基于锥形单模光纤的MZI折射率传感器特性研究

Study on the Characteristics of MZI Refractive Index Sensor Based on Tapered Single-Mode Fiber

摘要: 本文提出并制备了一种基于锥形单模光纤(Single-Mode Fiber, SMF)与无芯光纤(No Core Fiber, NCF)级联结构的马赫–增德尔干涉仪(Mach-Zehnder Interferometer, MZI)折射率传感器。该传感器采用“SMF-NCF-Taper SMF-NCF-SMF”的级联结构，通过在SMF段引入锥区，利用锥形区域增强的倏逝场效应，提升了光场与外界介质的相互作用强度。基于光束传播法进行仿真分析，结果表明锥形结构可有效增强模式耦合效率。实验搭建了宽带光源与光谱仪组成的测试系统，在1.34~1.38折射率范围内对传感器性能进行了测试。结果表明，当锥区腰径为60 μm时，传感器的折射率灵敏度达174.4 nm/RIU，线性拟合系数R²为0.9964，具有良好的线性响应。该传感器具有结构紧凑、制备工艺简便、灵敏度高等优势，在生物医学检测、环境监测等领域具有良好的应用前景。

Abstract: This paper presents the design and fabrication a Mach-Zehnder Interferometer (MZI) refractive index sensor based on the cascaded structure of tapered single-mode fiber (SMF) and no-core fiber (NCF). The sensor adopts a cascaded structure of SMF-NCF-Taper SMF-NCF-SMF. By introducing a tapered region in the SMF segment, the enhanced evanescent field effect in the tapered area is utilized to improve the interaction strength between the optical field and the surrounding external medium. Simulation analysis based on the beam propagation method shows that the tapered structure can effectively enhance the mode coupling efficiency. A test system composed of a broadband light source and an optical spectrum analyzer is built experimentally, and the sensor performance is tested in the refractive index range of 1.34~1.38. The results demonstrate that when the waist diameter of the tapered region is 60 μm, the refractive index sensitivity of the sensor reaches 174.4 nm/RIU, with a linear fitting coefficient R² of 0.9964, indicating an excellent linear response. The sensor has the advantages of compact structure, simple fabrication process and high sensitivity, and presents promising application prospects in biomedical detection, environmental monitoring and other fields.