In-line Michelson interferometer based on microspherical structure for magnetic field applications

We experimentally demonstrated a scheme for the magnetic field measurement based on an in-line Michelson interferometer (MI) and magnetic fluid (MF). The tip packaged technology of a Michelson interferometer is proposed. The sensor is composed of microspherical structure, single-mode fiber (SMF), hollow-core fiber (HCF), quartz tube, and MF. Since the refractive index of the MF will be changed with the intensity of the magnetic field, the effective refractive index (ERI) of the cladding can be changed, which leads to correlative moves of the reflection spectrum. The magnetic field sensitivity of -118.7 pm/mT is obtained in the magnetic range from 1.36 to 11.8mT. We present a sensing structure, compared with other sensors, that has the advantages of simple, compact, and easy integration. The proposed sensor is expected to offer significant potential for detecting weak magnetic fields.