Low-Cost, high sensitivity, signal processing-enhanced fiber Bragg grating sensing system for condition-based maintenance application

This paper presents a low-cost, high sensitivity fiber Bragg grating sensing system specifically designed to measure the amplitude of weak signals at audio frequencies. Low cost is obtained using for the optical part an intensity based interrogation scheme, with time and wavelength divi- sion multiplexing to create a sensor network that minimizes the expense per sensing point. Then, performances are dramatically improved using sequential signal processing techniques, which clear noise inside and outside the sensor, and provide an exceptionally performing spectral estimation. This way, the sensor gains 66 dB of signal-to-noise performance, and is able to measure vibra- tions as low as few picostrains, with a frequency resolution of 0.05 Hz. Example of application to multipoint condition-based maintenance application in industrial machineries is given. In this case, the proposed optical sensor is used to detect very weak signals buried into noise coming from ball bearings and rotating elements that are about to break, and can raise a warning alert well before critical damages occur.