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A fiber Bragg grating is a longitudinally periodic refractive index modulation in an optical fiber. Reflections from successive periods reinforce near the vacuum wavelength ${\lambda }_B=2n_{\mathrm{eff}}\Lambda$, where $\Lambda$ is the period and $n_{\mathrm{eff}}$ is the guided mode's effective refractive index.

It acts as a wavelength-selective reflector while much off-resonant light continues through the optical fiber. Stretching the fiber changes the period and usually the effective refractive index, moving the reflected peak. This supports strain sensing; temperature also shifts the peak, so a strain measurement needs temperature control or independent compensation.

A researcher whose joint work demonstrated fiber Bragg grating measurements of magnetostriction. The optical gauge records how a specimen’s dimensions change in a pulsed magnetic field. The experiment must resolve the rapid response during the pulse, rather than assuming a slowly varying field and a static length measurement.^[ref]

A researcher whose team used fiber Bragg gratings to measure magnetostriction of small single-crystal specimens. Bonding the fiber sensor to a sample transfers its strain into an optical wavelength shift. The apparatus makes structural responses accessible under short, strong magnetic field pulses and cryogenic conditions.^[ref]

A researcher whose team developed an optical method for measuring magnetostriction in pulsed magnetic fields. A fiber Bragg grating attached to a small specimen changes its reflected wavelength as the specimen strains. Fast optical readout tracks tiny length changes during the short field pulse, including at cryogenic temperatures. The method connects mechanical deformation with the magnetic response of a material without requiring electrical strain readout beside the specimen.^[ref]