保偏微结构光纤啁啾光栅折射率传感特性分析

将有限元法和传输矩阵法相结合，系统地研究了保偏微结构光纤(PM-MOF)啁啾布拉格光栅的折射率传感特性。仿真研究了光纤空气孔中充入不同折射率被测物时啁啾光栅的反射谱，结果表明随着被测物折射率的增加，反射谱的面积出现明显变化，由此得到了光栅反射谱面积与被测物折射率的关系。分析了中心孔直径、啁啾系数、切趾函数等光栅结构参数对反射谱的影响。分析表明由于光纤两个方向的偏振模对温度、噪声等干扰响应相似，因此利用两个偏振模式反射谱的相对变化进行监测能够有效地降低干扰，提高传感器的稳定性;其次，由于反射谱面积正比于光强，这一方法将光栅的光谱解调转化为光强解调，简化了解调系统，便于现场实时测量。研究结果为保偏微结构光纤光栅在折射率传感器及其生物传感器方面的应用提供了理论依据。

The Refractive Index Sensing Characteristics of Polarization Maintaining Microstructured Optical Fiber Chirped Grating

The refractive index sensing characteristics of the polarization maintaining (PM) microstructured optical fiber (MOF) chirped grating was systematically investigated based on finite element method (FEM) and transfer matrix method (TMM). The chirp Bragg grating reflection spectrum was numerically analyzed with the fiber air holes injected with different refractive index medium, and the relation between the reflection spectrum area and the analyte refractive index is discussed here. The analysis results show that when the analyte refractive index increases, the reflection spectrum area will be reduced; and the detection demodulation is simplified with the light intensity demodulation. Moreover, the dependence of the reflection spectrum on the center big holes size, the chirp coefficient and the site function was studied. Since two polarization modes respond similarly to the outside perturbation, the fiber possesses high stability. The results provide the theoretical basis for the application of PM-MOF grating in the optical fiber refractive index sensor and the optical fiber label-free biosensing.