Fiber Bragg Grating Sensor for Electric Field Measurement in the End Windings of High-Voltage Electric Machines

This paper reports proof-of-principle of an optical fiber Bragg grating (FBG) operating as an electric field sensor. The system is based on a semiconductor diode laser, emitting around 1577.5 nm that interrogates the fiber sensor around its maximum reflectivity point. The application of a strong electric field causes a small variation of the optical path length of the waveguide due to electrostriction and thus perturbs the grating peak reflectivity wavelength. Calibration and dynamic range tests are performed using a parallel-plate capacitor to create a variable electric field (1-100 kV/cm). A great potential is pointed out in view of possible field applications for voltage graduation in power generators.