High sensitivity and large measurement range magnetic field micro-nano fiber sensor based on Mach-Zehnder interference

High sensitivity and large measurement range magnetic field micro-nano fiber (MFM-NF) sensor based on Mach-Zehnder interference has been proposed and demonstrated. This sensor is composed of micro-nano optical fiber (MNF) and magnetic fluid (MF). MNF is fabricated with rapidly changed cone region and small diameter micro-nano region, the core mode will be coupled to the cladding duo to the small enough diameter of the MNF, and the core mode and the cladding mode will be form Mach-Zehnder interference. The change of magnetic field leads to the change of MF refractive index, and the refractive index near the micro-nano region strongly affects the mode interference. Under the magnetic field increased, the magnetic field sensitivity of the sensor is up to 69 pm/Gs in the range of 50 ∼ 200 Gs. The linearity was 0.9952. Under the magnetic field decreased, the linear correlation is 0.9942 in the range of 200 ∼ 0 Gs, and the magnetic field sensitivity is 29 pm/Gs. The sensor has the advantages of easy fabrication, low cost and simple structure, and it would be have a wide application prospect in the field of magnetic field sensing.