微片激光（ML)回馈干涉仪，获国内外高度评价和多方应用。新需求：摆脱测量光直射被测目标的惯例，实现光纤柔性传输测量，适应狭小空间应用。挑战：大距离传输时温度、弯曲、外压力等引入的光纤长度变化会掩盖被测位移，使仪器失效。光纤难改，唯靠原理及系统创新：使用一对ML且其光束平行射入方解石，出射光为空间重合的平行(∥)和垂直(⊥)偏振光。光束穿过两个声光移频器后被移频1Ω，后耦合进长距离保偏光纤并传至尾端的格兰棱镜，∥和⊥光分离；∥光被反射回光纤再回ML内，只含光路内噪声信息;⊥光射向被测目标并携目标位移信息返回光纤再回到ML内，它同时含有光路噪声和目标位移信息；∥和⊥光都进入两激光器，光强被放大几个量级。因激光器内干涉只发生在同一激光器的出射光和回馈光之间，∥和⊥光不串扰；从⊥光的总相位改变中减去∥光的相位改变，留者仅为目标位移。预达指标：纳米分辨率，50米光纤，稳频精度10^-7。

课题组经过4年的努力，取决了重要创新成果。 .1、本成果率先使用一对(不是习惯的一个)微片激光器，且他们发射的光束平行射入一片方解石，出射光为空间重合的平行和垂直偏振光。两光束穿过两个声光移频器后被移频1Ω，后耦合进长距离保偏光纤并传至尾端的格兰棱镜将平行和垂直偏振光分离；平行光被反射回光纤，再回到微片激光器内，只含光路内噪声信息;垂直偏振光射向被测目标并携目标位移信息返回光纤再回到微片内，它同时含有光路噪声和目标位移信息；两光光都进入两激光器，光强被放大几个量级.2、除了开展了“由偏振标记，由光纤远程柔性、共路传输的二合一固体微片激光回馈干涉仪”，还试探性的开展了“微片激光回馈干涉仪远程补偿、高测速关键技术研究”作为这个结题项目的超额，也为今后研究做一定铺垫。.3、本研究为摆脱测量光直射被测目标的惯例，光纤铺在地上，从一个工作台到另一个工作台，从一个房间到另一个房间，仅在被测目标处光纤准直头才对准目标测量。这就是我们实现的“无障碍传输测量”，同时，为适应远程测量和狭小空间测量奠定了原理和实验基础。.4、因激光器内干涉只发生在同一激光器的出射光和回馈光之间，垂直偏振光和平行偏振光互不串扰；且垂直偏振光（带有目标位移的信息+光纤被外界扰动的信息）和平行偏振光（仅带有光纤被外界扰动信息）的相位相减，消除了光纤被外界扰动信息而得到的仅是目标位移。如无这种外差结构，大距离传输时，温度、弯曲、外压力等引入的的噪声掩盖被测位移系统失效。.5、建立了完整的实验系统，达到指标：稳频精度10（-7），纳米分辨率，20米光纤，测量位移重复性1μm。.6、发表SCI收率论文7篇，申情专利9项。

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