ヒューズ後のプラスチック光ファイバを用いて超高感度で磁界を計測した国内外5大学【芝浦工業大学・横浜国立大学・東京工業大学・エスピリトサント連邦大学（ブラジル）・アヴェイロ大学（ポルトガル）】との研究成果が Advanced Photonics Research に掲載されました。
A. Leal-Junior, C. Díaz, A. Frizera, H. Lee, K. Nakamura, Y. Mizuno, C. Marques, “Highly sensitive fiber‐optic intrinsic electromagnetic field sensing,” Adv. Photon. Res., vol. 2, no. 1, 2000078 (2021).
We present the first report on reflectometric optical fiber sensing based on mechanically induced cascaded long-period grating (LPG) structure. This method utilizes in-house designed mechanical casings and a bare fiber. When a fiber is sandwiched between the casings and pressed by tightening screws, an LPG is induced due to a photo-elastic effect. By exploiting Fresnel refection at a fiber end, a cascaded LPG structure can be implemented using a single LPG, enabling reflectometric configuration. When this sensor is subjected to external physical processes, the attenuation bands change clearly, and their shift can be used for non-destructive evaluations. We show experimentally that this sensor can measure loads of up to 10 N without producing any permanent change in the fiber properties, indicating its pressure sensing capability. We also show that this sensor can potentially measure strain and temperature. In our experiments, the strain and temperature sensitivities are 9.4 nm/% and 0.045 nm/°C, respectively.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.We present the first report on reflectometric optical fiber sensing based on mechanically induced cascaded long-period grating (LPG) structure. This method utilizes in-house designed mechanical casings and a bare fiber. When a fiber is sandwiched between the casings and pressed by tightening screws, an LPG is induced due to a photo-elastic effect. By exploiting Fresnel refection at a fiber end, a cascaded LPG structure can be implemented using a single LPG, enabling reflectometric configuration. When this sensor is subjected to external physical processes, the attenuation bands change clearly, and their shift can be used for non-destructive evaluations. We show experimentally that this sensor can measure loads of up to 10 N without producing any permanent change in the fiber properties, indicating its pressure sensing capability. We also show that this sensor can potentially measure strain and temperature. In our experiments, the strain and temperature sensitivities are 9.4 nm/% and 0.045 nm/°C, respectively.