Research On Temperature And Refractive Index Sensing Technology Based On Three Core Optical Fibers

Fiber optic multi parameter sensors exhibit more obvious advantages than traditional electrical sensors in various practical scenarios due to their small size,high sensitivity,stable performance,simple structure,and strong resistance to electromagnetic interference.In recent years,a type of multi-core optical fiber has emerged that breaks through the maximum transmission flux of traditional optical fibers.Its mode to mode interference coupling presents a sine wave that can correspond to the measured wavelength drift and intensity change,achieving the purpose of detecting the measured,thus having great development space in the sensing field.This paper designs a novel microstructure fiber structure based on three core optical fibers to achieve temperature and refractive index detection.The specific work is as follows:Firstly,a sensing unit for Mach Zender interference of tapered fiber multimode fiber D type three core fiber multimode fiber was designed.Based on the FD-BPM algorithm,numerical simulations were conducted on the sensing unit,and the optimal conical length and length of the flat region were obtained;Secondly,in order to verify the temperature and refractive index sensing characteristics of the structure,numerical simulations were conducted on the sensing unit filled with PDMS in the D-type region using the FD-BPM algorithm.The effects of temperature and refractive index on the transmission interference spectrum were studied,and the temperature and refractive index sensing characteristics of the structure were explored,providing theoretical guidance for the preparation of subsequent sensing units and experiments;Finally,the Mach Zender interferometric sensing unit of conical fiber-multimode fiber-PDMS filled three core fiber-multimode fiber-single mode fiber was prepared.In order to suppress the thermal expansion effect of PDMS,improve its temperature sensitivity,and avoid cross sensitivity between refractive index and temperature,the temperature sensing unit is packaged and designed.At the same time,a temperature and refractive index sensing platform is built to conduct temperature and refractive index sensing tests on the sensing unit,and the experimental results are analyzed to optimize the sensing structure and improve the performance of the sensing unit.