Magneto-optic torque measuring system with temperature compensation

A system for measuring the torque of a rotating shaft (70) in which a magneto-optic material (34) is subjected to a saturating magnetic field from a magnet (32). Ferrous elements (40, 44) about the periphery of the rotating shaft cause modulation of the magnetic field applied to the magneto-optic material (34). The rotation of the linear polarization vector of light passing through the magneto-optic material, when the material is magnetized to the saturation level, changes in accordance with temperature. Thus, the output signal varies in accordance with the temperature of the shaft. The passage of the ferrous elements modulates the optic signal output from the magneto-optic material and the phase changes relate to the shaft twist and hence to the torque applied to the shaft. Thus, a temperature compensated torque measurement is derived.