A Technology Research Of Distributed Optical Fiber Sensing With Accurate Positioning

The distributed optical fiber sensing technology based on Brillouin scattering breaks through the traditional monitoring methods because of its distributed monitoring,ability to induct many parameters and resistance to electromagnetic,it can realize full range automatic monitoring and play an important role in large structures.In order to achieve full range distributed stain,temperature or fracture monitoring for large structures such as bridge,tunnel,subgrade,rail anchor and so on,it is necessary to set long distance(up to several kilometers or even a few tens of kilometers)optical fiber.The longer the optical fiber,the bigger the positioning error.This paper proposed a based-FBG(Fiber Bragg Grating)method to monitor the full range strain and identify damage precisely.The main researches are as follows:(1)On the basis of FBG and the stimulated Brillouin scattering sensing principle,we studied the coupling characteristics between them and researched interact with each other.We find that in the time domain SBS(Stimulated Brillouin Scattering)spectrum appear sharp peaks by using FBGs.This phenomenon lay the foundation for positioning accurately by using FBG.(2)This paper proposed the positioning principle based on FBG-distributed Brillouin optical fiber sensing technology,and test to verify it.The principle based on FBG and mutation position unchanged before and after the event.The experimental results show that,this positioning method is very effective and positioning error within10 cm.(3)When there is damage to the length of the structure within the spatial resolution of BOTDA(Brillouin Optical Time Domain Analysis)instrument,data fitting found that short range positioning rule of events.The positioning error is still 10 cm.(4)We verified the precise location method of using FBG-Brillouin distributed optical fiber sensing through setting up the simulation experiment for concrete beam localization.The results show that the method can realize positioning precisely and the error within 8 cm.