Methods and apparatus for measuring a current

Optical fiber-based measuring equipment configured for measuring a first current circulating through a first conductor, the equipment comprising:

• an interrogator including:
• a first light emitter configured to emit a first light pulse;
• a first light receiver;
• a first coupler to which each of the first light emitter and first light receiver is optically coupled,
• a second light emitter configured to emit a second light pulse,
• a second light receiver:
• and
• a second coupler to which each of the second light emitter and second light receiver is optically coupled;
• a sensing portion located in proximity to the first conductor, the sensing portion comprising:
• a first branch having a first polarizer and a first rotator located downstream the first polarizer,
• a second branch having a second polarizer,
• a first sensing branch including a first sensing section arranged close to the first conductor and a first mirror located downstream the first sensing section,
• a third coupler having first and second inputs and a first output, the first branch and the second branch being respectively optically coupled to the first and second inputs, and the first sensing branch being optically coupled to the first output;
• a first single-mode optical fiber that optically couples the first branch to the first coupler;
• and
• a second single-mode optical fiber that optically couples the second branch to the second coupler;
• the optical-based measuring equipment being arranged such that when the first light pulse is emitted by the first light emitter, the first light pulse is caused to be delivered towards the first mirror sequentially through the first coupler, the first single-mode optical fiber, the first branch and the first sensing branch, and to cause the first light pulse to be modified in the first sensing section depending on the current circulating through the first conductor to produce a first modified first light pulse;
• the optical-based measuring equipment being arranged such that when the second light pulse is emitted by the second light emitter, the second light pulse is caused to be delivered towards the first mirror sequentially through the second coupler, the second single-mode optical fiber, the second branch and the first sensing branch, and to cause the second light pulse to be modified in the first sensing section depending on the current circulating through the first conductor to produce a first modified second light pulse;
• the optical-based measuring equipment being arranged to cause the first mirror to reflect the first modified first light pulse toward the second receiver sequentially through the first sensing branch, the second branch, the second single-mode optical fiber and the second coupler;
• the optical-based measuring equipment being arranged to cause the first mirror to reflect the first modified second light pulse toward the first receiver sequentially through the first sensing branch, the first branch, the first single-mode optical fiber and the first coupler.