A temperature self-compensating fiber-optic magnetic field sensor based on Mach-Zehnder interferometer and Vernier effect

A temperature self-compensating fiber-optic magnetic field sensor based on Mach-Zehnder interferometer (MZI) and Vernier effect was proposed. The sensor consisted of MZIs connected in parallel. The hollow-core fiber (HCF) cladding of two MZIs was etched by hydrofluoric acid, and wrapped with magnetic fluid (MF) and polydimethylsiloxane (PDMS), respectively. The magnetic field sensitivity of MZI1 was improved by etching the HCF cladding. The maximum detection sensitivity of MZI1 was −161.1 pm/mT, and the temperature cross-sensitivity was 0.647 mT/°C. MZI2 was designed to be insensitive to magnetic fields, while its temperature sensitivity was similar to that of MZI1. By adjusting the parameters of two MZIs, the sensor could produce a Vernier effect with changes in magnetic field, increasing the sensitivity of magnetic field detection. Since the temperature response of two MZIs was similar, the sensors could produce a reduced Vernier effect with temperature changes, eliminating temperature crosstalk, and achieving temperature self-compensation. The experimental results demonstrated that the magnetic field sensitivity of the sensor was −654.7 pm/mT, which was 4.1 times higher than that of MZI1. The temperature crosstalk sensitivity was only 0.029 mT/°C, which was 22.3 times lower than that of MZI1. The proposed sensor enhanced the utilization efficiency of the Vernier effect through the special design of MZI2, which provided a new strategy for the Vernier effect in the fiber-optic magnetic field measurement domain.