The use of a modal domain fiber optic sensor for vibration control of a flexible cantilevered beam is experimentally demonstrated. The sensor utilizes mode-mode interference in a two mode elliptical core fiber. The sensor covers a major portion of the beam, and produces a measurement based on the strain distribution in the beam. A distributed-effect model is developed for the fiber optic sensor, and verified through both static and dynamic tests. This model is incorporated into a active control system employing dynamic output feedback. The control system is shown to add damping to the low order modes of the beam. Numerical simulations are presented which concur with the experimental responses, in both open and closed loop tests.