We have developed a calibrated optical fiber Faraday rotation current sensor. A strong magnetic field in an optical fiber introduces circular birefringence, causing the plane of polarization of light to rotate by an amount proportional to the magnetic field. Faraday loops used in the past were nonlinear due to the stress-induced linear birefringence caused by bending the loop. This linear birefringence interfered with the Faraday rotation, yielding a complicated relationship between the current and detected light signal. We have found a way to overcome the effects of the unwanted linear birefringence and produce a calibrated current waveform. The calibration is limited only by the accurate knowledge of the Verdet constant of the optical fiber. Results of recent experiments as well as planned measurements will be presented.
B. T. Neyer,
L. E. Ruggles,
"Calibrated Faraday Current And Magnetic Field Sensor", Proc. SPIE 0566, Fiber Optic and Laser Sensors III, (3 January 1986); doi: 10.1117/12.949790; https://doi.org/10.1117/12.949790