Surface treatments to enhance the sensitivity of plastic optical fiber based accelerometers

The paper discusses the possibility to improve the sensitivity of a plastic optical fiber based accelerometer using physical treatments on the polymer surface to modify the light propagation characteristics. The considered accelerometer, having the target of being low-cost and compact, exploits the variation of propagation loss along the fiber induced by the deformations of a miniaturized cantilever on which the fiber is fixed. This simple setup, however, does not exhibit a sufficient sensitivity unless the fiber surface is properly treated in order to enhance the loss dependence with the cantilever bending. Two approaches are compared, namely plasma micro- and nano-texturing and laser localized ablations. Several prototypes of accelerometers have been fabricated using various types of plastic fibers and characterized using a vibration test facility. Preliminary results show that both techniques are effective, although most recommended for different types of applications. In particular, the laser localized ablation has proved to be the most suitable to realize accelerometers for industrial applications, like the monitoring of vibrations due to moving parts of machines.