Research On Several Key Technologies Of Distributed Optical Fiber Sesening Based On OFDR

With the advent of 5G Internet of things,the Internet of things is gradually deepening in all aspects of daily life,and the demand for the interconnection of all things is increasing in various industries.As an important part of the technology perception layer of Internet of things,sensors have been widely studied and concerned.Optical frequency domain reflection(OFDR)is an important distributed optical fiber sensing technology.Due to its advantages of high spatial resolution,high signal-to-noise ratio and high sensitivity,optical frequency-domain reflection technology has attracted more and more attention in recent years,and has been widely used in aerospace,precision instruments,medicine,large buildings and other fields.At present,most of the researches on OFDR at home and abroad adopt the signal processing scheme based on computer software.Although this method is easy to test,it is difficult to meet the high-speed demand of OFDR technology because of the factors such as serial processing of software at computer side,which results in the OFDR sensing time generally at minute level.In this paper,the high-speed OFDR signal processing scheme is designed for the high-speed OFDR sensor.Based on the high-speed OFDR system built by FPGA development board in the laboratory,the experimental scheme of OFDR high speed and high spatial resolution strain sensing and two-dimensional real-time shape sensing is designed and verified,and the effectiveness of the high-speed OFDR signal processing scheme is verified.The main contents of the paper are as follows:1.According to the demand of OFDR high speed sensor,the relationship model between the parameters of tunable light source and the indexes of OFDR system is derived and obtained.The scheme of continuous frequency sweeping of high-speed OFDR system is designed,including the light source sweep parameters and working mode setting.The feasibility of the scheme is verified by experiments.2.A high-speed OFDR two-dimensional shape sensing scheme based on the strain curvature parameter mapping model and the recursive shape recovery algorithm is designed.The shape reconstruction process of the method is realized on MATLAB and LABVIEW processing platforms respectively.The experimental results show that the maximum deformation curvature of the object can be measured is 10 and the maximum sensing rate can reach 16Hz.The real-time shape change display is realized on the LABVIEW software interface,which verifies the feasibility of the two-dimensional shape sensing scheme.3.In view of the demand of OFDR system for high speed rate,high spatial resolution and long distance,high-speed real-time strain parameter sensor,high-resolution strain sensing of micro parts and long distance are designed.The experimental scheme of strain sensing is verified by experiments.The experimental results show that the whole sensing time of the system is not more than 50ms at the sensing distance of 5m,the high resolution sensing precision of micro parts can reach 5mm,and the longest sensing distance can reach 50m.The effectiveness of the design experimental scheme is verified.