Fiber specklegram sensors (FSS) for measuring high frequency mechanical perturbations

In this work, a technique for measuring high frequency micro-vibrations by using non holographic fiber specklegram sensor is experimentally demonstrated. In our setup, a laser source emitting at 632nm is coupled to a structure of Singlemode-Multimode-Singlemode fibers which produce a filtering effect that is used as optical transducer. Mechanical perturbations of controlled amplitude and frequency are applied to the Multimode fiber, which is fastened at the ends to induce vibrations. Perturbations higher than 3 KHz and below one micron are perfectly recovered by the system, which additionally, exhibits a linear response. Due to the low cost and the simplicity of the technique, it becomes an interesting method for the implementation of fiber sensors in a wide range of engineering applications.