Fiber-optic current sensor

An optical current sensor having a reflection interferometer which has a fiber-optic supply lead and a coil-shaped optical sensor element, the sensor element being connected with a first end to the fiber-optic supply lead and being provided at a second, free end with a reflector, having at least one phase modulator for modulating differential phases of two polarized waves propagating in the fiber-optic supply lead, and a detector, wherein the fiber-optic supply lead has two fiber arms which interconnect a detector-side and a sensor-side coupler, in that the at least one phase modulator is arranged in one of these two fiber arms, in which case it modulates the differential phase of two oppositely directed waves polarized parallel to one another, and wherein one fiber arm is provided with a means for changing the direction of polarization such that optical waves with orthogonally linear polarizations propagate in a segment of the supply lead fiber adjoining the sensor-side coupler, wherein the means for changing the direction of polarization is a 90° splice.