Highly Sensitive Fiber‐Optic Intrinsic Electromagnetic Field Sensing
Arnaldo Leal‐Junior, Camilo A. R. Díaz, Anselmo Frizera, Heeyoung Lee, Kentaro Nakamura, Yosuke Mizuno, Carlos Marques
Abstract
Fiber‐optic sensing is resistant to electromagnetic interference; therefore, electromagnetic field sensing using fiber‐optic sensors is challenging. Herein, the first demonstration of fiber‐optic intrinsic electromagnetic field sensing based on modal interferometry with the highest reported sensitivity is presented (here, to be intrinsic means that the magnetic field interaction occurs only within the optical fiber, where there is no use of magnetic fluids or extrinsic structures). A fused polymer optical fiber (POF) is connected to two silica single‐mode fibers (SMFs) through an UV‐curing resin. Another interferometer with a nonfused POF is also fabricated, and the transmitted spectra of both the interferometers are compared in the presence of an electromagnetic field (0–240 mT). The results show the insensitivity of the nonfused POF interferometer and a mean sensitivity of 16.7 pm mT −1 for the fused POF interferometer, which presents a tenfold increase by changing the fused POF length from 2 to 5 cm, resulting in a sensitivity of 113.5 pm mT −1 . The proposed intrinsic electromagnetic field sensor has the potential of measuring magnetic field intensities as low as 45 μT (considering its high sensitivity) with possibility of further increase with small changes in the signal acquisition components.