A Notched Long-Period Fiber Grating Magnetic Field Sensor Based on Nanoparticle Magnetic Fluid

In this paper, we propose using an inductively coupled plasma (ICP) etching technique to fabricate a notched long-period fiber grating (NLPFG) for magnetic sensing application. An optical fiber magnetic field sensor based on NLPFG filled with nanoparticle magnetic fluid is proposed and demonstrated. The magnetic fluid nanoparticles were attached on the grating structure section and used as a magneto-optical sensing layer to measure magnetic flux density. The external applied magnetic flux density ranged from 0 to 27.74 mT. As the magnetic flux density was increased, the spectra of the NLPFG were changed. The resonant wavelength of the attenuation band did not shift obviously, but the transmission loss of the resonant dip was increased by 3.48 dB from −19.41 dB to −15.93 dB. The experimental results indicated that the sensitivity of the sensor is approximately 0.125 dB/mT.