Study Of A Kind Of Simple Structure All Optical Fiber Interferometric Sensing Characteristics

The sensing structure of all fiber interference has been widely concerned since its emergence,because of its high sensitivity,simple fabrication process and compact structure.The existing optical fiber interferometric sensing structures generally adopt the mode field difference brought by the optical fiber natural structure.The core mode is coupled to the cladding mode,and the influence of the external parameters on the mode field in the cladding is realized.Besides,some sensing structures are made by special machining technology,which brings difficulties and cost burden to the fabrication of sensor structures.In this paper,a simple all fiber interferometric structure based on ordinary single mode fiber is proposed.The method of changing the structure of the weld joint through the fusion process is adopted,and the whole fiber interference structure is formed by the fusion of the core,and the sensing characteristics of the temperature,refractive index and stress of the structure are studied..The structure has the characteristics of low cost,simple process,good repeatability and high sensitivity.The main work of this paper is as follows:1.The current status of all fiber interferometric sensing structures is reviewed,including the development of the temperature,refractive index and stress sensing of all fiber interferometric sensors.2.The interference structure of the melting double ball optical fiber is proposed.The fabrication process of the sensing structure is introduced.The sensing process of the all fiber Mach-Zehnder(M-Z)interferometer based on the melting double ball structure is theoretically studied.And the distribution of the interference field of the double sphere M-Z sensing structure in the optical fiber is simulated by COMSOL software.The sensing formula of temperature,refractive index and stress of molten double sphere structure is derived theoretically.3.The experimental study of the temperature sensing characteristics of the molten double ball optical fiber interference structure.The experimental results show that interference spectrum is drifting to the long wave direction when the temperature increases from 35 C to 90 C,and the temperature-wavelength has a good linear relationship,and the temperature sensitivity is 73.1 pm/? at this wavelength.4.The experimental study of refractive index sensing properties of molten double ball optical fiber interference structure.The experimental results show that interference spectrum shifts to the direction of the short wave when the refractive index of the solution increases from 1.33 to 1.3765,and the refractive index-wavelength and the refractive index-light intensity both show a good linear relationship,and the sensitivity of the refractive index at the 1551nm interference valley is-33.984 nm/RIU and 50.164dB/RIU respectively.5.Theoretical analysis and experimental research on strain sensing characteristics of molten double ball optical fiber interference structure.The experimental results show that interference spectrum is drifting in the direction of short wave when the strain increases from 1057.2 to 10571.7.The strain-wavelength and the strain-light intensity at different interference wave valleys have a good linear relationship,and have the same sensitivity,the wavelength-strain sensitivity is 0.3pm/?? and the sensitivity of the light intensity-strain is 0.0018dB/??.6.Theoretical and Experimental Research on water pressure sensing characteristics of molten double ball optical fiber interference structure.The experimental results show that interference spectrum is drifting to the direction of short wave when the water pressure is increased from 98Pa to 588Pa,and the water pressure-wavelength shows a good linear relationship,and the sensitivity of water pressure is 500pm KP.