Shape Sensing Based On Distributed Brillouin Optical Time Domain Analysis

After decades of development,optical fiber sensing technology have made great progress in the monitoring of environmental variables,such as temperature,vibration,strain and so on.Brillouin optical time domain analysis technology is a very mature optical fiber sensing technology.How to use the algorithm which can make the measured basic variables to get more complex monitoring variables to become another development direction of fiber optic sensing technology.Fiber shape sensing is a sensing technology which used measured strain data in fibers to reconstructed the shape of the monitored object through a special algorithm.Fiber shape sensing technology has great potential for applications in medical,aerospace,intelligent systems and structural health monitoring,and so on.In this thesis,we focus on the fiber shape sensing technology based on Brillouin optical time domain analysis.The details are as follows:(1)The relationship between pulse width and Brillouin scattering power spectrum in traditional optical time domain analysis technique has been expounded theoretically;the principle that the differential pulse improves the spatial resolution of the Brillouin optical time domain analysis technique is analyzed.We have deduced the Frenet-Serret formula which describes the characteristics of spatial curve.The bending curvature has been associated with the variation of Brillouin frequency shift,which provides a theoretical basis for the later experiments and algorithms.(2)We have built the Brillouin optical time domain analysis system.A twodimensional fiber shape sensor have been designed and manufactured.We have made a detailed experiment on the shape sensor.The relationship between the variation of Brillouin frequency shift and the bending curvature has been verified in experiment.We demonstrated that the two-dimensional shape sensor has a temperature insensitive characteristic.Finally,we have completed the data acquisition,shape reduction and error analysis of two-dimensional shape sensing.(3)We have completed the coupling experiment of single-mode fiber and multicore fiber,and the position coordinates of the core in multi-core fiber are determined successfully.The characteristic parameters of multi-core fiber shape has been demodulated,and the sources of error have been analyzed.