Abstract: A method is described using optical fiber technology to measure the vibration characteristics of long slender structures subjected to dynamic disturbances imposed by water or wind generated loads. The method is based on making bending strain measurements at selected locations along the length of long slender structures such as marine risers or large ropes using fiber optics technology including Optical Time Domain Reflectometry and Bragg diffraction gratings. Engineering interpretation of information obtained from bending strains determines the vibration characteristics including frequency, amplitude, and wave length. Maximum bending strain measurements assess pending structural damage. One application is measurement of vortex induced vibrations (VIV) response of marine risers.