Demodulation System Of FBG Acceleration Sensor Based On DFB Laser

Vibration signals have important significance in many areas,including the civil engineering,aviation and large machinery.Fiber Bragg grating sensors have the advantages of small size,light weight,and strong resistance to electromagnetic interference.They have been widely studied and used to monitor vibration signals.The fiber Bragg grating demodulation system is also a hot topic of research.At present,a variety of acceleration sensors have been developed at home and abroad,and the research on fiber grating demodulation systems has become more and more mature.However,the demodulation systems at home and abroad are mainly concentrated in the low frequency area,and there are still some shortcomings in the detection of high frequency signals.This paper focuses on data acquisition for fiber Bragg grating acceleration sensors.By using a combination of narrowband light source demodulation and intensity demodulation,a high-speed fiber grating acceleration sensor demodulation system based on distributed feedback lasers is built.The following work results have been obtained:(1)The fiber grating acceleration sensor was designed.By studying a lot of references about the fiber grating acceleration sensor at home and abroad,this paper explains the theoretical model of the fiber grating acceleration sensor in detail,design and manufacture a fiber Bragg grating accelerometer with equal strength cantilever structure.The accelerometer has been tested and calibrated.The calibration results show that the calculated value of natural frequency is significantly different from the actual frequency,which is 86 Hz.However,in the acceleration range of 0.5g ~ 2.5 g,the sensitivity of the acceleration sensor can reach 6.7 pm / g,the linearity can also reach 0.9955.At the same time,this paper developed a dual-diaphragm fiber grating acceleration sensor and completed the theoretical analysis and preliminary verification experiments.It was proved that a complete waveform can be obtained at a frequency of 50 Hz and an acceleration of 2.5 g.(2)For the fiber Bragg grating acceleration sensor,an intensity modulation type demodulation scheme based on the narrowband light source demodulation method is constructed.By analyzing several commonly used wavelength demodulation methods,the demodulation scheme proposed in this paper is feasible,and the demodulation method has high accuracy and fast demodulation speed,which is advantageous in practical engineering applications.By elaborating on the DFB laser,a light source module for the DFB laser is designed.The wavelength scanning range of the light module can reach 3.8nm,the external temperature of the light source can be controlled at about 30?,and the temperature floating value is ± 0.1?.(3)Built the entire fiber grating demodulation system,and a demo program for the PC is written using LabVIEW software.The demodulation program contains three main core functional modules.The data communication module is responsible for the data transmission between the PC and demodulator.The main function of temperature parameter setting is to calculate the temperature at the half-wave width of the optical power spectrum.The main function of the storage module is to store the monitored data.In addition,the functions owned by the LabVIEW software can be used to improve the software.The demodulation software runs well and can achieve all functions such as communication,display and storage.(4)After the acceleration sensor is completed,the sensor is connected to the entire demodulation system and going to the performance test.The acquisition frequency of the demodulator is 500 Hz,and the demodulation accuracy can reach 0.02 mV,which can demodulate a complete vibration signal.The signal is stable after adding a filter,which shows that the demodulation system can complete the demodulation of the FBG acceleration sensor.