Abstract
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.
Highlights
Magnetic field sensors include many aspects of mechanical and electronic techniques
When light source launched into the notched long-period fiber grating (NLPFG), a guided core mode would interact with the NLPFG and is converted into cladding modes that are lost owing to absorption and scattering [22]
NLPFGisisaaloss losstunable tunablefilter filterbased basedon onperiodic periodicrefractive refractiveindex indexmodulation modulationcaused causedby by NLPFGisisplaced placedunder underaxial axialloading, loading,ititgenerates generatesaaperiodic periodicstrain strainfield field external owing to the expanded cross section area, which subsequently affects the refractive index periodic owing to the expanded cross section area, which subsequently affects the refractive index periodic distributionofof optical fiber produces an attenuated loss dipspectrum
Summary
Magnetic field sensors include many aspects of mechanical and electronic techniques. In terms of the applications for which such sensors are used, there is a clear and continuous trend toward using sensors of smaller size, lower energy consumption, and lower cost to achieve similar performance [1].Fiber-optic based technology possesses various advantages that can be beneficial in achieving that aim, because optical fiber sensors are light weight, immune to electromagnetic interference, resistant to corrosion and high temperatures, and are electrically passive when operating while requiring only limited power consumption [2,3]. In terms of the applications for which such sensors are used, there is a clear and continuous trend toward using sensors of smaller size, lower energy consumption, and lower cost to achieve similar performance [1]. LPFG consists of periodic refractive index variations with periods of 100–1000 μm [4,5]. LPFG promotes the coupling between a propagating core mode and a cladding mode to provide an attenuation loss band, which has characteristics conducive to sensor and communication applications [6], including gain flattening filtering [7], sensing for strain [8], sensing for temperature [9,10,11], and sensing variations in refractive index [12,13]
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