Temperature Compensated Fiber-Optic Current Sensor

摘要

In a fiber-optic current sensor, a 22.5° Faraday rotator, which is part of the sensing fiber coil, determines the working point of the sensor. The coil is operated with substantially linearly polarized light or incoherent substantially left and right circularly polarized light waves. In one arrangement, a polarization beam splitter generates two optical signals that vary in anti-phase with changing current. A signal processor determines the current from the two anti-phase signals. Appropriately detuned and oriented fiber-optic half-wave or quarter-wave retarders before the fiber coil are used to reduce or cancel the adverse effects of temperature and bend-induced birefringence on the measurement signal. Moreover, the temperature may be derived from the difference in the bias of the anti-phase signals and may be used to cancel temperature effects in the signal processor.

主权项

1. A current sensor comprising:
a light source, a first linear polarizer receiving light from the light source and generating polarized light, and a sensor head with
a retarder receiving light from the first linear polarizer and having a retardation of 90°+Δρ+N·180° or 180°+Δρ+N·180° with retarder detuning Δρ≠0 and N being an integer number ≧0,wherein the retarder detuning |Δρ| is in a range of 1° to 30° and serves for reducing a temperature-dependence in the measurement signal,a sensing fiber arranged to receive light from the retarder, wherein the sensing fiber is adapted to be looped at least once around a conductor carrying a current to be measured,a mirror arranged to receive light from the sensing fiber, anda Faraday rotator arranged between the retarder and the mirror, wherein the Faraday rotator rotates the light by (22.5°+M·45°)±10°, with M being an integer number ≧0,the current sensor further comprising at least one detector adapted to measure at least one signal of light returning from the sensor head through the first linear polarizer.