Optical Liquid-Crystal Magnetic Field Sensor With Temperature Compensation

This article presents a reflective Fabry–Perot (FP) dual-parameter sensor utilizing nematic liquid crystal (LC) for high-sensitivity temperature and magnetic field measurement. The FP interferometer is comprised an incident single-mode fiber with a flat-cut end, and a reflection flat fiber end with silver coated. The incident fiber cascaded with a fiber Bragg grating (FBG). The LCs are injected into the FP cavity. All of the structures are packaged in a capillary tube to construct a magnetic sensor. Due to the directional nature of LC molecules, they are sensitive to magnetic fields. The birefringence of the LC produces a Vernier spectrum, which further enhances the magnetic field sensitivity. The experimental results show that the magnetic sensitivity of the sensor would reach 3.12 nm/Gs with good linearity in a measurement range of 0–30 Gs, the sensor would magnetically saturate once the magnetic field exceeds 100 Gs. The Vernier peaks also have a temperature sensitivity of 12.53 nm/°C. The temperature can be measured with the aid of the FBG. The FBG exhibits strong anti-interference properties to the magnetic field. This sensor possesses a simple structure, high sensitivity to the magnetic field, and the property of temperature compensation, hence it would be a cost-effective and reliable candidate for practical magnetic sensing applications.