Research On Broadband Vibration Sensor Based On Fiber Bragg Grating

Vibration phenomenon is very common in all kinds of production and living practices.With the deepening of understanding of vibration phenomenon and its application,people urgently need to carry out effective monitoring on all kinds of vibration.On the one hand,the vibration detection of large Bridges and all kinds of mechanical parts can monitor the structural health.On the other hand,in the field of oil exploration,the artificial introduction of seismic waves and detection can facilitate the oil positioning.All kinds of vibration sensors are effective tools for vibration monitoring.Electromagnetic interference is a common problem in traditional electric vibration sensors.Fiber-based vibration sensor has the natural advantage in this aspect.There are many kinds of optical fiber sensing technology for vibration monitoring,Fiber Bragg grating(FBG)technology is mature,but its application in vibration sensing is not enough.In this paper,the theory,structure,package and experiment of vibration sensor based on FBG are studied systematically,and finds that the position of the oscillator has a significant effect on the performance of the sensor.The main contents of this paper are as follows:(1)The temperature and strain sensing principles of FBG are theoretically analyzed and experimentally verified.The results show that the change of Bragg wavelength is linearly correlated with the change of external temperature and strain.(2)The sensing theory of vibration sensor based on FBG is analyzed and numerical simulation is carried out.The results show that the performance of the sensor is affected by the mass and position of the oscillator.The effect of additional spring on the performance of the sensor is also analyzed,the results show that its action is similar to that of increasing the mass of the oscillator.(3)A practical and cost-effective oscillator vibration sensor is presented.Seven vibration sensors with different parameters were fabricated by changing the mass and position of the oscillator.The sensitivity,frequency response range and transverse anti-interference ability were tested.The results show that the greater the value of the dimensionless parameter L₁/(L₁+L₂)of the oscillator position is,the greater the sensitivity of the sensor is,and the resonance frequency tends to decrease first and then increase,and reaches the minimum value when the oscillator is in the center of the sensor.When the total length is unchanged,the parameter L₁/(L₁+L₂)is increased from 0.5 to 0.75,the sensor sensitivity is increased by about10.3 pm/g,and the resonance frequency is increased by 60 Hz.This shows that the sensor sensitivity and the resonance frequency can be improved by changing the position of the oscillator.The change of the mass of the oscillator can only cause the opposite change of sensitivity and resonance frequency.