论文部分内容阅读
基于模式耦合理论,采用基于光纤布拉格光栅(FBG)的二层圆光波导模型,通过转移矩阵法实现数值仿真得到升余弦变迹FBG在几种典型非均匀温度场下的反射谱。处于非均匀温度场下的FBG其纤芯、包层的有效折射率及光栅周期都会发生非均匀变化,因此其反射谱结构也会发生相应变化。仿真结果表明:非均匀温度场中升余弦变迹FBG反射谱与其温度梯度系数ΔTmax有很大关系,与均匀温度分布相比,其反射率明显下降,反射带宽明显展宽,反射峰出现分裂以至振荡;最大反射率随ΔTmax的增加呈非线性减小,其对应波长与温度梯度系数ΔTmax成正比,且不同的温度场对应不同的变化率,如线性温度场中其变化率约为0.004nm/℃,中心对称二次方分布温度场中变化率为0.006 5nm/℃。研究结果对于升余弦变迹FBG实现非均匀温度场的测量有重要意义。
Based on the model coupling theory, a two-layer circular optical waveguide model based on Fiber Bragg Grating (FBG) is used to obtain the reflection spectra of Raised Cosine Transform (FBG) under several typical inhomogeneous temperature fields by the transfer matrix method. In the non-uniform temperature field, the effective refractive index of the core and cladding of the FBG and the grating period all change nonuniformly, so the structure of the reflection spectrum of the FBG also changes accordingly. The simulation results show that the reflectivity of raised cosine apodized FBG in non-uniform temperature field has a great relationship with its temperature gradient coefficient ΔTmax. Compared with the uniform temperature distribution, the reflectivity decreases obviously, the reflection bandwidth broadens obviously and the reflection peak splits and oscillates . The maximum reflectance decreases nonlinearly with the increase of ΔTmax. The corresponding wavelength is proportional to the temperature gradient coefficient ΔTmax, and the different temperature fields correspond to different rates of change. For example, the linear temperature field has a rate of change of about 0.004nm / ℃ , The centrosymmetric quadratic distribution temperature field of the rate of change of 0.006 5nm / ℃. The research results are of great significance for the realization of non-uniform temperature field measurement of raised cosine apodized FBG.