OPTICAL FIBER CURRENT SENSOR

PROBLEM TO BE SOLVED: To expand a measurable range of a current value with a simple configuration in an optical fiber current sensor.SOLUTION: The optical fiber current sensor is equipped with: a sensor fiber 11; a first analyzer 14A on which linearly polarized light propagated through the sensor fiber 11 impinges while an optical bias is set to zero; a second analyzer 14B on which linearly polarized light propagated through the sensor fiber 11 impinge while the optical bias is set to δ; light-receiving elements 15-1, 15-2 for photoelectrically transducing light passing through the first analyzer 14A; light-receiving elements 15-3, 15-4 for photoelectrically transducing light passing through the second analyzer 14B; and a signal processing section 16 for obtaining a Faraday rotation angle by determining a quadrant where the Faraday rotation angle is located on the basis of a relation in a level of signals Px, Py obtained by the light-receiving elements 15-1, 15-2 and signals Pδx, Pδy obtained by the light-receiving elements 15-3, 15-4.