Research Of Fiber Optic Shape Sensing Technology Based On Optical Frequency Domain Reflectometry

Shape sensing,through long-term and real-time shape monitoring,is widely used in transportation,communication,energy,power,aerospace,border security and other fields,to provide security for the life and property of the country and people.Fiber Optic Shape Sensing(FOSS),which relies on the advantages of high spatial resolution and high accuracy,has gradually become a research hotspot in recent years.In particular,the shape sensing based on Optical Frequency Domain Reflectometry(OFDR)is playing an important role in medical treatment and variant aircraft applications.However,there are still many problems and challenges in the shape sensing technology based on OFDR.For example,due to the influence of environmental factors,the useful information in Rayleigh scattering signals is easily"submerged";the normal bending of the multi-core fiber can be confused with the ambient temperature and internal torsion,resulting in complex Rayleigh scattering spectrum,which makes the shape sensing results inaccurate.Aimed at the above problems,the following are carried out:1.A local spectrum matching algorithm is proposed.By moving the local spectrum window and using the average Euclidean distance as a new evaluation criterion,the signal-to-noise ratio,the spatial resolution and the strain resolution of OFDR are further improved,which can solve the multi-peak and fake-peak problems existed in the traditional global spectrum cross-correlation algorithm.The experimental results show that the algorithm has higher accuracy in finding the wavelength shift,which provides a theoretical support for the follow-up optical fiber shape sensing.2.A two-dimensional shape sensor is designed and the optical fiber two-dimensional shape sensing system is built to measure two-dimensional shapes.By exploring the shift of Rayleigh scattering spectrum of the optical fiber under strain of compression and stretch,the relative error of linear fitting of the calibration value of curvature coefficient within the range of bending curvature of 0?20m^-1 is 1.8%.Then combined with the algorithm of two-dimensional shape reconstruction,the spatial resolution of 0.95 cm is achieved.The obtained relative error of shape reconstruction is less than 1%in the shape sensing experiment of 1 meter long optical fiber and it is verified that the sensor is temperature insensitive.The construction of optical fiber two-dimensional shape sensing system and the research of two-dimensional shape sensing provide the device foundation for optical fiber three-dimensional shape sensing.3.The mathematical and physical model of fiber three-dimensional shape sensing based on Frenet-Serret framework is established.Based on the regular distribution of the core in the seven-core optical fiber,the maximum bending curvature of 50m^-1and the measurement of the deflection angle of 0?360 ° are finally realized by measuring the wavelength shift of different cores.Combined with the three-dimensional shape reconstruction algorithm,a variety of three-dimensional shapes are accurately reconstructed.It makes full use of the advantage of high integration of multi-core optical fiber in three-dimensional shape sensing.