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

•The current sensor with NCF shows high sensitivity in the previous work. On this basis, the current sensor based on FLRDS and bent-melt taper NCF is proposed. As far as I am concerned, it is proposed for the first time.•The current sensor shows high sensitivity, good repeatability and reversibility.•The sensitivity is 0.1161 μs /mA with the corresponding linearity R2 of 0.9926.•The sensitivity is higher than sensors with other optical fiber sensing probe in the FLRDS technology.