Research On Sensing Based On Micro-fiber Sensitization Technology

With the rapid development of contemporary information technology,optical fiber sensing technology is also developing continuously,which has attracted extensive attention in the fields of communication,aerospace,biological detection and so on.At the same time,the sensitization technology of optical fiber sensor is also put forward constantly to meet the needs of different occasions.Based on the characteristics of micro-nano fiber coupler,strong evanescent field after melting cone,photonic crystal fiber(PCF)and wet sensitivity of graphene,several high performance fiber sensors are proposed in this paper.The main work of this paper is as follows:1.The research background of optical fiber sensor sensitization technology and the classification of micro-nano optical fiber sensor are introduced in detail.The development status of micro-nano optical fiber couplers is discussed,and the sensing mechanism of micro/nano optical fiber couplers,photonic crystal fiber and graphene is introduced respectively,which lays the foundation for the follow-up work.2.A kind of micro-nano fiber optic strain sensor based on high sensitivity fusion cone coupling is proposed to realize high precision strain sensing measurement.After stripping off the coating layer of about 2 cm,the two single-mode fibers are wound together on the platform of optical fiber drawing system.Set the required pull cone parameters,turn on the hydrogen flow,The two optical fibers were pull-cone burned by hydrogen flame to prepare the optical fiber coupler,The strain measurement is realized by using the strong evanescent field characteristic after coupling.Through the repeated measurement of the sensor,it is concluded that it has good reversibility.In order to overcome the cross-sensitivity problem,the interference dip has different sensitive characteristics to temperature and strain,and the coefficient matrix is used to solve the influence of temperature on strain.The experimental results show that the strain sensitivity is 20.35 pm/?? and the corresponding linear correlation coefficient is 99.9%.7.All-optical fiber liquid level–refractive index–temperature(LRT)sensor was proposed on the basis of micro/nanofiber coupling ring(MFCR).Two twisted conventional communication optical fibers are tapered,merged,and refined in the preparation of MFCR.By detecting the sensing dips,the liquid level,refractive index and temperature can be measured respectively.The coupler will form two interference paths(odd and even modes)in x and y polarization states and the two slightly different lights superimpose to form the interference using strong evanescent field characteristics of fiber coupling in the process of gradual tapering.Results showed that maximum sensitivities of liquid level,refractive index,and temperature are 18.78 mmpm /,568.74 RIUnm / and 154.76 pm/?,respectively,in the optical fiber coupler with a width of 8 mm.3.In this paper,based on the theory,an experimental system of micro-displacement measurement is built to explore the response characteristics of different waist diameters to displacement.Experiments show that the micro-fiber coupler has high sensitivity to displacement.The display sensitivity of the micro-displacement sensor is 143.92 /mpm m,and the full-scale range is 195 mm.4.This study proposes a new type of fused cone Sagnac ring humidity sensor based on graphene properties.First,single-mode optical fiber(SMF)is fused with photonic crystal fiber(PCF)to form SMF–PCF–SMF interference.Then,the SMFs at both ends of the PCF are folded in half to form a ring.The ring is placed on the fiber pulling cone translation platform for pulling cone coupling.A Sagnac interferometer that connects the PCF is formed by applying the birefringence effect of melting cone coupling.The prepared interferometer is placed on a special optical platform,and graphene is coated on the fused cone area and the PCF.The excellent properties of graphene are utilized to measure humidity.Experimental results show that sensitivity to humidity is within the range of 36.0 %RH-75.3 %RH,reaching 340.13 pm/% RH.5.A novel birefringent fused-cone coupling Sagnac-interference refractive index sensor is proposed in this study.Using the strong evanescent field characteristics of fiber coupling and the birefringence effect in the coupling region,the prepared sensor is placed in a solution with different refractive index.Experimental results show that the sensitivity reaches 186.656 nm/RIU.in the refractive index range of 1.339-1.367.In this paper,the structural characteristics of micro-nano fiber coupler and fused cone Sagnac ring interference sensor are analyzed and studied,and the physical quantities such as strain,refractive index,temperature,liquid level,micro-displacement,humidity and so on are detected.The sensor structure proposed in this paper is simple to manufacture and low cost,which can be used for reference in other fields.