Research On The Characteristics Of H-shaped Optical Fiber Refractive Index Sensor Based On SPR Effect

Optical fiber surface plasmon resonance(SPR)sensor has been widely applied in extreme environment monitoring,physical parameter determination,biomedical index testing,and food allergen screening due to its advantages such as anti-electromagnetic interference,corrosion resistance,small size,and good flexibility.This thesis proposes an H-shaped optical fiber refractive index sensor based on SPR technology in response to the practical engineering requirements of a micro high-sensitivity optical fiber refractive index sensor.A chemical method is employed to corrode a bow-tie polarization-maintaining fiber with a cladding diameter of 80 μm to obtain a fiber structure with stress zones completely removed.By coating the surface of the corrosion groove with a metal film,a optical fiber sensor is obtained for studying its refractive index sensing characteristics.The following theoretical analysis and experimental research are carried out according to the actual process requirements of the tests.Firstly,based on a thorough investigation of the domestic and international development status of optical fiber SPR refractive index sensors,research is conducted on a novel structured SPR refractive index sensor.A research scheme for an H-shaped SPR refractive index sensor based on bow-tie optical fiber is proposed,and its feasibility is demonstrated.Secondly,the basic principle of SPR is elaborately expounded.Through investigating the transmission mechanism of light,the generation principle and excitation mode of SPR,the sensing principle of H-shaped optical fiber is derived,which provides theoretical support for designing H-shaped fiber optic refractive index sensor based on the SPR effect.Then,according to the ultimate fiber structure obtained through chemical corrosion,simulation studies of the corroded region’s fiber end face are carried out using software to analyze the impact of different metal film types and thicknesses on sensor performance.After determining the optimal parameters for the sensing structure,research is conducted on the refractive index sensing characteristics of the sensor and the feasibility of measuring liquid refractive index using this sensing structure is verified through simulations.Finally,a fiber sensing structure is fabricated by coating a metal film on the groove surface of the corroded fiber to excite the SPR effect.An experimental setup is constructed to investigate the refractive index characteristics of the prepared sensor.The experimental results are scientifically analyzed,and the causes of errors are discussed,as well as compared with SPR-based sensors of different structures.The refractive index sensor prepared in this thesis can measure in real-time.Within the range of solution refractive indices of 1.3331 to 1.3725,the refractive index sensitivity reaches 2877.02 nm/RIU.This sensor has the advantages of a simple structure,convenient production,easy operation,and high sensitivity,making it a new type of refractive index sensor that provides a novel approach for the development of refractive index sensors.