Intensity-interrogated magnetic sensor based on S-tapered and multimode fiber integrated with ferrofluids.

In this study, a high-sensitivity intensity-interrogated fiber sensor integrated with ferrofluids is proposed for the measurement of a weak magnetic field (MF) with resolved temperature cross-sensitivity. The MF sensor is fabricated simply by an offset tapering single-mode fiber concatenated with a multimode fiber (MMF), which is then encapsulated into a capillary tube filled with ferrofluids. In the presence of MMF, stronger mode coupling could be achieved over the S-tapered fiber region. Its spectral response to variations in the applied MF intensity and ambient temperature have been investigated in detail. The proposed sensor shows a high MF sensitivity up to -0.1130/ for the measurement range of 40 to 120 Oe, which, to our best knowledge, is higher than other previously reported MF sensors. And moreover, the measurement errors caused by temperature cross-sensitivity have been corrected by using a sensing matrix for the temperature range of 25°C to 35°C. Our proposed MF sensor possesses the advantages of high sensitivity, low cost, and applicability for applications in weak MF measurements.