Modeling of transverse loading effect on Bragg grating signals

Fiber Bragg gratings (FBGs) can provide extremely sensitive strain measurements for various materials and structures. The main functionality of the Bragg grating is along the fiber's main axis, where changes in the grating's spacing can be converted into strain measurements. Previous work from a number of researchers has identified bifurcation and broadening of the Bragg signal under transverse loading. The work presented in this paper highlights efforts to relate transverse loading to changes in index of refraction in the fiber core cross section, and then ultimately to predicted changes in Bragg signals. The modeling work completed provides a useful tool in predicting effects on FBGs of potential transverse loading scenarios, whether these effects are undesirable, or sought after. Analytical and numerical analyses are presented as well as a background of interest in loading effects and birefringence with respect to Bragg grating applications.