# Optical Fiber Current Sensors Based on FBG and Magnetotstrictive Composite Materials
## 3 Optical Fiber Current Sensor Based on Magnetostirctive Composite Materials
### Magnetstrictive Composites
For magnetostrictive composites with particle volume fraction of 20%, when the orientation magnetic field intensity is from 0 to 30 kA/m, the saturation magnetostriction of compos  
Figure 16: Optical fiber current sensor based on magnetostrictive composite material. Figure 17: Comparison of the relationship between magnetostriction and magnetic field strength of composites with different particle volume fractions when the particles are treated with coupling agent or not. ites increases with the increase of orientation magnetic field intensity; when the orientation magnetic field strength is greater than 30 kA/m, it is almost unchanged. Therefore, for the composite with 20% particle volume fraction, the best orientation magnetic field strength is 30 kA/m. Similarly, for composites with 30% and 50% particle volume fraction, the best orientation magnetic field strength is 80 kA/m and 100 kA/m, respectively. [PERSON] et al. [29] studied the effects of preloading stress and particle volume fraction on magnetostrictive composites. As shown in Figure 18, the author compares the relationship between magnetostriction and applied magnetic field of composites with different particle volume fractions when the pre-compression stress is 0 MPa and 10 MPa, respectively. As shown in the figure, when the pre-compression stress is the same, within a certain range of particle volume fraction, the larger the particle volume fraction, the greater the magnetostriction of the composite material. When the volume fraction of particles is 57%, the magnetostriction of the composites is maximum. At the same time, when the volume fraction of particles is the same, the magnetostriction of composites with pre-compression stress of 10 MPa is greater than that of composites with pre-compression stress of 0 MPa. [PERSON] et al. [30,31] studied the effects of TD particle size, particle volume fraction, and preloading stress on composites. Two kinds of samples with different particle size distribution, namely powder A with particle size of 38-106 \(\upmu\)m and powder B with particle size of 106-212 \(\upmu\)m, were manufactured by the author. It is found that when the pre-compression stress and particle volume fraction are the same, the magnetostriction of magnetostrictive composites is the largest when the particle size is 106-212 \(\upmu\)m. When the particle size and volume fraction are the same, the magnetostriction of magnetostrictive composites is the largest when the pre-compression stress is 2 MPa. At the same time, when the pre-compression stress and particle size are the same, the magnetostriction of magnetostrictive composites with 20% particle volume fraction is the largest. [PERSON] et al. [32] studied the effects of orientation magnetic field, particle size, and molding pressure on magnetostrictive composites. The author sifted the powder into three grades (below 50 \(\upmu\)m, 50-80 \(\upmu\)m, and 80-100 \(\upmu\)m). When the particle size is 50-80 \(\upmu\)m, the magnetostriction of magnetostrictive composites is the largest. It is found that when the applied magnetic field is higher than 3 kA/m, the magnetostriction of composites with orientation magnetic field. In this paper, Cold Isostatic Pressing (CIP) of 200 MPa was used to recompress the composite, and the density of the composite increased from 6.84 g/cm\({}^{3}\) to 7.24 g/cm\({}^{3}\). Figure 18: The relationship between magnetostriction and magnetic field strength of composites with different particle volume fractions. (**a**) The pre-compression stress is 0 MPa. (**b**) The pre-compression is 10 MPa. Under the same conditions, the magnetostriction of the composites after CIP treatment is obviously higher than that of the composites without CIP treatment. [PERSON] et al. [33] studied the effects of TD particle size, particle mass fraction, and molding pressure on magnetostrictive composites.