Novel Fiber-Optic Sensor of High Electrical Alternating Currents

The novel sensor for measuring high electrical alternating currents is presented. The magnetic field induced by the ac-current excites dynamic strains of a multimode fiber (MMF), which are converted into the phase modulation of the light propagating through a fiber. The sensor consists of a permanent magnet, mechanical cantilever beam, MMF, and photorefractive adaptive interferometer. The permanent magnet and a MMF are both mounted at the free end of the cantilever beam and the static tensile stress is applied to MMF to achieve linear and reliable detection of the induced phase shifts. The phase shift is measured by an adaptive holographic interferometer which is based on the vectorial wave mixing in a CdTe photorefractive crystal.