Research On Optical Fiber Deformation Sensing Technology

Deformation has become one of the key research contents of modern sensor measurement in civil engineering,mechanical equipment,aviation,medical equipment,and other fields.In these engineered systems,most structures deform due to their weight,temperature introduction,and external forces,which adversely affect the stability and service life of the system.Early eddy current,piezoelectric,acoustic emission sensors,etc.,are widely used in deformation monitoring.However,these sensors are susceptible to electromagnetic interference and make it difficult to detect system stability in harsh environments.Compared with these sensors,fiber-optic sensors have inherent advantages of light weight,immunity to electromagnetic interference,and corrosion resistance,which make them excellent candidates for deformation measurement in the fields above.Strain and curvature are two important parameters that reflect deformation.This paper focuses on the research on strain and curvature.The specific research contents are as follows:1.Aiming at the shortcomings that the strain sensing measurement method in shape sensing is usually based on wavelength demodulation,the sensitivity is limited by the spectrometer,and the cost is high,a new method based on Fiber Bragg Grating（FBG）combined with optical fiber is proposed.Fiber-optic strain sensor based on Fiber loop ring down（FLRD）technology.The experimental results show that when the applied strain ranges from 0 to 1250με,the experimentally measured strain sensitivity of the fiber Bragg grating FLRD device ranges from 5.82 ns/μεto 20.82ns/με.The strain resolution can reach 0.86με,and the best resolution is 0.24με.The accuracy is 2 orders of magnitude higher than the FBG strain sensitivity measured using a spectral analyzer.The system has the advantages of simple structure,reflection sensing,high measurement accuracy,and a large measurement range.2.Aiming at the disadvantages of the cumbersome manufacturing process and high cost of existing curvature sensors,a reflective tapered flexible curvature sensor based on fiber grating is proposed,which implants a single-mode tapered fiber into polydimethylsiloxane.（PDMS）composite as the sensing area to measure the curvature.The experimental results show that the film-like PDMS has good flexibility,the tapered fiber and the PDMS film can be bent synchronously,and the bending sensitivity is about 0.87688dB/m^-1～0.91757dB/m^-1.The sensor is flexible enough,simple to manufacture,and low cost to enable effective applications in certain life scenarios.3.The multi-point sensing application of a reflective tapered flexible curvature sensor based on fiber grating is proposed and realized.The experimental data show that the sensitivity of the sensing system does not change significantly compared with the single-point measurement during the multiplexing experiment of multi-point measurement.And when the multi-point measurement is performed,the sensors will not interfere with each other directly,and the stability of the sensors is also guaranteed to a certain extent.Since the sensor is simple to manufacture and the fiber grating multiplexing technology also has certain advantages,there is room for development in practical applications.The flexible curvature sensor is used for human activity monitoring.The experimental results show that the sensor can not only detect small muscle changes in the human body but also detect large movements.It has a good development prospect in the field of human activity monitoring.