By combining twisted optical sensing fiber and heterodyne phase detection of circular birefringence we have (a) overcome the distortion problem caused by residual linear birefringence in the Faraday rotation method of measuring enclosed current and (b) used only a single output detector without requiring intensity normalization. Resolution of 400 ampere-turns has been obtained in the hostile electromagnetic environment of a working thermonuclear fusion research device. The fiber was simply wound around the existing machine. The measured values are in excellent agreement with those of the electrical Rogowski coil installed when the machine was built.
© 1986 Optical Society of America
Original Manuscript: January 21, 1986
Published: June 1, 1986
George I. Chandler, P. R. Forman, F. C. Jahoda, and K. A. Klare, "Fiber-optic heterodyne phase-shift measurement of plasma current," Appl. Opt. 25, 1770-1774 (1986)