Design And Performance Research Of Michelson Interferometric Sensor Based On Multi-core Fiber

With the rapid development of optical fiber sensing technology,new optical fiber sensors have been widely used in all aspects of industry,military and life,and have become an important member of the sensor field.Fiber optic sensors have the advantages of simple and compact structure,corrosion resistance,electromagnetic interference resistance and high sensitivity that other sensors cannot replace,so they have been extensively studied.At the same time,with the development of communication technology,ordinary single-mode optical fibers have been unable to meet the requirements for signal transmission capacity.However,the development and production of multi-core optical fibers have well met the requirements of communication technology for transmission capacity.In addition,the multi-core optical fiber has a special structure,and the corresponding structure and manufacturing method are processed in the process of developing the sensor,and a higher performance optical fiber sensor can be obtained.However,sensors made of multi-core optical fibers are not in-depth in research and application.Therefore,this paper studies sensors with multi-core optical fiber Michelson sensing structures of different structures.The main research work and content of this paper are as follows:(1)The development and application background of optical fiber sensors are discussed,and the working principles of interferometers with different structures are introduced in detail.(2)A Michelson liquid level sensor based on three-core fiber reflection structure is proposed.Experiments have proved that the length of the three-core fiber will affect the sensitivity of the sensor to measure the liquid level,and the increase of the sensing length will make the sensor sensitivity lower.The performance of the sensor when the three-core fiber is 3 cm is studied.When measuring with deionized water,the liquid level sensitivity is 392.83 pm/mm,and the linearity reaches 0.99946.The sensitivity of the sensor to changes in the liquid level will increase as the refractive index of the liquid increases,and the response of the liquid level sensitivity to the refractive index is4410.74351 pm/mm/RIU.The sensor performance is very stable in deionized water at20-90?,and the maximum temperature drift is 0.3001 nm.(3)A liquid refractive index sensor based on a single-mode fiber-no-core fiberfour-core fiber(SMF-NCF-FCF)Michelson probe structure is constructed.The simulation results show that light is excited in the NCF and couples into the core and cladding of the FCF at the junction of the NCF and FCF.The interference fringes are produced by the interference between the cladding mode of the FCF and the core mode of each core.The sensor's refractive index sensitivity and temperature sensitivity in different solutions were explored respectively.The sensitivity of the sensor in the refractive index solution prepared by Na Cl,sucrose and glycerol was 171.75346 d B/RIU,121.40514 d B/RIU and 207.49878 d B/RIU,respectively.The sensitivity of the sensor to temperature is 0.05 nm/?,and the influence of temperature intensity change on refractive index measurement is very small,almost negligible,so the problem of temperature cross-sensitivity is well avoided.(4)A Michelson interferometric sensor based on single-mode fiber-four-core fiberthin-core fiber(SMF-FCF-TCF)is proposed.Using an improved simple silver coating method,a reflective film is coated on the end face of the thin-core optical fiber to increase the light reflectivity.The sensitivity of the sensor's refractive index was tested.In the refractive index matching solution prepared by sodium chloride,the sensitivity was 137.317 nm/RIU.Through linear fitting,the linearity reached an excellent 0.999.The influence of temperature on the sensor was tested,and it was found that the influence of temperature change on the sensor was very weak,and it was not sensitive to temperature.(5)A dual-parameter sensor based on FBG cascaded single-mode fiber-photonic crystal fiber-seven-core fiber(SMF-PCF-SCF)reflective interference structure is proposed.Since the photonic crystal will form a collapsed layer during the fusion splicing process with other optical fibers,it can be used as a beam splitter and coupler for the sensing structure.In order to make the spectrum smoother and reduce the appearance of spurious peaks,a Faraday rotator(FRM)is connected to the end of the seven-core fiber.The FBG is cascaded with the sensor,and strain and temperature sensing tests are performed on it.The interference structure is sensitive to strain.The sensitivity of the sensor under a stress of 0-1000 ?? is-2.82 pm/??,and the linearity is0.995.In this case of cascade,FBG shows weak sensitivity to strain,and the sensitivity to temperature is 11 pm/?.