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强光致光纤布拉格光栅(FBG)光谱的变化是由非线性效应和光热效应共同作用的结果。基于FBG传感模型,利用非线性薛定谔方程和一维稳态热传导方程分析了非线性效应和光热效应各自对于光谱变化的贡献比例。通过分析波长漂移量与相位改变的关系,建立了基于FBG的非线性折射率系数计算模型;通过理论仿真光纤内温度分布情况,分析了光热效应对光谱啁啾化和波长漂移量的影响。理论与实验研究结果表明,对于普通单模光纤,当注入抽运光功率较小时,FBG光谱的变化主要是由光热效应造成的,而非线性效应则贡献较小。
The change in the spectra of a strong fiber-to-fiber Bragg grating (FBG) is the result of both a nonlinear effect and a photothermal effect. Based on the FBG sensing model, the contributions of the nonlinear and photothermal effects to the spectral changes were analyzed using the nonlinear Schrödinger equation and the one-dimensional steady-state heat conduction equation. By analyzing the relationship between wavelength shift and phase change, a nonlinear refractive index coefficient model based on FBG was established. The effect of light and thermal effects on the spectral chirp and wavelength drift was analyzed by theoretically simulating the temperature distribution in fiber. The theoretical and experimental results show that the change of FBG spectra is mainly caused by the photothermal effect, while the non-linear effect contributes little to the ordinary single-mode fiber when the pumping light power is small.