A Novel Optical Fiber Magnetic Sensor Based on Electroforming Long-Period Fiber Grating

In this study, we present a novel optical fiber magnetic sensor based on electroforming long-period optical fiber grating (ELPFG) with a periodic polymer-metal (SU-8 photoresist and nickel) structure that is fabricated via a LIGA-like process. We measure the magnetic field through the nickel grating on the optical fiber, and an ELPFG magnetic sensor calibration experiment is also described. The coil produces a magnetic field to modulate the ELPFG, and we use an optical spectrum analyzer to analyze the resonant wavelength and changes in transmission loss. It is discovered from the experimental results that the optimal sensitivity of the ELPFG is -0.465 dB/mT, the linearity is 0.965, and the transmission loss will gradually increase following magnetic field enhancement. We infer that this phenomenon is due to the magnetostriction materials of nickel, which cause the nickel structure to impose a slight stretching strain on the ELPFG with the applied magnetic field.