Temperature compensated fiber optic magnetic sensor based on the combination interference principle

Abstract

In this paper, a highly sensitive temperature compensated fiber optic magnetic field sensor by Sagnac and Mach–Zehnder combination interference (SMZI) is proposed and verified. The sensing structure relies on microstructured exposed core fiber (ECF) filled with ethanol and magnetic fluid (MF). The refractive index of MF and ethanol is affected by the magnetic field and temperature (MFT). SMZI is based on the multimode and birefringence characteristics of ECF. The measurement principle is that the spectra of Sagnac interference and Mach–Zehnder interference have respective sensitivities to the MFT. The magnetic sensitivity can reach 1.17 nm/mT, and the temperature sensitivity is up to –1.93 nm/°C. At the same time, the sensor has good repeatability and low detection limits of 0.41 mT and 0.25°C, respectively. It not only solves the cross-influence of temperature but also makes the spectral analysis more intuitive. The sensor has a broad development prospect in the application of MFT detection.

Research Progress on Magneto-Refractive Magnetic Field Fiber Sensors

“…When the MF changes the optical path difference of the loop, the interferometer spectrum will shift. Yu et al [ 44 ] proposed magnetic field sensors based on SI, with the principle of the birefringence effect occurring in an Exposed-Core Fiber (ECF). Owing to the particular structure of the ECF ( Figure 5 b), MF and alcohol can make enough contact with the Evanescent Field of the ECF, raising sensor sensitivity up to 117 pm/Oe.…”

“…[ 43 ], 2021, The Optical Society) and ( b ) SI (reprinted with permission from Ref. [ 44 ], 2022, The Optical Society).…”