Research On Optical Fiber F-P Transverse Pressure Sensor Based On Vernier Effect Sensitization

Transverse pressure monitoring is of great significance in the fields of structural health monitoring,medical diagnostic analysis,composite material performance evaluation.It has received extensive attention from researchers in recent years.Optical fiber sensors are widely used in transverse pressure monitoring due to their small size,high sensitivity and anti-electromagnetic interference.Currently,fiber Bragg grating(FBG)sensors are widely studied in the field of transverse pressure monitoring,but because they are sensitive to multiple parameters,the measurement results are easily affected by changes in environmental factors(such as temperature).Fiber-optic Fabry-Perot(F-P)sensors have gradually become a research hotspot in the field of transverse pressure monitoring due to their simple structure,high sensitivity,good stability,and low temperature cross-sensitivity.Based on previous work,this paper carried out the research of fiber optic F-P transverse pressure sensor based on bubble microcavity,and introduced a demodulation algorithm based on the Vernier effect to demodulate it,which effectively improved the sensitivity of the sensor.The specific research work is as follows :Firstly,MATLAB is used to simulate the Vernier effect theory,set various parameters,and find that the sliding cavity change is 1.17 nm.And because the parallel cavity spectrum is more complicated,it is not easy to be observed directly.We take the under envelope extreme point of the spectrum,data interpolation and curve fitting are performed on it,and the variation of the parallel cavity is 5.745 nm from the fitted spectrum,and the theoretical value of the Vernier magnification is 4.91.Secondly,an optical fiber F-P transverse pressure sensor based on an elliptical bubble microcavity is fabricated by using an optical fiber fusion splicer.Two different manufacturing techniques of SMF bubble microcavity preparation technology and Capillary elliptical bubble microcavity preparation technology are studied,and their preparation methods,manufacturing steps and interference spectrums are analyzed in detail,and the characteristics of the interference intensity of different microcavities is analyzed.The experimental analysis show that the two important factors that affect the sensitivity of the elliptical bubble microcavity are the cavity length and the wall thickness.The longer the cavity length,the thinner the wall thickness,the higher the sensitivity of the sensor,and it is more sensitive to external pressure.Thirdly,in order to improve the sensitivity of the elliptical bubble microcavity fiber optic F-P sensor,a double F-P interference sensing measurement system based on the Vernier effect is proposed to achieve sensitivity amplification.Two F-P sensors are connected in parallel through a 3d B coupler to realize the Vernier effect,which has the advantages of adjustable sensitivity and easy preparation.The experimental results show that the sensitivity of an independent elliptical F-P cavity is 1.32 nm/N,while the test sensitivity of a parallel elliptical F-P cavity based on Vernier effect demodulation is-6.41 nm/N,about 4.87 times of a single sensor,more in line with the theoretical value.Finally,a temperature experiment is carried out on the elliptical microcavity F-P transverse pressure sensor.The temperature sensitivity of a single sensor is 3.02 pm/?,and the temperature sensitivity of a parallel sensor is-11.05pm/?.The experiment results show that the sensor has extremely low temperature sensitivity.