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基于光波导理论和传输矩阵法,研究光纤包层被完全腐蚀后的高斯变迹光纤布拉格光栅(FBG)在非均匀外部介质环境下的反射谱特性。仿真过程中,分别考虑高折射率区(1.43～1.45)和低折射率区(1.33～1.36)两种情况,同时假设该非均匀外部介质折射率(SRI)呈不同的线性函数分布。仿真结果表明,高斯变迹FBG的谱带宽、谱强度特性与SRI沿光栅轴向的线性分布梯度密切相关。随着SRI梯度增加,反射谱的3dB带宽也逐渐增加,此时高、低折射率区的梯度灵敏度分别为3.775×103 nm.mm/riu和3.72×103 nm.mm/riu。研究结果对高斯变迹FBG用于生化传感领域的非均匀介质测量具有一定意义。
Based on the optical waveguide theory and the transfer matrix method, the reflection spectra of Gaussian apodized fiber Bragg grating (FBG) under non-uniform external media are studied. In the process of simulation, two cases of high refractive index (1.43-1.45) and low refractive index (1.33-1.36) are considered respectively, and the refractive index (SRI) of the non-uniform external medium assumes different linear function distributions. The simulation results show that the spectral bandwidth and spectral intensity of Gaussian apodized FBG are closely related to the linear distribution gradient of SRI along the grating axis. As the SRI gradient increases, the 3dB bandwidth of the reflection spectrum gradually increases, and the gradient sensitivity of the high and low refractive index regions is 3.775 × 103 nm.mm/riu and 3.72 × 103 nm.mm/riu, respectively. The research results have certain significance to Gaussian apodized FBG for inhomogeneous media measurement in biochemical sensing field.