具有特征波长的少模光纤特性及传感应用

Characteristics and Sensing Applications of Few-Mode Fiber with Critical Wavelength

介绍了一种特殊设计的少模光纤及由少模光纤构成的单模光纤-少模光纤-单模光纤(SFS)传感结构。在对轴激发条件下,少模光纤芯子中仅有基模LP01和第一圆对称高阶模LP02传输,且SFS结构的传输光谱在工作波长范围内有一个特征波长。在特征波长附近相邻两个干涉峰间的波长间距达到最大,且在特征波长处干涉仪的输出光强不随波长变化,这使得特征波长在光谱中唯一且容易识别。理论和实验研究了SFS结构传输光谱的特征波长及其两边干涉条纹随轴向应变、温度、弯曲、液体折射率的传感特性,并将SFS结构用于轴向应变、温度、弯曲、位移、外界折射率和相对湿度的大范围、高灵敏度、多参量同时检测,为解决常规干涉仪存在的测量范围小、输出多值性等问题提供解决方案。

This paper reviews a specially designed ￡ew-mode fiber and a single mode fiber-few mode fiber-single mode fiber (SFS) sensing structure. Only the fundamental core mode LP01 and the first symmetric high order core mode LP02 are excited in the few-mode fiber under the axial to axial splicing condition, and there is a critical wavelength existing in the transmission spectrum of the SFS structure at the operational wavelength. Near the critical wavelength, the wavelength spacing between adjacent interference peaks reaches maximum, and the output intensity of the interferometer is fixed while the wavelength changes. Therefore, the critical wavelength is exclusive and easy to identify from the transmission spectrum. The sensing characteristics of the critical wavelength and the interference fringes in the transmission spectrum under strain, temperature, bending, and liquid refractive index are studied theoretically and experimentally, and the SFS sensor structure is applied to measure a wide range of sensing parameters including strain, temperature, curvature, displacement, surrounding refractive index, and relative humidity, with the advantages of large measurement ranges, high sensitivity, and multi-parameter measurement. Thus, the current problems of limited measurement range and multi-value outputs existing in the traditional interferometers can be solved.