Highly sensitive current sensor based on fiber loop Ring-Down spectroscopy and Bent-Annealed taper No-Core fiber surrounded by magnetic fluid

A novel current sensing system based on fiber loop ring-down spectroscopy (FLRDS) and bent-annealed taper nocore fiber (NCF) immersed in magnetic fluid (MF) is proposed and demonstrated for the first time. Due to the sensitivity of the absorption coefficient and refractive index of MF to the magnetic field, the ring-down time of the system changes with the change of the magnetic field determined by the applied current. Therefore, the measurement of current can be realized by monitoring the ring-down time. A bent-annealed taper NCF structure immersed in MF is inserted in the ring cavity serving as the sensing head, which greatly enhances the evanescent field effect and improves the sensitivity of current sensing. A current sensor measurement sensitivity of 0.1161 mu s/mA is achieved as the NCF is annealed and bent with a waist diameter of 20 mu m and bent to 60 degrees in the measurement range of 0-600 mA. The current sensor based on FLRDS technology and bent-annealed taper NCF immersed in MF has made a great contribution to the research and application in the field of modern electrical engineering.