Magnetic field sensor based on twisted fiber and magnetic fluid

A magnetic field sensor based on twisted single mode fiber and magnetic fluid (MF) is proposed and demonstrated. The sensor consists of two twisted points on a single mode fiber introduced by flame-heated and rotation treatment. Cladding modes are excited at the first twisted point and part of them are coupled back to the fiber core at the second twisted point, forming an inline Mach-Zehnder interferometer. Then the structure was inserted into a MF-filled capillary for magnetic field sensing. Owing to the refractive index tunable characteristic of the MF, the destructive interference wavelength will shift as the magnetic field intensity varies. Experimental result shows that a sensitivity of 55.5pm/Oe is achieved for static magnetic field measurement ranging from 20-120 Oe.