Patent ID: 7075286

Claim:
An optical current sensor comprising: a detector; a reflection interferometer, which has a fiber-optic lead and coil-type optical sensor, the fiber-optic lead having a first fiber branch and a second fiber branch, which two fiber branches are connected to one another via a coupler on the sensor side, the first fiber branch being connected to a light source and the second fiber branch being connected to the detector, and the sensor being connected to the lead at a first end and being provided with a reflector at the second end; and a first means for phase modulation of a differential phase of two mutually orthogonally polarized optical waves which propagate in the lead; wherein the first fiber branch is designed as a polarization-maintaining first fiber branch for two forward-travelling, mutually orthogonally polarized waves; the second branch is designed as a polarization-maintaining second fiber branch for two backward-travelling mutually orthogonally polarized waves; the first means for phase modulation is functionally connected to one of the first and second fiber branches; and the optical lengths of the fiber branches are, within the coherence length of the light source, identical.