# Optical Fiber Current Sensors Based on FBG and Magnetotstrictive Composite Materials
## 4 Prospect of Optical Fiber Current Sensor Based on Magnetostrictive Composite Materials  
The improvement of sensor structure and magnetostrictive composite material not only reduces the production cost of the sensor, but also improves the performance of the sensor. The sensor structure is mainly studied from the shape of magnetostrictive material (magnetostrictive composite material), the shape of magnetic permeable material and the number of permanent magnets, etc. Among them, the shape of magnetostrictive material still needs improvement, such as how to make the material smaller and the magnetic flux density more concentrated. The improvement of magnetostrictive composites is mainly studied from the aspects of particle volume fraction, binder type, particle size, orientation magnetic field, and molding pressure. At present, scholars at home and abroad have not reached a consistent conclusion on the effects of particle size, volume content, orientation magnetic field, curing temperature, and molding pressure on the properties of magnetostrictive composites. Therefore, a large number of experiments are needed to unify the effects of particle size, volume content, orientation magnetic field, curing temperature, \begin{table}
\begin{tabular}{c c c} \hline \hline
**Serial** & **Influencing Factors of** & \\
**Number** & **Properties of Composite Materials** & \\ \hline
**10** & Forming pressure & 1. [PERSON] et al. and [PERSON] et al. think that the best molding pressure is 200 MPa \\
**10** & Forming pressure & 2. [PERSON] and others think that the best molding pressure is 150 MPa \\  & & 3. [PERSON] and others believe that the best molding pressure is 400 MPa \\ \hline
**11** & Doping rare-earth elements & GMPC doped with rare-earth elements is better than GMPC undoped with rare-earth elements \\ \hline
**12** & Magnetic heat treatment & GMPC after magnetic field heat treatment is better than GMPC without magnetic field heat treatment \\ [PERSON]hline
**13** & Particle size of magnetostrictive material & 1. [PERSON] et al. and [PERSON] et al. think that the best particle size range is \(>\) 200 μm \\  & & 2. [PERSON] et al. think that the best particle size range is 106–212 μm \\  & & 3. [PERSON] et al. think that the best particle size range is 50–80 μm \\  & & 4[PERSON] [PERSON] et al. think that the best particle size range is 212–300 μm \\
**13** & Particle size of magnetostrictive material & 5. [PERSON] and others think that the best particle size range is 450–900 μm \\  & & 6. [PERSON] others think that the best particle size range is 30–500 μm \\  & & 7. [PERSON] et al. think that the best particle size range is 100–150 μm \\  & & 8. [PERSON] and others believe that the best particle size range is 250–420 μm \\ \hline
**14** & Preparation technology & The composites treated by high-energy ultrasonic method are better than those treated by mechanical stirring method \\ \hline
**15** & Curing temperature & [PERSON] and others believe that the best curing temperature is 80 °C \\ \hline
**16** & Particle aspect ratio & [PERSON] and others believe that the best aspect ratio of particles is 10 \\ \hline
**17** & Powder crystal orientation & The properties of composites with different crystal orientations are different \\ \hline
**18** & Types of magnetostrictive materials & The properties of composites with different kinds of magnetic field stretching materials are different \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Cont. and molding pressure on the properties of composite materials. The next work is to use finite element simulation to guide the experiment. At the same time, the strain transfer efficiency and demodulation technology of fiber grating deserve further study. Conceptualization, S.X. and M.L. ; methodology, Q.P. ; validation, F.X. and H.X. ; investigation, C.L. ; data curation, B.L. ; writing--original draft preparation, Q.P. ; writing--review and editing, S.X. ; visualization, J.S. ; supervision, M.L. ; project administration, S.X. ; funding acquisition, F.X.