Research On Characterization Of Magnetic And Temperature Fiber Sensor Based On MZI

In recent year,optical fiber sensor has received extensive attention and research.However,the volume of existing sensors is mostly in the order of centimeters,which does not play the advantages of small size of the optical fiber.The miniaturization and sensitization methods of optical fiber sensors are studied in this paper.Based on the successful preparation of small size and high refractive index sensitivity tapered Mach-Zehnder interferometer(MZI),a high sensitivity magnetic field sensor and temperature sensor were prepared by taking full advantage of the magneto-optic effect and thermo-optic effect of EMG605 water-based magnetic fluid(MF)and Polydimethylsiloxane(PDMS).Firstly,a tapered MZI is fabricated by two multimode fibers(MMFs)and a tapered singlemode fiber(TSMF).The core diameter mismatch between MMF and single-mode fiber(SMF)makes the energy diffused into the cladding.while the TSMF can enhance the coupling ability of the fiber to excite higher-order cladding modes in a short distance and achieve the purpose of reducing the volume.In addition,the tapered structure enhances the evanescent field of the interferometer,making it more sensitive to changes in the external environment.In order to obtain the optimum parameters of multi-mode fiber and conical single-mode fiber for preparing interferometer,the simulation analysis is carried out.Finally,the simulation results are verified by experiments,the RI sensitivity of the sensor is 593.4 nm/RIU,and its length(2.32 mm)is1/10 of most of the same type of sensor.Secondly,the properties of two photosensitive materials(MF and PDMS)are introduced,and the magnetic field sensor and temperature sensor are prepared by coating the two materials on the interferometer respectively.The sensor characteristics of the two sensors were analyzed and verified by simulation and experiment respectively.The sensitivity of the experiment are-1.01 nm/m T and-0.53 nm/℃.The sensitivity of these two sensors is at a high level in the same type of sensors.Finally,the magnetic field sensors were placed in the magnetic field environment generated by the solenoid and the hoof magnet respectively to verify the sensing performance.The experimental results show that the magnetic field sensor is suitable for low voltage weak magnetic field measurement in the solenoid magnetic field environment.In the verification experiment of hoof-shaped magnet,the magnetic field distribution of the experiment is consistent with the simulation results.These two experiments prove that the magnetic field sensor has good sensing performance.Three kinds of sensors are proposed in this paper,among which the magnetic field sensor and temperature sensor are based on the tapered MZI coated with the MF and PDMS respectively.Compared with the same type of optical fiber sensor studied in the past,the three sensors have significantly improved the sensitivity and significantly reduced the size of the sensor.These two advantages make the sensor more widely used in the distributed measurement field in a small range.