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利用全矢量耦合模方程提出并分析了一种基于纤芯存在光致双折射的长周期光纤光栅的环境折射率传感测量方法.以波长为谐振波长的完全偏振光为入射波,通过分析不同环境折射率下输出光的偏振态在邦加球上与参考点间球面距离的变化测量环境折射率.分析表明,在环境折射率1~1.30范围内包层半径为20.75μm的长周期光纤光栅传感器线性特性良好,灵敏度为0.356/RIU,可应用于湿度和气体的折射率测量;该分析方法适用于其他类型的双折射长周期光纤光栅传感器的设计.
A full-vector coupled-mode equation is proposed and analyzed to measure the environmental refractive index of long-period fiber gratings based on the presence of photindicator and birefringence. By using the fully polarized light with the wavelength as the resonant wavelength as the incident wave, The refractive index of the environment was measured by measuring the change of the polarization state of the output light at the ambient refractive index from the spherical surface to the reference point on the Bonga sphere.The analysis showed that the long period fiber grating sensor with the cladding radius of 20.75μm in the ambient refractive index range of 1 ~ 1.30 The linearity is good with a sensitivity of 0.356 / RIU, which can be applied to the measurement of the refractive index of humidity and gas. This method is suitable for the design of other types of birefringence long-period FBG sensors.