Research On Decoupling Technology Of Brillouin-Raman Hybrid Sensor Signal

At present,distributed optical fiber sensing system is gradually gaining in favor of researchers with the advantage on the structure and properties,and the distributed fiber sensing system based on Brillouin scattering and Raman has the most rapidly development.However,the frequency and power of distributed Brillouin optical fiber sensing system are sensitive to temperature and strain at the same time,so it is difficult to achieve high precision measurement in the case of that the reference fiber is not used.If using reference optical fiber,requirements of laying optical fiber are highly demand.Therefore,the application of Brillouin fiber sensing is limited in some occasions where accurate measurement is needed.Although distributed optical fiber sensing based on Raman scattering can realize a high precision measurement of temperature,the measurement of strain can not be realized,so the application situation is very limited.According to the characteristics of Brillouin sensing system of temperature and strain,combining with long distance and high precision temperature characteristics of Raman sensing system,the method of Brillouin-Raman hybrid sensing,and researches the integration of sensing signal decoupling technology,realized the high precision measurement of temperature and strain.The main work of this paper is as follows:(1)For Brillouin distributed optical fiber sensing and Raman distributed optical fiber sensing technology principle analysis,mainly Brillouin distributed optical fiber sensing of temperature and strain and the relationship between the amount of frequency shift and power.The relation between the temperature and the Raman scattering intensity of Raman distributed optical fiber sensing,based on the analysis of the current situation and development of distributed optical fiber signal the sensing technique of Brillouin scattering and Raman scattering of the treatment methods and effects on the demodulation results,for decoupling subsequent Brillouin Raman fusion signal,lays the theoretical foundation for research progress,pointed out the direction.(2)The laser source of Brillouin sensing device and photoelectric converter of Raman sensing device was designed.According to the requirements of other key sensor module integrated sensing device in the selection is the main source for the selection of the photoelectric converter Brillouin scattering of high frequency and mature Raman sensing device.Based on the current Brillouin distributed optical fiber sensing system and Raman distributed optical fiber sensing system,a Brillouin Raman fusion sensing experimental device is constructed.(3)In order to understand the phenomenon of the temperature measurement value is smaller than the true value in Raman distributed optical fiber sensing demodulation technology,the investigation and experimental verification are carried out.According to the phenomenon of peak offset in the Stokes and Stokes signals mentioned in the literature,a method of peak shift demodulation is proposed to reduce the measurement error.Based on the measurement principle of Brillouin and Raman distributed optical fiber sensing,the strain demodulation formula of fusion sensing device is deduced,and the high precision measurement of temperature and strain is realized.(4)According to the fused sensing system,the peak shift demodulation method is verified experimentally.The signal of the fusion sensing is decoupled,and the integrated experiment of temperature and strain of the sensing system is designed.The experimental results show that the temperature demodulation in Raman distributed optical fiber sensor system,data acquisition card for the collected Raman backscattering in the Stokes and anti Stokes signal dislocation,method of peak shift after demodulation,can effectively reduce the measurement errors for strain sensor system demodulation fusion accuracy also has to improve significant effect.Finally,the experiment not only verifies the feasibility of Brillouin Raman fusion sensing system,but also realizes the high-precision measurement of the dual parameters of temperature and strain for single sensor fiber.