Study Of Brillouin Distributed Sensor Based On Side Hole Fiber

Stimulated Brillouin Scattering(SBS)as a kind of third-order nonlinear process has been widely noticed since it was found.In the past 20 years,the distributed optical fiber sensors based on Brillouin scattering have been developed rapidly because of its long distance,high spatial resolution and high measurement precision.The polarization-maintaining fiber can further improve the precision of the system.Side hole fibers(SHFs)are a multipurpose polarization-maintaining fiber which can be filled with gas and liquid.Therefore,Brillouin distributed optical fiber sensors based on side hole fibers are of great significance and value.This paper first explores the side hole fiber brillouin sensing properties.One hand we put forward using the single mode and the side hole fiber brillouin sensing system to measure the parameters mixed of temperature and strain.And on the other hand,we analyzes the methods to improve the system precision.Firstly,the Brillouin effect in fiber and its dependence on polarization are analyzed by simulation.The influence of temperature and strain on the optical signal is simulated in distributed Brillouin time domain sensing system.The relationship between the Brillouin gain signal and the polarization state is obtained to improve the Brillouin gain of the system.Secondly,the Brillouin distributed sensing system is used to detect the side hole fibers.The temperature-dependent and strain-dependent coefficients of the Brillouin frequency shift are 1.08 MHz/? and 0.89 MHz/ ??,respectively,and the Brillouin frequency shift is 5 MHz.Compared with other types of polarization maintaining fiber,it has lower temperature sensitivity,higher strain sensitivity and larger axial shift.Finally,the mixed temperature and strain parameters were measured by the single-mode and side hole fiber distributed Brillouin sensing system.The temperature and strain accuracy of measurement were 1? and 20 ??.The errors of sensing system are analyzed,and the temperature and strain parameters depend on the refractive index,Poisson's ratio,Young's modulus and density.The dual-core fibers are designed and the coupling effects in the two-core fiber are analyzed.The simulation results show that when the core distance is more than 40 um,the dual-core coupling can effectively avoid the coupling effect compared to the Brillouin effect.