All-Fiber Magnetic Field Sensor Based on Hollow Optical Fiber and Magnetic Fluid

A compact all-fiber magnetic field sensor is achieved by using Mach-Zehnder interferometer based on the hollow optical fiber (HOF) and the magnetic fluid (MF). The HOF is sandwiched between two single mode fibers (SMFs), which form an SMF-HOF-SMF (SHS) structure. Then, the SHS structure is immersed in MF to sense the magnetic field strength. The magnetic field assisted tunable refractive index of MF is exploited to realize the sensor. As a result, the magnetic field strength can be obtained by monitoring the wavelength shift of the SHS structure. The maximum magnetic field sensing sensitivity of -170 pm/Oe is obtained at the wavelength around 1580 nm. Besides, an intensity sensitivity of -0.21268 dB/Oe is also achieved.