光子带隙光纤背向散射对光纤陀螺的影响机理及噪声抑制方法研究

Fiber optic gyroscope (FOG) is one of the most successful commercial fiber sensors and has been widely used as part of the inertial guidance and navigation system in both military and civilian applications. However, in some applications FOGs have to operate in an awful environment, such as the radiation or extreme temperature in space, the properties of fiber would change and then influence or even destroy the performance of FOGs. The advent of air-core photonic bandgap fiber (PBF) offers a radically new means to solve this problem. As light travels in air in PBFs, the sensitivity to temperature or electromagnet is much lower than that in traditional fibers, so PBF is thought to be an ideal choice for FOGs as it can improve the environmental adaptability as well as reduce the complexity, size, and cost of existing FOGs. Research about air-core photonic bandgap fiber optic gyroscope (PBFOG) has verified that some key properties of FOG are substantially improved by using an air-core fiber coil as the sensing coil, but there are still issues remained to be addressed before the PBFOG become widely used. One of the issues is about the increased noise caused by backscattering in PBF. As the backscattering in PBF coil is much stronger than that in conventional fiber, the mechanism of its influence on FOG is more complicated, and there is little investigation of this problem. As thus, a deep understanding of the mechanism of backscattering noise in PBFOG through comprehensive modeling and analysis is highly desired. In this programme, the backscattering in PBF coil and its relationship with structure and environment is modeled and analyzed through full vector finite element method, and the mechanism of its influence on FOG is studied. The backscattering noise in PBFOG is modeled and measured, and some noise suppression method is given. This programme points out the mechanism of backscattering noise in PBFOG, lying a solid theoretical foundation for improving the sensitivity of PBFOG. The design method of low-loss photonic bandgap fiber also shows great technological promise in the spread of PBF applications.

光子带隙光纤陀螺具有良好的环境适应性，是下一代光纤陀螺的发展方向。然而，光子带隙光纤的背向散射系数远高于普通石英光纤，由此引入到陀螺中的背向散射噪声比传统陀螺大很多，严重制约了光子带隙光纤陀螺的发展和应用。目前还尚无成熟的理论模型来描述光子带隙光纤背向散射对陀螺精度的影响，也没有通用的噪声抑制方法。本项目针对光子带隙光纤陀螺中的背向散射噪声开展研究，明确光子带隙光纤背向散射与光纤结构参数之间的定量关系，研究光子带隙光纤绕制成环后其背向散射受应力等因素影响的变化规律，揭示光子带隙光纤环中背向散射对陀螺噪声的作用机理，提出光子带隙光纤陀螺背向散射噪声的测量方法，并从光子带隙光纤结构设计和光纤陀螺光路设计两个层面提出背向散射噪声的抑制方法。本项目的研究将为提高光子带隙光纤陀螺的精度奠定重要的理论基础，形成的光纤结构设计方法也可推广到其它类型和结构的光子晶体光纤中，具有重要的工程应用价值。

光子带隙光纤陀螺具有良好的环境适应性，是下一代光纤陀螺的发展方向。然而，光子带隙光纤的背向散射系数远高于普通石英光纤，由此引入到陀螺中的背向散射噪声比传统陀螺大很多，严重制约了光子带隙光纤陀螺的发展和应用。目前还尚无成熟的理论模型来描述光子带隙光纤背向散射对陀螺精度的影响，也没有通用的噪声抑制方法。本项目针对光子带隙光纤陀螺中的背向散射噪声开展研究，基于偶极子理论建立了光子带隙光纤散射模型，明确了光子带隙光纤背向散射与光纤结构参数之间的定量关系，并提出了背向散射强度测试方法，实现了光子带隙光纤背向散射强度的精确测试，揭示光子带隙光纤环中背向散射对陀螺噪声的作用机理，提出光子带隙光纤陀螺背向散射噪声的测量方法，针对二阶背向散射噪声，依据光子带隙光纤与结构参数之间关系模型，提出了光子带隙光纤结构优化方案来进行抑制。本项目的研究将为提高光子带隙光纤陀螺的精度奠定重要的理论基础，形成的光纤结构设计方法也可推广到其它类型和结构的光子晶体光纤中，具有重要的工程应用价值。