In the paper,The research progress of current sensor was introduced.And the working principle,characteristics and
disadvantages were analyzed.We explore optical current sensor based on Fiber Loop Ring Down Spectroscopy
(FLRDS), The sensing system consists of a fiber sensor head and a typical fiber loop ring down system including a
pulsed VCSEL laser diode at 850 nm,multimode fiber couplers,multimode fiber loop,photo-receiver and high-speed data
acquisition and signal processing. The current sensor is demonstrated with a resolution of 0.05 A ,the sensor system's
good linear responses,stability,repeatablity,sensitivity are also explored.