| Magnetic field sensors have attracted increasing interests due to its plenty of applications in navigation,vehicle,current detections,and information storage.In recent years,fiber magneto-optical sensors have received extensive attention because of their significant advantages of high detection sensitivity,low cost,small size,simple manufacturing process and the immunity to electromagnetic interference.Among various magnetic measurement approaches,optical fiber magnetic field sensors attached to magnetically sensitive materials have been recognized as a promising approach.However,thermal expansion exists in FBG and magnetostrictive material which may result in obvious measuring errors.Firstly,an in-depth research in this paper has been done on the temperature effect of the magnetic field,and puts forward the magnetic field sensor based on double grating is insensitive to temperature.Secondly,on the basis of the existing magnetic field sensor,the magnetic field method based on microwave photonics from light domain to electricity frequency domain,further improve the sensitivity.The main research content of this paper are as follows:(1)This paper briefly introduces the research status of magnetic field sensors at home and abroad,as well as the sensing mechanism of several typical magnetic field sensors,and classifies the magnetic field sensors proposed at present,and discusses the application fields and application prospects of magnetic field sensors based on different principles.(2)Aiming at the problem that the accuracy of magnetic field detection by grating and magnetostrictive materials is easily affected by temperature,a temperature-insensitive magnetic field sensor based on dual fiber Bragg grating structure is proposed in this paper,and experimental verification is carried out.In the sensor structure design,the existing Terfenol-D was modeled by COMSOL firstly,and the finite element simulation was carried out to simulate the transverse and longitudinal strain tension of Terfenol-D surface respectively,which verify the strain uniformity of Terfenol-D surface,and obtaining its magnetostrictive coefficient in all directions.The magnetostrictive coefficient is positive in the 0° to 53° direction and negative in the 53°to 90° direction.(3)The magnetic field sensor was tested in the static magnetic field with different magnetic field intensity and different temperature environment.The two central wavelengths of the two FBG are mainly determined by the magnetic field intensity and ambient temperature,as well as the thermal effect of the magnetostrictive material itself.In the same environment,the wavelength drift is linearly related to the magnetic field,not dependent on temperature.By monitoring the displacement of wavelength drift difference,the magnetic field measurement can be realized to be thermally insensitive to the magnetic field sensor.The dynamic range of the sensor was measured from 8 m T to 80 m T in the experiment.By uniformly increasing and decreasing the magnetic field intensity,the sensor exhibited good hysteresis and temperature insensitivity.And the dynamic response of the sensor is tested in the experiment,which has a low time delay,and the measured time of the actual data is 67 ?s.(4)In the last part,a high sensitivity and temperature-insensitive magnetic field measurement method based on a dual-ring OEO(Optoelectronic Oscillators)system is illustrated.The sensor in the scheme mentioned above is connected to the system,and two dispersive elements are added to the part connecting the sensor,so that the two gratings have different time delays.In this scheme,the equivalent fixed time delay based on dual frequency is provided by dual fiber grating,and the frequency signal of comb spectrum is obtained.Due to the cursor effect,this scheme has much higher sensitivity than measuring only one frequency information,and different magnetic field sensitivity can be obtained according to different FSR to meet the needs of different application scenarios. |
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