Characteristic Analysis Of Distributed Optical Fiber Sensing Vibration Signal Based On FPGA

Acoustic sensing technology has important significance in the fields of seismic monitoring,structural health monitoring,pipeline leakage monitoring,and perimeter security.Fiber optic acoustic sensing technology is achieved by detecting changes in the refractive index and phase of the fiber caused by sound vibration.Distributed optical fiber sensing is mainly based on both scattering type and phase interference type.Scattered distributed sensing mainly includes distributed fiber sensing based on Rayleigh scattering,distributed fiber sensing based on Brillouin scattering,and distributed sensing based on Raman scattering;phase interference based There are mainly distributed optical fiber sensing of MZI(Mach Zehnder interferometer)and distributed optical fiber sensing based on Sagnac effect.Distributed optical fiber sensing based on Sagnac is based on the principle of equal optical path difference interference.The system uses broadband light source,which has the characteristics of low cost and high sensitivity.In this paper,the linear distributed optical fiber acoustic sensing technology based on Sagnac effect is studied,and the experimental system is built.The FPGA is used as the control unit for data acquisition and transmission processing.The system designs and verifies the Sagnac linear distributed transmission principle,FPGA and its control chip,and studies the passive homodyne demodulation technology based on 3×3 coupler.The verification results show that when the external sound frequency is in the range of 0-5 kHz,the sound signal can be better extracted,and the sound color and loudness of the sound can be judged according to the frequency.At the same time,data transmission processing through FPGA verifies that there are great advantages in data processing speed and system stability.The system can not only detect the vibration signal,but also restore the multi-point sound source through the demodulation principle,and obtain the specific tone,tone,loudness and other components of each sound,and remove the interference signal through signal processing.Determine the occurrence of an event.