Spectral Response of an Embedded Fiber Bragg Grating to an Arbitrary Non-Axial Mechanical Impact

In most cases, the properties of fiber Bragg gratings (FBGs) are considered under axial tension or compression. The effects caused by induced anisotropy of the refractive index in FBGs under the action of a transverse load are also known. However, the change in the radiation spectrum reflected from FBGs under the influence of a load acting at an arbitrary angle to the FBG axis on the grating embedded in the elements of the mechanical system has not been studied in sufficient detail. This paper theoretically and experimentally investigated the change in the resonant wavelength of FBGs attached to a disk under the action of a compressive force acting at an arbitrary angle to the FBG axis. The FBG deformation in the static loading mode is theoretically estimated and compared with the experiment. The angle between the direction of the force applied and the FBG axis is determined at which the compression deformation turns into a tensile deformation is determined. It is shown that there is a good agreement between the theoretical and experimental data. It is established that the studied effects for the static load mode also occur under pulsed mechanical load, but with some specifics. The effects described make it possible to more accurately calculate the response of an embedded FBG to mechanical impact.