The Study Of Characteristics And Application Of Vector Sensing Base On Excessively Tilted Fiber Gratings

In the field of aerospace,geologic examination,mineral exploitation and power transmission,real-time and accurate detection and acquisition of vector field parameters such as seismic waves,gravity fields,and electromagnetic fields are of great significance for system security,environmental status assessment,and building health detection.Optical fiber vector sensors have been widely used in various fields mentioned above due to their small size,light weight,high sensitivity,and resistance to electromagnetic interference.However,most of the existing sensors have the disadvantages of complex manufacturing processes,bad repeatability,weak mechanical strength,and unstable sensor performance.Therefore,there is an urgent need to design new fiber-optic vector sensors with simple structures,high sensitivity,and strong applicability.In this paper,the configuration of using an excessively tilted fiber grating(ExTFG)as a vector sensor device is proposed together with theoretical analysis,experimental verification and sensing applications,which provides a new idea for vector sensing.The research contents are mainly as follows:(1)The coupling mode theory,phase matching conditions and sensing principles of ExTFG are theoretically analyzed.The relationship between the mode effective refractive index,grating period,mode order and resonance wavelength,and cladding mode field distribution of Ex-TFG are simulated.(2)Ex-TFG was fabricated by the amplitude mask method,and its spectral characteristics,temperature sensitivity,refractive index sensitivity,and mode near-field distribution were measured experimentally.And the characteristics of its directional sensitivity were investigated through the experiment of one-side immersion of the grating.The experimental results show that Ex-TFG has a higher refractive index response and a lower temperature cross sensitivity,and exhibits an orientation-dependent refractive index sensitivity.(3)The characteristics of magnetic fluid are introduced in detail,the vector magnetic field sensing mechanism is discussed,and a highly sensitive vector magnetic field sensor is made by combining magnetic fluid and Ex-TFG.According to the spectral interrogation results and the direction of fast/slow axis,the vector information of magnetic field can be measured.The experimental results show that such a magnetic field sensor can achieve the magnetic field intensity sensitivity of 2.45 nm/m T and the orientation sensitivity of 0.41 nm/deg.