A Novel Current Sensor Based on Magnetic Fluid and Fiber Loop Cavity Ring-Down Technology

A novel current sensing system, based on magnetic fluid (MF) film and fiber loop cavity ring-down (CRD) technology, is proposed and demonstrated for the first time. In the sensing system, a MF film whose loss coefficient can be affected by magnetic field is inserted in the ring cavity as the sensitive device. The MF film is made by etching center of two glass slides and sealing MF with a volume concentration of C = 3.6% in it. This structure is used as the sensitive device in the ring cavity. In this paper, a fiber loop CRD sensing system has been established for electric current measurement, and a theoretical model for optimizing coupling ratio of the two couplers in the ring cavity has been presented. The performances of the electric current sensor are evaluated by applying different magnetic fields generated by current to detect decay constants. It can be concluded from the experimental results that a magnetic field measurement sensitivity of 0.00033 T/μs is reached, corresponding to a current measurement sensitivity of 3.3 mA/μs. The current measurement method based on CRD technology and MF provides a new way for research and applications in the field of modern electrical engineering.