Research On Preparation And Sensing Of Microporous Structure Optical Fiber Devices

The fiber-optic Fabry-Perot(F-P)sensor based on microporous structure has become one of the potential developing sensors since the characteristics of flexible and diverse structures in the field of fiber sensing.This paper mainly studies the microporous F-P sensor with integrated,miniaturized and multi-parameter measurement functions,and designs a composite F-P sensor structure with three reflective surfaces.Three tip-structured F-P sensors are fabricated by studying the technologies of micropore processing and fiber F-P cavity sensing technology.The response characteristics of the sensor to gas pressure and temperature,liquid temperature and refractive index are studied experimentally,and then the composite spectrums are separated using fast Fourier transform and Fourier bandpass filtering,so as to achieve the purpose of multi-parameter simultaneously distinguish measurement.The primary research contents and conclusions of this paper are as follows:(1)The laser processing system is optimized by studying the micromachining mechanism of 193 nm excimer laser.The laser imaging method is used to design the optical path of the regular microstructure pattern,and the microstructures with different regular shapes are processed on the silicon dioxide material,and the rectangular perforation technology of the processing rule is realized in the longitudinal direction of the fiber.Combined with the existing fiber-optic F-P sensor technology,the sensitivity characteristics of the composite F-P cavity sensor and the relationship between the cavity size and spectral effect of the F-P cavity are theoretically analyzed.In order to meet the need of sensing function,a sensor structure with a probe-type tip integrated composite F-P cavity is designed,and a theoretical model of the sensor transmission spectrum is established.(2)A kind of microporous fiber F-P sensor was fabricated by microporous processing technology of 193 nm excimer laser.The response sensitivities of the sensor are 0.010 nm/?,4.16 nm/Mpa,1020.5 nm/RIU and-0.181 nm/?,respectively in the gas temperature 25?-300?,gas pressure 0.1 MPa-0.7MPa,liquid refractive index 1.3352 RIU-1.3469 RIU and liquid temperature in the range of 30?-90?,which have been studied theoretical and experimental.The F-P cavity spectrum of the composite spectrum of the sensor is extracted using Fourier bandpass filtering,and then can be used to simultaneously distinguish between measured temperature and pressure.And the calculated average temperature and pressure errors are 0.67? and 0.017 MPa,respectively in the range of 25?-60? and 0.1 MPa-0.7 MPa.(3)A kind of UV glue modified microporous F-P sensor was fabricated by using a strong UV adhesive bonding technology.Results show that the sensor has multiple responses for the changes of same physical parameters.Four sensitivities are obtained in temperature measurement,0.748 nm/?,0.053 nm/?,0.014 nm/? and 0.011 nm/?,respectively.In addition,the sensor has high response sensitivity to pressure of the 8.45 nm/Mpa.The gas temperature and pressure sensitivity of the sensor is more than 66 times and twice than that of the microporous fiber F-P sensor,and the sensor is verified to distinguish measurement of temperature and pressure,and the relative errors both of temperature and pressure are 0.2% and 3.7%,respectively.The sensor has high response sensitivity of 156.8 nm/RIU to the refractive index in a liquid environment and the relative errors both of temperature and refractive index are 2.1% and 4.1%,respectively.(4)A kind of capillary microporous F-P sensor was fabricated by using the technologies of welding ang micro-hole processing.The sensor is made in view of the unevenness and non-smoothness of the microporous F-P sensor cavity wall.The F-P cavity wall smoothing and spectral regularization of the sensor can more accurately identify the signal during demodulation,thereby reducing the error caused by the irregular shape of the spectrum.The experimental results show that the sensitivity of the sensor is similar to that of the microporous F-P sensor.The sensitivity of the sensor to gas temperature,gas pressure,liquid refractive index and liquid temperature response is 0.010 nm/?,4.02 nm/Mpa,1132.9 nm/RIU and-0.190 nm/?,respectively.In summary,the microporous fiber F-P sensors which are fabricated by 193 nm excimer laser have advantages of compact structure,wide measurement range and high integration.The microaperture F-P sensor based on UV adhesive and the capillary are the further optimization of the microaperture fiber F-P sensor.The optimization not only solves the problems sensitivity and spectral smoothing of the microaperture F-P sensor,but also has advantages of stable working status,higher measurement accuracy,and more suitable for industrial measurement.