High sensitivity optical fiber magnetic field sensor based on semi fixed extrinsic Fabry-Perot interferometer

A semi fixed extrinsic magnetic field sensor (MFS) with high sensitivity based on giant magnetostrictive material (GMM) and Fabry-Perot (F-P) was proposed here. The single-mode fiber (SMF) was only fixed at both ends of the GMM rod, and the connection between the SMF and quartz capillary was canceled, which significantly improved the conversion efficiency from the variation of GMM rod to the variation of cavity length. Consequently, the sensitivity of the MFS was greatly improved. Experiment results indicate that the sensor designed can produce good interference spectrum and is very sensitive to the change of magnetic field. Through measuring the magnetic field intensity, the MFS with high sensitivity of 1.867 nm/Gs to the magnetic field was obtained. The corresponding magnetic field resolution reaches 0.01 Gs, and the sensor has excellent linearity. In addition, the problem of temperature cross sensitivity was solved by series Fiber Bragg Grating (FBG). The sensor proposed is compact in structure and simple in fabrication.