In this study, we investigate coupling of acoustic guided waves from different types of input fibers, through a bonded coupler, to an optical fiber. These acoustic waves can then be detected with conventional fiber Bragg gratings (FBGs). The input waves are measured using a high-resolution 3D laser Doppler vibrometer, and the output waves in the optical fiber are measured using an FBG. We demonstrate that the wave coupling between two waveguides varies with the cross-sectional area and the modulus of elasticity of the fibers.