Abstract
We present a new photonic magnetic sensor that can yield information on the spatial angle of rotation of the sensor within a given static magnetic field that based upon an optical fiber platform that has a wavelength-encoded output and a demonstrated sensitivity of 543 pm/mT. This optical fiber magnetic field sensor combines a conventional, UV-laser inscribed long period grating (LPG) with a magnetostrictive material Terfenol-D that coats and fills 50-μm micro-slots running adjacent and parallel to the fiber central axis. The micro-slots are produced using a femtosecond laser and selective chemical etching. A detection limit for a static magnetic field strength of ±50 μT is realized in low strength DC magnetic field (below 0.4 mT), this performance approaches the Earth’s magnetic field strength and thus, once optimized, has potential for navigation applications. Our method addresses the major drawback of conventional sensors, namely their inadequate sensitivity to low strength, static magnetic fields and their inability to provide information about the orientation and magnitude.
Highlights
There is significant interest in detecting and monitoring electromagnetic fields (EMF) generated in a number of industries, for applications related to process control, electric field monitoring in medicine, ballistic control, electromagnetic compatibility measurements and the potential health risks associated with environmental exposure to overhead power cables [1,2]
We present here a new optical fiber magnetic field sensor, comprising a conventional UV-laser inscribed long period grating (LPG) adjacent to 50-m long micro-slots that are located parallel to the fiber central axis
This approximation assumes that the propagation constants already incorporate the shape birefringence, and the Terfenol-D stressinduced birefringence, caused by the radial generated strain by the Terfenol-D monoliths in the presents of static magnetic field, can be calculated using the approach given in REF 28, which includes the assumption that stress contribution wavelength dependence P is attributed to chromatic dispersion of the stress optical coefficient given in REF 28, the stress birefringence nstress and polarization dispersion P: nstress = PSmax and P
Summary
There is significant interest in detecting and monitoring electromagnetic fields (EMF) generated in a number of industries, for applications related to process control, electric field monitoring in medicine, ballistic control, electromagnetic compatibility measurements and the potential health risks associated with environmental exposure to overhead power cables [1,2]. Allsop et al / Sensors and Actuators A 269 (2018) 545–555 direction of the magnetic field, generating a longitudinal strain within the optical fiber itself [3,13,14,15] All of these fiber optic sensors have several operating deficiencies, principally, their poor performance leads to an inability to detect low static magnetic field strengths. The fiber was coated, and the micro-slots filled, with TerfenolD, a magnetostrictive material, by using sputtering technology This new optical fiber magnetic field sensor has a very high maximum spectral sensitivity to B-field ( / B of −543 pm/mT), an optimum resolution of ±50 T for magnetic field strengths below 0.4 mT and a resolution of ±100 T above 1 mT. The resolution of this type of fiber optic magnetometer in low strength DC magnetic field is ±50 T which is approaching the values of the earth’s magnetic field (25–65 T)
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