在光纤上采用激光微加工技术刻写周期性缺陷，形成FBG。当入射光进入FBG中，在满足布拉格条件的情况下，就会发生选择性反射，其余的波长透过光纤光栅继续传输，反射波长和光栅周期的关系如下：
The periodic defects are etched on the optical fiber by laser micro-processing technology, and FBG is formed. When incident light enters FBG, selective reflection will occur when Bragg condition is satisfied. The remaining wavelengths continue to transmit through FBG. The relationship between reflected wavelength and grating period is as follows:
其中，为光纤纤芯的折射率，为光栅的周期。
The refractive index of the fiber core is the period of the grating.
当光栅受到外部物理场(如应力应变、温度等)的作用时，反射光的波长也随之发生变化。根据发射光波长变化的大小就可以确定待测部位相应物理量的变化。
When the grating is subjected to external physical fields (such as stress, strain, temperature, etc.), the wavelength of reflected light changes accordingly. According to the change of the wavelength of the emitted light, the change of the corresponding physical quantity of the position to be measured can be determined.