Research On High Spatial Resolution Distributed Optical Fiber Sensor Based OFDR

The distributed optical fiber sensor has arousen people's extensive initerest with the advantages of anti-electromagnetic interference,high pressure resistance,high precision when monitoring the environment changes.Optical frequency domain reflectometery(OFDR)which has the merits of high precision,high resolution and high sensitivity to reflection or changes of the link,are widely used in military and civilian fields.But the tuned laser used in the OFDR system has a problem of nonlinear frequency-swept,the performance of OFDR may be affected.In this paper,the nonlinearity of light source in OFDR system and the methods of phase compensation are studied.The deskew filter algorithm,match fourier transform algorithm and high-order phase noise compensation algorithm are mainly introduced.After the simulation of deskew filter algorithms and match fourier transform algorithm,high-order phase noise compensation algorithm is researched because of the estimation error of nonlinear phase in the other two algorithms.In the experiment,after the phase compensation using deskew filter algorithm,the spatial resolution of fiber end reflection at a distance of 4.2km is improved from 2m to 0.3m.The side lobe of the reflection peak can be eliminated effectively.In order to verify the match fourier transform algorithm,the length of the fiber under test is changed from 2km to 4.3km.The spatial resolution of reflection at a position of 4.3km is upgraded from 0.5m to 0.15 m after phase compensation.For the high-order phase noise compensation algorithm,the algorithm can not only improve the spatial resolution,but also can elevate the detection sensitivity.A reflection of AP C connector which is 120 m from the fiber end could be detected with spatial resolution of1.6m when the length of fiber is 4.3km.The results of experiment verified the effectiveness of the three compensation algorithms.