Fiber Shape Sensing Based On Distributed Strain Measurement

Optical fiber sensing technology is a new kind of technology which uses the light-wave as the carrier and fiber as medium to feel and transfer external measured signals.Recently,this technology has developed gradually in many domains.Brillouin optical time domain analysis(BOTDA)bases on stimulated Brillouin scattering that is caused by the interaction of the pulse light and the continuous light,realizing the distributed measurement and turning into the important contents.BOTDA has been widely applied to plenty of key fields because of its high spatial resolution and long transmission distance,such as in aerospace and national defense.This paper utilizes this technology to measure the distributed strain of sensing fiber and restores the bending shape according to the algorithm to accomplish the shape sensing experiment.The specific research contents are as follows:First of all,this paper states the principle of traditional BOTDA technology and how to use the differential pulse-width pair BOTDA to improve the spatial resolution,then infers the relationship between Brillouin frequency shift and curvature of fiber and the form of Frenet-Serret Equation when used to restore the shape.Then,we set up DPP-BOTDA system,design and make the shape sensors used in 2D and 3D experiments and finish related experiments,obtaining the measured data.In the 2D shape sensing experiment,this paper verifies the relationship between Brillouin frequency shift and curvature of fiber and collects the sensing data.In the 3D shape sensing experiment,we find all the core positions of the multi-core fiber,connect the multi-core fiber and single mode fiber under the condition of low loss and collect the sensing data.Finally,we infer the relationship between Brillouin frequency shift and curvature and torsion of the fiber.Based on Frenet-Serret Equation,we restore the built shapes in the condition of 2D and 3D and analyze the error.