The Experimental Study Of Brillouin Sensor Based On Micro-Fiber

Brillouin scattering is one of the most important nonlinear effects in the optical fiber,and it is an inelastic scattering phenomenon caused by light and acoustic interaction.Since the Brillouin frequency shift has a linear dependence on temperature and strain,it can be used for distributed sensors.Brillouin scattering based sensor has been applied for health monitoring of large building structures,submarine cable,submarine tunnels and so on.In the micro fiber,hybrid acoustic wave can be exited due to the small diameter of the fiber.Therefor the characteristics of Brillouin scattering might be different from those in conventional single mode fiber.The study of Brillouin scattering in micro-fiber is very important to expand the application of Brillouin sensors.In this thesis,we firstly study the principle of Brillouin scattering in the micro-fiber.And then,we observed the characteristic of Brillouin spectrum in difference micro-fiber produced by flame-brushing technique in the experiments.At last,we study the Brillouin sensing coefficient of temperature,strain and air pressure respectively,and compared those in conventional single mode fiber.From the experimental results,it is found that Brillouin scattering in micro-fibers is excited by the hybrid acoustic wave in the fiber,and its spectrum appears to be a multipeak structure.In the experiment,five Brillouin peaks is observed at 8 to 11 GHz.in the sensing experiment for temperature,strain and air pressure,the Brillouin scattering peak in the micro-fiber is more sensitive than those in the single-mode fiber.,And the efficient of temperature,strain and pressure for each peak are not the same thus it can be used to solve the cross sensitive problem of Brillouin scattering based sensing technique.