Measurement Of Megampere Currents With Optical Fibers

We have used fiber optic sensors routinely to measure multi-megampere currents. The sensors are low noise, absolutely calibrated, and electrically decoupled from the pulsed power source. Polarized light from a HeNe laser is guided past the current carrier by a single-mode, low-birefringence fiber. The magnetic field from the current causes a Faraday rotation of the light polarization which is detected by a polarization analyzer and photo-diode at the end of the fiber. We observe a rotation of about 250°/MA ± 5%, slightly less than the Verdet constant for non-birefringent silica glass. We find that highly birefrin-gent (polarization preserving) optical fibers do not work in this application. We are now trying to ruggedize the sensor for field use with high-explosive-driven current sources by using a diode laser and single mode fiber couplers to replace the laboratory system of lenses and spatial filters.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.