Fiber Optic Acoustic Signal Acquisition And Demodulation Technology Based On FPG

Compared with acoustic signal sensing technology using electrical means,fiberoptic acoustic sensing systems have the advantages of small size,corrosion resistance,electromagnetic interference resistance,and the ability to detect multiple physical parameters.Fiber-optic acoustic sensing systems are widely used in areas such as oil and gas pipeline intrusion monitoring,high-voltage transmission line health monitoring,railway engineering,and underwater attack and defense,and are gradually developing towards array and network formation.With the increase in the number of fiber-optic sensors in the system,the amount of data to be processed by the processor also continues to increase,and data processing speed has become one of the constraints on large-scale array reuse of fiber-optic acoustic signal sensing systems.To address these issues,the authors designed a fiber-optic acoustic signal real-time acquisition and demodulation system based on FPGA,which achieved the demodulation of phase information of fiberoptic acoustic signals.The specific research content is as follows:For the fiber-optic acoustic signal acquisition and demodulation system,the signal conditioning circuit for the data acquisition end is designed to achieve high-speed acquisition of photoelectric signals.At the same time,an automatic calibration program for the data clock and frame clock signals of the ADC chip was developed.The fiberoptic acoustic signal acquisition and demodulation system realized a FIR low-pass filter based on the BRAM cache.The FIR low-pass filter has the ability to load multiple acoustic signal-sensitive fiber sensing units and can be time-division multiplexed to multiple acoustic signal-sensitive units.The PGC demodulation algorithm based on the BRAM cache FIR low-pass filter architecture in the system can demodulate fiber-optic acoustic signal data of up to 256 acoustic signal-sensitive units.Using Xilinx’s xc7z035 series FPGA and ARM chip,a Fizeau-type fiber-optic acoustic signal acquisition and demodulation system based on FPGA was constructed and the PGC demodulation algorithm was verified.By analyzing the power spectral density of the demodulated data within the 150 Hz-1000 Hz sound signal range,the signal-to-noise ratio of the demodulated data is higher than 20 d B,and the real-time demodulation of the phase information of the fiber-optic acoustic signals is achieved,which reduces the data processing pressure on the upper computer.