Study Of GMM Fiber Current Sensor Based On DFB Laser Sense Technology

The optical fiber current sensors have the advantages of high precision,anti-electromagnetic interference,which is suitable for online detection systems,and can satisfy the power grid demands of small,convenient and digitally.In this thesis,the distributed feedback fiber laser(DFB-FL)and giant magnetostrictive material(GMM)are combined to design a new DFB-GMM fiber optic current sensor based on the thories of the current sensor,GMM and fiber Bragg grating.The DFB-GMM current sensing mathematical model is constructed by studying the DFB-FL sensing principle and the magnetostrictive characteristics.According to the basic electromagnetic theory,the relationship between the measured current and the coil current is studied.By using simulation analysis method to calculate the effect of prestress change and permanent magnet geometry change on sensor sensitivity,the prestressing structure is optimized.The simulation results show that under the same voltage and with the prestress increases,the peak-to-peak strain first increases and then decreases.Furthermore,the waveform distortion decreases first and then increases.The application of moderately prestress and permanent magnets ensures the smallest waveform distortion.Simultaneously,these two applications also ensure the range and sensitivity of the GMM current sensor.By utilizing the prestress theory derived from simulation,the feasibility of the sensing probe structure is verified and the optimal prestressing range of the current sensor is determined to being approximately 6.5MPa.The DFB-GMM current sensing experimental system is complished,the results reveal that the range of the current sensor is 1～150A.The current sensor has the better accuracy and sensitivity measuring small current.