Research On Sensing Technology Of Intrafiber Interferometer Based On Microstructure

In order to meet the rapid needs of biochemical/medical high-sensitivity detection,human health monitoring,automatic driving,etc.,micro-structured in-fiber interferometers with miniaturized and integrated features have become a hot research topic in the field of optical fiber sensing.In this paper,arc discharge technology is used to design and prepare taper and spherical micro-structured in-fiber interferometers,which are respectively applied to triple-parameter simultaneous measurement and flow velocity measurement research.The main contents are as follows:(1)Using the beam propagation method,the principle of multi-mode interference(Multimode interferometer,MMI)and light field distribution characteristics based on the self-image effect are theoretically studied;The Mach–Zehnder interferometer(Mach–Zehnder interferometer,MZI)principle of tapered multimode fiber is analyzed.The principle of temperature and refractive index(Refractive index,RI)sensing of the modal interferometer is studied,and the feasibility of simultaneous measurement of tripleparameter is theoretically analyzed.(2)In order to solve the cross-sensitivity problem,a bias-taper hybrid interferometer is proposed and prepared,which realized precise and efficient synthesis of MMI and MZI spectra.And temperature,RI and strain sensitive characteristics tests are carried out.Experimental results show that MMI has RI-free characteristics and has a linear wavelength-intensity response to temperature and strain;MZI exhibits stable wavelength response characteristics in terms of RI,temperature,and strain.Furthermore,using the method of joint wavelength and intensity demodulation,the triple-parameter simultaneous measurement with high discrimination is realized for the first time.(3)The bending force models of various coupling structures are constructed,and the high sensitivity characteristics of the Michelson interferometer with micro-sphere pendulum structure are verified by simulation.The preparation of the all-fiber target structure is completed,and the relationship between the discharge intensity and the spherical diameter and diameter consistency is explored.Comprehensive flow velocity testing and cross-talk characterization experiments are carried out.The experimental results show that the sensor achieves a high sensitivity of-1.22 nm(cm/s)and a high stability of 1.3% at a flow velocity of 0-11 cm/s,with a resolution of 0.016 cm/s.The corresponding temperature and RI cross-talk are 0.05(cm/s)/? and 24.02(cm/s)/RIU,respectively.