Vibration monitoring based on optical sensing of mechanical nonlinearities in glass suspended waveguides

Vibration monitoring plays a key role in numerous applications, including machinerypredictive maintenance, shock detection, space applications, packaging-integrity monitoring andmining. Here, we investigate mechanical nonlinearities inherently present in suspended glasswaveguides as a means for optically retrieving key vibration pattern information. The principle isto use optical phase changes in a coherent light signal travelling through the suspended glasswaveguide to measure both optical path elongation and stress build-up caused by a given vibrationstate. Due to the intrinsic non-linear mechanical properties of double-clamped beams, we showthat this information not only offers a means for detecting excessive vibrations but also allows foridentifying specific vibration patterns, such as positive or negative chirp, without the need forany additional signal processing. In addition, the manufacturing process based on femtosecondlaser exposure and chemical etching makes this sensing principle not only simple, compact androbust to harsh environments but also scalable to a broad frequency range.