Abstract: A magneto-optic sensor for oilfield application, the sensor (1, 1?, 101, 101?) receives an incident beam IB, IBA, IBB, IBC, IBD and comprises a polarizing element (3, 103) for providing a determined state of polarization beam and a Faraday rotator (4, 104) for providing a response beam having a modified state of polarization. The sensor provides a response beam (RB, RBA, RBB, RBC, RBD having an intensity dependent on an external magnetic field representative of a particular characteristic of a well-bore casing CC, CR applied on the Faraday rotator (4, 104).

Abstract: A magnetooptic read head including a magnetooptic transducer with a multilayer structure with at least one thin magnetic layer with a magnetooptic effect, at least one layer made of nonmagnetic material and having a predetermined wear coefficient, and a layer with good magnetic permeability for closing a magnetic circuit. The layer with good magnetic permeability includes alternating first sublayers made of a magnetic material with good magnetic permeability and second sublayers made of a material having a wear coefficient substantially equivalent to the wear coefficient of the layer made of a nonmagnetic material.