Research On All-fiber Fabry-Perot Interferometric Microcavity Senso

Because of its advantages of anti-electromagnetic interference,high flexibility,fast response and light weight,optical fiber interferometer has always had a place in the sensing field.In this paper,two different structures of optical fiber Fabry-Perot interferometers were designed and fabricated based on chemical etching method,and their theoretical analysis was carried out in detail.The experimental systems were built to test the refractive index and temperature.The main work of this paper is as follows:1.In order to solve the problem of temperature crosstalk of traditional optical fiber interferometers,a closed cavity optical fiber Fabry-Perot interferometer based on chemical etching is designed in this paper.Based on the theory of three beam interference,the effects of air cavity length and single-mode fiber cavity length on the reflection spectrum are analyzed.Fast Fourier transform was used to analyze its response to refractive index and temperature in frequency domain.The interferometer was fabricated by chemical etching and optical fiber fusion process.The amplitude demodulation method of fast Fourier transform was used to avoid the reading error caused by wavelength demodulation.The results show that the refractive index sensitivity is-6.751 a.u./RIU in the range from 1.333 to 1.398,and the interferometer is insensitive to temperature.2.In view of the complex fabrication process of optical fiber Fabry-Perot interferometer with open cavity,an optical fiber Fabry-Perot interferometer based on chemical etching and optical fiber fusion process is proposed in this paper.The electric field distribution of radial dislocation of multimode fiber and single-mode fiber was analyzed by using the finite-difference time-domain method.Based on the theory of double beam interference,the change of reflection spectrum under different open cavity length was analyzed.The change of reflection spectrum with refractive index of the interferometer was analyzed theoretically.The experimental results show that the refractive index sensitivity of the interferometer is1384.498 nm/RIU in the range from 1.333 to 1.364,and it has low temperature cross-sensitivity.3.A refractive index interferometer based on parallel-connected dual Fabry-Perot interferometers with Vernier effect is proposed.According to Vernier effect,the structure adopts open cavity Fabry-Perot interferometer and closed cavity Fabry-Perot interferometer in parallel.The theoretical simulation shows that the refractive index sensitivity is 6 times higher than that of a single optical fiber Fabry-Perot interferometer,which is between 1.33-1.35.The refractive index sensitivity of the parallel interferometer is as high as 6632.29 nm/RIU.The structure greatly improves the refractive index sensitivity.Under the condition that the sensing cavity length remains unchanged,the reference cavity length with magnification of 4and 5 is designed.The reference cavity sensors with different cavity lengths are connected in parallel with the sensing cavity sensor by using a coupler,and the magnification can be selected independently.