Method and apparatus for measuring the current circulating through a conductor

A method for measuring a current circulating through a conductor with an optical fiber-based measuring system,

• the measuring system including:
• an interrogator including a first emitter, a second emitter, a first receiver, and a second receiver, the first and second emitters respectively configured to emit first and second light pulses;
• a sensing portion optically coupled to the interrogator and configured to be arranged in proximity to the conductor, the sensing portion including:
• a first input branch optically coupled to the first emitter, the first input branch including a first polarizer and a fiber twist located after the first polarizer:
• a second input branch optically coupled to the second emitter, the second input branch including a second polarizer;
• a splitter including first and second inputs and first and second outputs, the first and second input branches being respectively optically coupled to the first and second inputs;
• a first sensing branch optically coupled to the first output of the splitter and including a first optical fiber winding and a first Faraday mirror located after the first optical fiber winding, the first optical fiber winding configured to be positioned adjacent the conductor and having a first number of turns, and wound in a first direction;
• and
• a second sensing branch optically coupled to the second output of the splitter and including a second optical fiber winding, a second Faraday mirror located after the second optical fiber winding and a delaying element located between the second optical fiber winding and the second Faraday mirror, the second optical fiber configured to be positioned adjacent the conductor and having a second number of turns that is the same as the first number of turns, and wound in a second direction opposite the first direction
• the method comprising:
• emitting a first light pulse from the first emitter, a first portion of the first light pulse reaches the first sensing branch through the first input branch and the splitter, travels along the first sensing branch through the first optical fiber winding and is modified depending on the current circulating through the conductor, a modified first portion of the first light pulse being received in the second receiver from the second input branch, a second portion of the first light pulse also reaches the second sensing branch through the first input branch and the splitter, travels along the second sensing branch through the second optical fiber winding and is modified depending on the current circulating through the conductor, a modified second portion of the first light pulse being received by the second receiver from the second input branch;
• emitting a second light pulse from the second emitter, a first portion of the second light pulse reaches the first sensing branch through the second input branch and the splitter, travels along the first sensing branch through the first optical fiber winding and is modified depending on the current circulating through the conductor, a modified first portion of the second light pulse being received by the first receiver from the first input branch, a second portion of the second light pulse reaches the second sensing branch through the second input branch and splitter, travels along the second sensing branch through the second optical fiber winding and is modified depending on the current circulating through the conductor, a modified second portion of the second light pulse being received by the first receiver from the first input branch;
• the current circulating through the conductor being determined by combining the modified first portion of the first light pulse modified in the first sensing branch and received by the second receiver, the modified first portion of the second light pulse modified in the first sensing branch and received by the first receiver, the modified second portion of the first light pulse modified in the second sensing branch and received by the second receiver, and the modified second portion of the second light pulse modified in the second sensing branch and received by the first receiver.