Trinomial all-fiber current transformer

The invention relates to a trinomial all-fiber current transformer. Three sensing fiber loops are applied to trinomial current in a multiplexing one-drag-three all-fiber light path, but other optical fiber devices such as a light source, a polarization and phase modulator and a detector are multiplexed. The current transformer is also characterized in that: a measuring current sensing head part and a signal transmission part between a primary current side and a secondary current side adopt all-fiber structures. A light path structure only comprises one working light source, the light intensity of laser emitted from the light source is distributed by using a coupler and the same light source exists in a measuring optical fiber light path for the trinomial current, so that the light source consistency of a trinomial current measuring light path is ensured well.