Experimental Study Of Brillouin-based Optical Time-domain Reflection Technology

Brillouin optical time domain reflectometer is a distributed optical fiber sensing system that can simultaneously measure temperature and strain.Compared with traditional sensors,the Brillouin optical time domain reflectometer has the characteristics of large capacity,high sensitivity,strong stability,corrosion resistance,etc.And it can be applied to large infrastructure such as tunnels,bridges,roads,dams,power,water conservancy.It has very strong practical engineering significance.Secondly,for natural disasters such as landslides and geology,effective health monitoring and timely early warning can be performed,which can protect people's property and life safety.Finally,the Brillouin optical time domain reflectometer has the characteristics of single-ended input,fully distributed measurement,and long sensing distance,which makes it a research hotspot for domestic and foreign researchers.First of all,this article introduces the background significance of this research and the current research status at home and abroad.The key principles and technical difficulties involved in the Brillouin optical time domain reflectometer are described.And they are the basic mechanism of Brillouin scattered light,the linear relationship between Brillouin frequency shift,intensity and temperature,strain,and Lorentz Shaped Brillouin scattering spectrum.Secondly,the experiment builds an experimental scheme based on the principle of using Brillouin scattered light.The scheme focuses on the performance parameters of the relevant important components involved in the optical path part and the circuit part of the experimental system,as well as the coherent reception of the Brillouin scattering signal and the microwave down-conversion scheme of the experimental system.And finally obtains the experimental results that meet the theoretical expectations.Finally,the Brillouin scattering signal obtained by coherent reception is processed.The first step is to denoise the signal,including the averaging method to remove noise and the Morlet wavelet analysis to remove noise.The second part is to use the Hilbert wavelet to de-envelop the de-noised signal.And it can obtain the Lorentz-shaped Brillouin scattering spectrum by sweeping the frequency.The final step is to perform Lorentz fitting on the obtained Brillouin scattering spectrum.The method involved is particle swarm optimization.The Brillouin frequency corresponding to the peak power of the Brillouin scattering spectrum can be obtained at about 10.84 GHz.