To increase Verdet constant and the number of passes of light around the conductor are the main methods for increasing sensitivity of the Faraday effect optical current transducers (OCTs). In this paper, the comparative measurement is taken to eliminate the influence of temperature when a high Verdet constant ferromagnetic material is used. Moreover,a dual-ring and a multiple-ring optical path structure are designed Theexperimental results of the dual-ring structure are presented.