Ultrahigh-sensitivity vector magnetic field sensor based on radio-frequency interferometer with magnetostrictive alloy

An ultrahigh-sensitivity vector magnetic field sensor is developed in accordance with radio-frequency interferometer and magnetostrictive alloy. The reflected light signals of two fiber Bragg gratings (FBGs) with different center wavelengths act as the optical carrier. After being intensity modulated by a radio-frequency signal, the optical carriers are transferred to the sensing head, which contains two magnetostrictive alloy-FBGs (MA-FBGs). The center wavelengths of MA-FBGs locate at the falling edge and rising edge of the FBGs, respectively. In the effect of magnetic field, the MA-FBGs act as two tunable optical filters. Hence, the contrast ratio of the RF interferogram relates the optical powers of two carriers as well as the magnetic field. Benefiting from the opposite power variation of two optical carriers under the magnetic field, an ultrahigh-sensitivity vector magnetic field sensor is implemented. The direction sensitivity reaches 0.368 dB/deg. The developed method shows several superiorities, which cover excellent sensitivity, compact size, low-priced characteristic, as well as simple preprocessing, such that it can arouse wide attention in vector magnetic field sensing.