基于光纤陀螺的保偏光纤热致双折射

针对光纤陀螺在温度变化条件下的性能恶化问题,理论上分析了保偏光纤的热致双折射引起的偏振耦合是局限光纤陀螺精度的主要因素.采用有限元法计算光纤线圈在不同温度下的应力分布,并根据高低温不同的应力状态分别推导了双折射的变化情况.在光纤陀螺工作温度范围内,选取6个典型温度点计算光纤环上热应力和消光比的变化,结果显示,干扰双折射随温度变化的减小而减小,并将理论计算结果用测试消光比的试验验证.研究表明,双涂敷层光纤、胶粘剂、陀螺金属骨架材料的热力学性能的差异,导致光纤线圈在不同温度下折射率改变.在60℃时,光纤折射率差约为1×10^-4,与光纤本征折射率差5.5×10^-4达到同一个量级,这将严重影响光纤保偏性能及陀螺精度.

Thermally-induced birefringence of polarization optical fiber on gyro

To solve the performance labefaction problem of fiber-optic gyroscope (FOG) when its temperature changed, modes coupling caused by thermally-induced refractive index of highly birefringent optical fiber was analyzed to be the main reason of limitting the precision of gyro in theory. Finite element method was used to calculate stress distributing. Based on the stress state of high or low temperature, the variational instance of birefringence was conjectured respectively. Six typical temperature points were selected as work condition to calculate thermal stress. The result shows that thermal-induced birefringence variations reduces accordingly based on different temperature, tallying the experimentation well from the extinction ratio. The result indicates double-coated optical fiber loop changes its birefringence at temperature range , for the expanding coefficient of fiber dismatching that of the framework and glue. Thermally-induced birefringence is 1×10^-4 at 60℃, the same order with its own birefringence of 5.5×10^-4, and it deteriorates the polarization in optical fiber and decrease gyro precision furthermore.