Fabry-Perot Interferometric Fiber-optic Microcavity Pressure Sensor

As an important physical quantity,pressure occupies a very important position in scientific research.In this paper,two different optical fiber sensors including closed cavity and open cavity are designed and prepared,meanwhile,the measurement for pressure and temperature are carried out on them.The main contents are as follows:(1)The theory has studied the interference principle of a single F-P chamber structure.The demodulation method of the sensor is described in terms of intensity and phase demodulation.At the same time,the interference principle of the Vernier effect in parallel double-FP cavities is analyzed in detail.(2)The enclosed cavity fiber pressure sensor is designed by using polydimethylsiloxane(PDMS)as a rear end facial diaphragm of the F-P cavity.Since PDMS has high elastic,it is prone to deformation so that the gas pressure sensitivity is enhanced.The thickness of the PDMS diaphragm can be precisely controlled by improving the thin film manufacturing process,thereby enhancing the practicality of the structure.Through the finite element analysis method,the deformation of the PDMS diaphragm is analyzed,and the analysis results are consistent with the experimental results.Repeated tests were performed for measuring gas pressure to make sure that the sensor is of reliability and practicability.Experiments exhibit that the gas pressure sensitivity is up to 52.413nm/Mpa when the thickness of the PDMS is 3 ?m and the cross-sensitivity of the gas pressure over temperature is 0.00251Mpa/°C.(3)In order to improve the pressure sensitivity of the sensor,a parallel open-cavity fiber optic pressure sensor was designed and fabricated.The sensing cavity adopts the reflection surface formed by direct fusion of hollow core fibers(HCFs)with different inner diameters,and the reference cavity adopts the reflection surface of rigid material.The sensing cavity is fabricated by direct welding,which is simple and repeatable.The reference cavity is made of rigid materials to reduce the impact of the environment on it By connecting two F-P cavities in parallel to form an optical Vernier effect,the sensitivity of the sensor is further improved.Compared with the previously reported structure,the optical fiber pressure sensor proposed in this paper has the advantages of higher sensitivity,practicability and simplicity,and has very important significance of scientific research and practical value.