Magneto-optic field coupling in optical fiber Bragg gratings

A magnetic sensor utilizing direct magneto-optic field coupling in an optical fiber Bragg grating (FBG) is experimentally demonstrated. The FBG’s cladding is etched to expose the propagating evanescent light to the fiber’s surroundings. The etched FBG is surrounded with iron oxide nanoparticles and placed in a magnetic field perpendicular to the fiber. Measurements demonstrate that the λB shifts nonlinearly as a function of magnetic field, i.e. comparable to the magnetization versus magnetic field behavior of the nanoparticles measured by a SQUID magnetometer. This direct manipulation of light with magnetic fields provides an approach to develop future sensors relying on electromagnetic interactions.

► Magneto-optic coupling is accomplished in optical fiber Bragg gratings.
► Fiber’s original silica cladding is replaced with ferric oxide particles.
► Evanescent field interaction results in Bragg wavelength shift with magnetic field.
► Wavelength shift mimics nonlinear magnetization behavior of ferric oxide particles.