OPTICAL SENSORS

摘要

A Faraday-effect magneto-optic sensor comprises a light source (2), a polariser (8), a polarisation-maintaining efferent optic fibre (14) for conveying the plane-polarised light from the light source (2) and polariser (8) to a Faraday effect sensor (6) which includes a Faraday-effect transducer (9) which, in response to a magnetic field directed along the direction of light propagation within the transducer serves to change the plane of polarisation of the plane-polarised light by an amount which is proportional to the strength of the magnetic field. Light from the sensor (6) passes via a polarisation-maintaining afferent optic fibre (15), via a second polariser (10) acting as an analyser to a photodetector (3) which supplies an output signal to signal processing circuitry (4). In one embodiment, a respective gradient index lens is mounted between the optic fibres (14, 15) and the Faraday-effect sensor (6). The transducer comprises a rare-earth-doped iron garnet such as yttrium iron garnet. Such an optical sensor can be used to detect the existence of a partial electric discharge by sensing the magnetic field associated with this discharge.