Electromagnetic field sensors are widely used in various areas. In recent years, great progress has been made in the optical sensing technique for electromagnetic field measurement, and varieties of corresponding sensors have been proposed. Types of magnetic field optical sensors were presented, including probes-based Faraday effect, magnetostrictive materials, and magnetic fluid. The sensing system-based Faraday effect is complex, and the sensors are mostly used in intensive magnetic field measurement. Magnetic field optical sensors based on magnetic fluid have high sensitivity compared to that based on magnetostrictive materials. Three types of electric field optical sensors are presented, including the sensor probes based on electric-optic crystal, piezoelectric materials, and electrostatic attraction. The majority of sensors are developed using the sensing scheme of combining the LiNbO3 crystal and optical fiber interferometer due to the good electro-optic properties of the crystal. The piezoelectric materials-based electric field sensors have simple structure and easy fabrication, but it is not suitable for weak electric field measurement. The sensing principle based on electrostatic attraction is less commonly-used sensing methods. This review aims at presenting the advances in optical sensing technology for electromagnetic field measurement, analyzing the principles of different types of sensors and discussing each advantage and disadvantage, as well as the future outlook on the performance improvement of sensors.

A microelectromechanical systems system (MEMS) electromagnetic swing-type actuator is proposed for an optical fiber switch in this paper. The actuator has a compact size of 5.1 × 5.1 × 5.3 mm3, consisting of two stators, a swing disc (rotator), a rotating shaft, and protective covers. Multi-winding stators and a multipole rotator were adopted to increase the output torque of the actuator. The actuator’s working principle and magnetic circuit were analyzed. The calculation results show that the actuator’s output torque is decisive to the air gap’s magnetic flux density between the stators and the swing disc. NiFe alloy magnetic cores were embedded into each winding center to increase the magnetic flux density. A special manufacturing process was developed for fabricating the stator windings on the ferrite substrate. Six copper windings and NiFe magnetic cores were electroplated onto the ferrite substrates. The corresponding six magnetic poles were configured to the SmCo permanent magnet on the swing disc. A magnetizing device with a particular size was designed and fabricated to magnetize the permanent magnet of the swing disc. The actuator prototype was fabricated, and the performance was tested. The results show that the actuator has a large output torque (40 μNm), fast response (5 ms), and a large swing angle (22°).

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Purpose This study aims to address the issue of high-precision measurement of AC electric field. An electro-optical sensor with high sensitivity is proposed for this purpose. Design/methodology/approach The proposed sensor combines electromagnetic induction and fiber Bragg grating (FBG) sensing techniques. It is composed of a sensing probe, a piece or stack of piezoelectric ceramics (PZT) and an FBG. A signal processing circuit is designed to rectify and amplify the induced voltage. The processed signal is applied to the PZT and the deformation of PZT is detected by FBG. Theoretical calculation and simulation are conducted to verify the working principle of the probe. The sensor prototype is fabricated and its performance is tested. Findings The results of this study show that the sensor has good linearity and repeatability. The sensor sensitivity is 0.061 pm/Vm−1 in the range from 250 to 17,500 V/m, enabling a measurement resolution of electric field strength of 16.3 V/m. The PZT stack is used to enhance the sensor sensitivity and the resolution can be improved up to 3.15 V/m. Originality/value A flexure hinge lever mechanism is used to amplify the deformation of PZT for further enhancement of sensitivity. The results show that the proposed sensor has high sensitivity and can be used for the accurate measurement of an electric field. The proposed sensor could have potential use for electric field measurement in the power industry.