Research On Three-dimensional Curve Reconstruction Based On Multicore Fiber And OFDR

Three-dimensional(3D)curve reconstruction is widely applied in various fields,such as aircraft structural health monitoring,precise control of robot arms,etc.It has become a trending research topic to accomplish the reconstruction by using optical fiber with specific structure and distributed strain sensing technology.This thesis focuses on leveraging multi-core fiber(MCF)and optical frequency domain reflectometry(OFDR)for the research.The main contents include:(1)The basic composition of the 3D curve reconstruction system based on MCF and OFDR is introduced,the main factors affecting the strain sensing performance of OFDR system are analyzed,and the mapping relationship between the axial strain and deformation of the MCF with straight cores is derived.The algorithm of 3D curve reconstruction based on the rotation minimizing frame is presented.(2)A 3D curve reconstruction method based on MCF with straight cores and OFDR is proposed.Furthermore,The impact of parameters on the reconstruction accuracy of typical curves such as straight line,arc,3D S-shaped curve and 3D equidistant helix are evaluated and organized.The parameters include but not limited to the core spacing of MCF,Rayleigh scattering coefficient,the spatial resolution of OFDR and different curve reconstruction algorithms.The simulation results show that when Rayleigh scattering coefficient is-60 d B/m,the core spacing of MCF is 80 μm,and the spatial resolution of OFDR is 5 mm,the curve reconstruction algorithm based on the rotation minimizing frame can be used to reconstruct the above curves.For the reconstruction of a 3D S-shaped curve with a length of 1 m,the root mean square error of reconstruction is 2.75 mm and the tip position error is 4.80 mm.Moreover,a spatial resolution optimization method based on all-phase FFT is proposed.The simulation results show that the spatial resolution of OFDR can be improved from 0.023 mm to 0.013 mm when the frequency sweep range of the laser is 60 nm.(3)A 3D curve reconstruction experimental system based on MCF and OFDR is set up,which is designed to evaluate the effects of the core spacing of MCF with straight cores,OFDR spatial resolution,and different curve reconstruction algorithms on the reconstruction accuracy of typical curves such as straight line,arc,2D S-shaped curve and 3D equidistant helix.The experimental results show that when the core spacing of MCF is 80 μm,OFDR spatial resolution is 5 mm,the curve reconstruction algorithm based on the rotation minimizing frame can be used to carry out the reconstruction of the above curves.For the reconstruction of a 2D S-shaped curve with a length of 30 cm,the root mean square error of reconstruction is3.09 mm,and the tip position error is 7.03 mm.The experimental results are basically consistent with the simulation.