Patent ID: 8624579

Claim:
A fiber-optic current sensor for sensing an electric current carried in an electric conductor ( 18 ), the fiber-optic current sensor comprising an optical section and an electronic section; wherein the optical section comprises: a light source ( 1 ); a directional coupler ( 2 ) with a first port ( 2 A) and a second port ( 2 B), each port comprising a first arm ( 2 A 1 , 2 B 1 ) and a second arm ( 2 A 2 , 2 B 2 ); a radiation polarizer ( 3 ) with a first port ( 3 A) and a second port ( 3 B); a polarization modulator ( 4 ) with a first port ( 4 A) and a second port ( 4 B), a fiber line ( 17 ) coupled to a current-sensing fiber loop ( 11 ) having a first end and a second end; a radiation reflector ( 10 ); a photodetector ( 22 ); wherein one arm ( 2 A 1 ) of the first port of the directional coupler ( 2 ) is coupled to the light source ( 1 ) while the other arm 2 A 2 of the first port of the directional coupler ( 2 ) is coupled to the photodetector ( 22 ); one arm ( 2 B 1 ) of the second port of the directional coupler ( 2 ) is coupled to the first port ( 3 A) of the radiation polarizer; the second port ( 3 B) of the radiation polarizer is coupled to the first port ( 4 A) of the polarization modulator; the polarization modulator ( 4 ) comprises a magneto-sensitive element ( 5 , 26 ), around which a solenoid ( 6 ) is wound; the current-sensing fiber loop ( 11 ) is made of magneto-sensitive optical fiber with an embedded linear birefringence; and wherein the electronic section comprises: a signal generator ( 21 ) configured to drive the solenoid ( 6 ); and a signal processing ( 23 ) unit configured to receive an electrical signal from the photodetector ( 22 ).