Numerical and analytical modeling of optical fibers for ultrasound detection

The frequency response of optical fibers is investigated in the presented paper. An extended analytical model based on oblique scattering of elastic waves from multilayered cylinder is applied in the investigation of coated and uncoated fibers. Frequency responses are calculated for both types of fibers submerged in water. Typical resonance frequencies of the fibers are identified and visualized with the help of the radial and tangential displacements. The frequency response is also evaluated with a time domain FEM model which shows an excellent agreement with the analytical solution. The numerical model is also extended to polarization maintaining fibers with an inhomogeneous cross-section. It is shown that the inhomogeneity of the cross-section leads to a stress concentration in the center of the fiber and to birefringence for the hydrostatic case.