Temperature-compensated balloon-like fiber magnetic field sensor with F-P structure based on PDMS

A highly sensitive balloon-like fiber interferometer based on magnetic fluid (MF) nanomaterial for magnetic field measurement is proposed in this paper. The Mach-Zehnder interferometer (MZI) was formed by bending the single-mode fiber (SMF) nested in Teflon tubes, and then MF was filled into the tube of the balloon-like fiber interferometer by using the capillary effect. When the external magnetic field intensity changes, the refractive index (RI) of MF changes, resulting in the change of the difference in optical path. The change of magnetic field intensity can be detected by the shift of interference spectrum. Besides, a Fabry-Perot interference (FPI) by filling the SMF with polydimethylsiloxane (PDMS), which is only sensitive to temperature, is proposed to compensate the temperature during sensing of magnetic field. The transmission signal of the MZI and the reflection signal of FPI are cascaded together to the circulator, optical switch and other components, so that the magnetic field intensity and temperature can be measured simultaneously. The temperature sensitivity of the MZI and the FPI is -0.919 nm/celcius and1.559 nm/celcius, respectively. FPI could be used to offset the effect of temperature. Consequently, the sensitivity of the magnetic field sensor can reach 0.683 nm/mT in the range of 0 to 10 mT, and the linear coefficient is 0.987. The system could be widely employed in lots of applications of magnetic field and tem-perature monitoring.