Pressure Sensor Technology Of Distributed Optical Fiber

In recent years,fiber optic sensor is developing quickly because of its outstanding advantages.It obtains the great attention of scholars both in China and worldwide.The optical fiber sensor has been widely applied to structural health monitoring and on-line monitoring fields.Although the China domestic study of optical fiber sensor is slower than abroad,but so far,research of fiber Bragg grating sensor in domestic has obtained relatively mature results.At the same time,distributed optical fiber based on Rayleigh Backscatter has received relatively sufficient research and application because of its high spatial resolution,however,there is little research in domestic.Dalian university of technology has gradually implemented research on that aspect.Distributed optical fiber sensor can measure strain and temperature directly.In order to verify the accuracy of strain measurement,measure strain on surface of triangle cantilever beam with optical fiber and strain gauge.The comparison results show that the deviation between distributed optical fiber and strain gauge is-16.842%~9.120%,which is in the allowable range of engineering application.It proves that the distributed optical fiber can be used to measure strain with high accuracy.To verify the accuracy of temperature measurement,distributed optical fiber and thermometer are used to measure water temperature changes.The comparison results show that the average deviation between distributed optical fiber and thermometer is-4.055%~10.157,which is also in the allowable range of engineering application.In order to study the multiple parameter measurement of distributed optical fiber,design an optical fiber pressure sensor structure based on circular flat diaphragm.If several pressure sensors are put together,pressure distributed monitoring can be realized in spatial scope.Finite element models(ABAQUS software)are used to analyze the deformation characteristics of pressure sensor.The results show that strain of the diaphragm is linear to the pressure.It is highly consistent with the theory based on small deflection assumptions.In order to calibrate the sensor,experiment device used for loading and unloading experiment has been designed.Experiment results show that the distributed optical fiber can measure strain of the diaphragm surface with high signal noise ratio(SNR),and thus reflect the strain distribution.The strain distribution is consistent with the trend of the numerical simulation results.Comparison results between loading and unloading experiment show that pressure sensor repeatability is good.Linear fitting correlation coefficient are all higher than 0.99.The pressure sensor has good linearity.The highest sensitivity of the pressure sensor is 10838.47??/MPa,when the radial strain of the diaphragm center is the output value.If tangential strain is used to the output value,the smaller radius is,the higher sensitivity is.The maximum resolution of pressure sensor can reach 92.268 Pa/??.