Innovators at NASA Armstrong developed an optical waveguide fiber Bragg grating (FBG) that is sensitive to an external magnetic field. The technology allows direct coupling of the external field to the electromagnetic (EM) wave propagating in the fiber, bypassing the need to first measure strain.
The properties of the waveguide material are directly and incontrovertibly influenced when exposed to an external field. In contrast to other FBG-based methods that detect external fields via a mechanical change (e.g., magnetostriction-induced strain), this innovation uses ferromagnetic nanoparticles to achieve a direct coupling of the external field to the optical behavior of the fiber. Thus, the technology can be used as a sensor to detect and map magnetic fields. Alternately, a known magnetic field can be applied to create a particular optical transmission behavior in the waveguide, thus creating an optical switch or selective filter.
This technology is part of Armstrong’s portfolio of fiber optic sensing technologies (FOSS). The innovation leverages Armstrong’s work in this area, including its patented FBG interrogation system, which allows for a diverse set of engineering measurements in a single compact system. In addition to magnetic field, other measurements include structural shape and buckling modes and external loads, and cryogenic liquid level.