论文部分内容阅读
对保偏光纤应力传感器中应力方向对于拍长、双折射主轴、串音以及偏振态演化等特性进行了理论分析。从光弹效应和弹性力学理论出发,推导出同时存在几何双折射、内应力以及外应力情况下的折射率分布,并采用等效阶跃光纤近似法,理论分析和数值仿真了横向应力的方向对于保偏光纤拍长、偏振主轴方向、偏振耦合强度(串音)以及输出偏振态演化的影响。仿真结果表明:1外应力的大小和方向对保偏光纤的拍长都将产生影响,在靠近慢轴上施加压力会减少双折射,增大拍长;靠近快轴上施加压力会增大双折射,减小拍长。2外应力方向与快慢轴不重合时,随着应力的逐步增大,保偏光纤新的双折射轴逐步向外应力方向靠近。3输出偏振态在邦加球上的演化轨迹类似于长短轴逐步增大的椭圆,其周期与应力方向直接相关。利用这一现象,可以通过测量输出偏振态的演化轨迹同时测量出外应力的大小和方向。
The polarization direction of the polarization maintaining fiber optic stress sensor is analyzed theoretically with respect to the characteristics of beat length, birefringence principal axis, crosstalk and polarization evolution. Based on the theory of photoelasticity and elasticity, the refractive index distribution under the condition of geometrical birefringence, internal stress and external stress is deduced. By the equivalent step fiber approximation method, the direction of transverse stress is theoretically analyzed and numerically simulated For the polarization maintaining fiber length, polarization axis direction, polarization coupling strength (crosstalk) and the output polarization state evolution. The simulation results show that: 1 the size and direction of external stress will affect the beat length of the polarization-maintaining fiber, the pressure near the slow axis will reduce the birefringence and increase the beat length; the pressure near the fast axis will increase double Refraction, reduce the beat length. 2 When the direction of external stress does not coincide with the fast axis and slow axis, the new birefringence axis of PM fiber gradually approaches the direction of external stress with the gradual increase of stress. 3 The output polarization state is similar to the elliptical ellipse with increasing long axis and short axis. The period of the output polarization state is directly related to the stress direction. Using this phenomenon, the magnitude and direction of the external stress can be measured simultaneously by measuring the evolution trajectory of the output polarization state.