Study On Micro-structure Sensing Characteristics Based On Fiber Micro-spheres And Tapered Fiber

In the current era of informationization and intelligence,information transmission,perception,and extraction are indispensable links,and sensing technology provides strong support for the normal operation of these links.Novel optical fiber sensing technology that uses light waves as a signal carrier,optical fibers as the transmission medium of light waves,and the detection of changes in external parameters is important in the fields of biological,medical,military,coal mines,petroleum pipelines,intelligent structures,and health inspection of large building structures Applications.This paper develops a new,low-cost,easy-to-manufacture,high-performance optical fiber sensor based on the coupling characteristics of fiber microspheres,the characteristics of light splitting and combining,and the strong evanescent field characteristics of tapered fibers.The main work of this article is as follows:1.Introduce the background,classification and application of fiber optic sensors.Summarize the latest progress of optical fiber sensors in detecting micro-displacement,temperature,refractive index,liquid level and other parameters,and analyze their advantages and current deficiencies.The basic theory of the fiber optic sensor is deduced,which provides a reasonable theoretical explanation for the working principle of the new fiber optic sensor designed in this paper.2.A micro-displacement sensor based on single-mode fiber(SMF)end-face microsphere coupling is designed.The fabrication method of optical fiber microspheres was described and the high coupling characteristics of optical fiber microspheres were experimentally confirmed.The microsphere on the end face of theoptical fiber is equivalent to a lens,which has a certain convergence effect on light,which improves the coupling efficiency of the optical fiber and increases the measurement range.The experimental results show that the sensitivity of the sensor is0.00401 dBm/?m in the displacement variation range of 0 ?m-3725 ?m at room temperature.3.A high-sensitivity temperature sensor based on Photosensitive Fiber(PF)is designed.The single-mode optical fiber microspheres and the photosensitive optical fiber microspheres are manually discharged to fuse into a peanut-type structure,so that they act as optical fiber beam splitters and combiners in an interferometer.Because the core of the photosensitive fiber is doped with boron and germanium,the thermo-optic coefficient and thermal expansion coefficient of the fiber core are increased,which is more sensitive to external temperature and has a high degree of integration.Experimental results show that: within the temperature range of 44 ?-64 ?,the sensitivity of the sensor is-386.96 pm/?,and the linear fitting degree reaches 99.76%.4.Designed a sensor based on distilled water to cover the coupling area of the ring fiber coupler to detect temperature.A single-mode optical fiber is double-folded and fused and tapered to form a ring-shaped optical fiber coupler.Two adjacent optical fibers interfere in the coupling region,and the temperature is sensed in combination with the thermo-optic effect of distilled water.The effects of different taper lengths on the interference spectrum were investigated experimentally.The experimental results show that the maximum sensitivity of the sensor is 151.35 pm/?in the temperature range of 35 ?-60 ?,and the linear fitting degree is 99.99%.In addition,this research group proposes a low-cost demodulation scheme.At a single wavelength,the sensitivity of the sensor is 0.311 dBm/ ?,and the linearity is99.825%.5.A single-mode optical fiber-tapered photonic crystal fiber(TPCF)-single-mode fiber(SMF-TPCF-SMF)structure liquid level index dual parameter sensor is designed.The temperature insensitivity of photonic crystal fiber is used to solve the crosstalk caused by temperature.In addition,experiments show that thecollapsed area of the photonic crystal fiber can be used as a beam splitter and combiner in an interferometer,and the obtained interference spectrum has a good extinction ratio.The effects of different taper lengths on the air holes and interference spectra of photonic crystal fibers were investigated experimentally,and theoretical explanations were made.The experimental results show that the maximum liquid level sensitivity of the sensor is 0.58466 nm/mm in the liquid level range of 0 mm-10mm(taking an aqueous solution as an example).In the refractive index range of1.336-1.382,the maximum refractive index sensitivity of the sensor is 195.969nm/RIU.In this paper,the microstructure sensing characteristics of optical fiber microspheres and tapered optical fibers are studied,and the detection of parameters such as micro-displacement,temperature,refractive index,and liquid level is used as an example to explore.If combined with new materials(graphene,magnetic fluid),more parameters can be developed,which has important research value and broad application prospects.