HIGH-SPEED FIBEROPTIC SENSOR FOR MAGNETIC-FIELD MAPPING

A fiber-optic sensor was fabricated with a magnetostrictive multilayer thin-film coating synthesized to have a combination of properties fav orable for resolving mm scale inhomogeneities in low level magnetic fi elds (similar to 100 mOe) varying at MHz rates. High-frequency detecti on was achieved by mixing signal and local oscillator fields varying a t frequencies f and f + f(mr)/2, into the mechanical resonance of the sensor at f(mr). These sensors are expected to be useful for the nonin vasive detection of RF magnetic fields, and for mapping the eddy curre nt induced magnetic-field anomalies in nondestructive test evaluation. Since fiber-optic sensing techniques have high immunity to electromag netic interference, the sensor reported here is compatible with integr ation into mapping arrays. (C) 1997 American Institute of Physics.