Optical method for current measurement - uses magneto=optical interaction between field around wire and laser light passing through coiled optical fibre

摘要

The system uses a laser (3) producing a beam of light (21) which is linearly polarised. The light passes through a half-wave plate (4) before entering an optical cube (5). The cube splits the beam into two parts (22,23). One part of the beam is sent via further optical components (6,8) to one end of an optical fibre (2). The fibre is coiled around a former (1a) on the current carrying wire. The light passes through a fibre around the coil and emerges at the other end (2b) to be reintroduced into the optical system. Two signals are derived and compared by a differential amplifier (17) to determine the differential modulation between them. As a result of the magneto-optical effect between the current and the beam this provides a signal indicating the magnitude of the current.