Abstract: An optical torque sensor for incorporation in a vehicle steering system comprises a light-emitting diode (LED) 1, a light sensor 2 which receives a light signal, a signal processor for receiving output signals from the light sensor 2, and a light-transmitting medium which alters the direction of propagation of light propagating through the medium to an extent which is dependent on the torque applied to the medium. The medium is defined by a generally cylindrical body 5 which is attached to input and output ends 7 and 8 of a torsion bar 10. In one construction, the body is formed of a plurality of optical fibres 6 or a plastics material having polarised strata along the length of the cylinder. In an alternative construction, the medium is a material having a refractive index which is dependent on the torque applied to the medium.