Research On Shape Sensing Restoration Algorithm Based On Distributed Optical Fiber Sensing

Distributed optical fiber sensing technology has great application potential in intrusion monitoring,structural deformation monitoring,attitude monitoring,longdistance temperature monitoring and other scenarios due to its characteristics of antielectromagnetic interference,anti-corrosion,good security,flexibility and convenience.In recent years,with the efforts of domestic and foreign researchers,distributed optical fiber sensing has continuously improved in terms of sensing distance,sensing accuracy,resolution,and detection speed.At the same time,its application scenarios continue to increase,and shape sensing based on distributed optical fiber sensing has gradually become possible.Since the spatial reconstruction algorithm of shape sensing usually requires strain data with high spatial resolution,the current shape sensing based on distributed optical fiber sensing is usually used in short-distance and small-range scenes such as medical probes and catheter posture monitoring,spacecraft morphology monitoring,and robot joint monitoring.It is rarely used in long-distance large structures.This dissertation attempts to apply the idea of shape sensing to the long-distance optical fiber composite overhead ground wire(Optical Fiber Composite Overhead Ground Wire,OPGW)ice coating monitoringand one-dimensional shape sensing based on single-core fiber is realized in this scenario.In addition,this dissertation also explores the torsion problem in the three-dimensional shape sensing of the multi-core optical fiber.The specific research content is as follows:(1)In this dissertation,three core issues of shape sensing are used to analyze OPGW ice coating monitoring: sensor configuration,distributed strain measurement method and spatial reconstruction algorithm,and use it as the application of optical fiber shape sensing in one-dimensional sensing.Through the establishment of the mechanical model of the suspended cable,a method of reconstructing the strain distribution into the distribution of the thickness of the icing is designed.The method is verified by the simulation data of the cable tension and the experimental data of the suspended optical cable.The experimental results basically reflect the different ice thicknesses set in the experiment.Finally,the source of the error and the characteristics of the influence caused by the measurement error are analyzed.This project demonstrates the application prospects of shape sensing based on distributed optical fiber sensing in long-distance and large-scale scenes.(2)This dissertation points out the necessity of improving the demodulation method by observing the number of free variables in the demodulation equation of the curvature and torsion of the ordinary multi-core fiber.By establishing the model of strain,bending curvature and torsion angle,the demodulation method of bending and torsion at the same time is obtained when only one direction of torsion occurs.The effectiveness of this method is verified by simulation data.It has a certain significance to solve the torsion problem in optical fiber three-dimensional shape sensing.