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This paper investigates the use of fibre Bragg grating (FBG) accelerometers for wide band vibration monitoring in wound rotor induction generators. The sensor performance is assessed in a series of experiments on a laboratory test rig comprising a 30kW induction machine operating in healthy conditions and with electrical or mechanical fault. Vibration measurements are processed and analyzed in the frequency domain for fault feature extraction. The fibre optic sensor effectiveness in measurement of wide band fault signatures in the vibration signal is compared with that of a commercial piezoelectric based solution. The potential and limitations of the investigated FBG accelerometer design are evaluated for use in condition monitoring applications.

Fiber optic sensors based on fiber Bragg gratings (FBGs) find potential use in condition monitoring because their spectral properties change according to external environmental and/or physical factors. We propose and demonstrate a technique for interrogating multiple FBG-based sensors based on microwave photonic (MWP) filtering. In particular, we exploit the spectrum-slicing properties of two different FBG Fabry-Perot cavities to implement a double passband MWP filter. Each sensor spectrum results in a unique MWP filter passband. As temperature is applied to a sensor, the corresponding MWP filter passband will shift in frequency; we track such shifts by monitoring the detected power at a fixed radio frequency. We discuss the use of a ratiometric approach for enhancing the sensitivity and the impact of cross-talk from the MWP filter responses in terms of simultaneous multi-sensor operation. Results show that we can monitor local temperatures at two (or multiple) different locations simultaneously and independently using a single measurement system.

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