Research On Shape Sensing Based On Multi-core Fiber And Distributed Strain Measurement

The fiber-optic sensing technology,which started in 1977,and has now entered the stage of equal emphasis on research and application.Nearly a hundred different types of optical fiber sensing technology have been developed.Optical fiber sensing technology has become an important indicator of a country's information technology.In recent years,fiber-optic sensing technology has been widely used in many research fields such as aerospace,oil and gas pipelines,fire monitoring,and bridge monitoring.Among them,distributed optical fiber sensing technology is one of the most important research directions in optical fiber sensing technology.Brillouin optical time domain analysis(BOTDA)has spatial resolution among various distributed optical fiber sensing technologies.The characteristics of high spatial resolution and long sensing distance are already a mature optical fiber sensing technology.At present,the main research direction is how to obtain more monitoring information through subsequent processing of the measured basic variables.This paper researches on fiber shape sensing based on multi-core fiber and distributed strain measurement,and converts the monitored strain information into shape information through related algorithms to achieve shape sensing.The specific research content is as follows:First,the basic theory of the Brillouin optical time domain analysis technology is described.And the differential pulse pair Brillouin optical time domain analysis(DPPBOTDA)with higher spatial resolution is introduced by introducing the limitations of traditional BOTDA technology.In this paper,the expression form of the parallel transport frame algorithm in the shape reduction is derived,and how the parallel transmission frame algorithm solves the shortcomings of traditional space curve theory is provided,which provides a theoretical basis for subsequent experiments.Then,a DPP-BOTDA system was built,and the spatial resolution is verified by the experiment,the specific parameters of the shape sensor structure of the multi-core optical fiber are measured and explained,and this data was used to provide basic experimental data for subsequent shape sensing experiments.The bending characteristics of the Brillouin frequency shift of the off-axis fiber core in the multicore optical fiber are verified.Finally,five kinds of measuring molds were designed and manufactured: three two-dimensional shapes and two three-dimensional shapes.The algorithm was written based on the parallel transport frame formula.The DPP-BOTDA system and shape reduction algorithm were used to collect data,process data,and demodulate shape information for each core of the multi-core fiber.And the causes of the errors are analyzed.The lowest error of the distal in the two-dimensional shape is 4.77%,and the lowest error of the distal in the three-dimensional shape is 7.25%.