线性啁啾光纤光栅受到横向应力作用时会产生轴向展宽。当作用线度即光纤 光栅受力区域长度与光纤直径相当时,该展宽不能忽略。基于空间弹性力学受力分析,可得到其轴向展宽导致的相移。 该光栅光谱中产生的透射峰位置与该相移的大小和位置有关。同时,横向应力会导致双折射现象。综上所有因素,建立了 利用斯托克斯参量(Stokes parameters)实现小线度作用区域即点式横向应变传感的理论模型。计算与实验结果表明:线 性啁啾光纤光栅在点式横向应力条件下,应力大小在弹性限度范围内与Stokes-s1参量峰值呈线性变化关系。Stokes-s1参量谱 峰波长与横向应力作用位置相对应,且与应力大小有关。通过分析透射谱的Stokes-s1参量,可实现对横向应力大小和位置的传感。

There is some axial extension in the applying scale of linearly chirped fiber Bragg grating(LCFBG) with transverse strain, which should be considered when the length of the applying scale is the same order of magnitude as the diameter of fiber. Based on the analysis of spatial elasticity, phase shift in the modulated refractive index distribution of LCFBG resulting from the axial extension is obtained. And the transmission spectrum peak created in grating spectrum is related to the value and position of phase shift. Furthermore, transverse strain can lead to birefringence. Considering all the factors aforementioned, the theoretical sensing model of transverse strain in small applying scale that can be treated as a point is introduced, in which the Stokes parameter characteristics of LCFBG are very important and useful. Simulation and analysis results show that the transmission coefficient grows exponentially with transverse strain but the peak value of transmission Stokes parameter spectrum is linearly dependent on the value of transverse strain applying in LCFBG. There is a one-to-one correspondence between the peak wavelength of transmission Stokes-s1 parameter spectrum and the applying position of transverse strain. And the peak wavelength of transmission Stokes-s1 parameter spectrum grows linearly with the value of transverse strain. So the position and value of transverse strain in small applying scale can be converted through the analysis method of measuring the transmission Stokes-s1 parameter spectrum of LCFBG.