Designing And Performance Study Of High Sensitivity Fiber-optic Seismometer

Fiber-optic flexural disk seismometer is a new kind of vibration sensor,which has advantages,like higher sensitivity,lighter weight,immunity to electromagnetic interference,over traditional vibration sensors.All of these advantages make fiber-optic flexural disk seismometer well-suited to vibration measurement in many fields such as vehicles,navigation system in aerospace equipment,machinery,well logging and so on.Multiturn fiber coil-based(MTFC)fiber-optic flexural disk seismometer(FODS)has been widely studied for it could got higher sensitivity and directionality.MTFC based FODS have been studied during past years,but there are several problems,like can not estimate the performance before fabrication,which wates materials and time.Because of the randomness of fabrication without any guidance.This paper poroves that the performance of MTFC based FODS can be designed beforing fabrication via finite element method(FEM)and theoretical analysis by confirm the parameters.The main is contants as follow:Firstly,we obtained theoretical expressions of sensitivity and frequency in this paper and we taken the effect of MTFC into consideration.It is easy to find that the way of influencing the sensitivity and frequency of each parameters,like the thickness of flexural disk,the number of turns of MTFC,the thickness of epoxy glue and weight of inertial mass.We can achieve the desired performance of MTFC based FODS by combination of these parameters.Secondly,we built its model via finite element method analysis and analyzed how these parameters effect the sensitivity and frequency of MTFC based FODS,in order to solve the deviation between the practical FODS and theoretical values and affirm the ideal performance of MTFC based FODS.Thirdly,we studied the process of fabrication to ensure the parameter of FODS accords with the designed,like the features of the optical devices,geometry,the material parameters and inertial mass.Fourth,we fabricated sample FODSs according the parameters of FEM based model and tested their performance.At the beginning,we tested the strain distribution of MTFC and compared with simulated result.The tested result shows that they have the same characteristic and similar amplitude.Moreover,we tested the frequency and sensitivity of sample sensor and the error of sample FODS and its simulated model is less than 20%.Sample FODS is sited at the national seismostation and the sample measured the earthquake in Jiuzhaigou Valley.The research and the analysis of fiber-optic flexural disk seismometer that done in this papers can not only optimize the performance of seismometers that have been applied to actual measurements,but also provide theoretical design parameters for seismometers to be produced.