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Monitoring the vibration of industrial engines is essential for running diagnostics that can detect faults and point out the feasibility of predictive maintenance. Therefore, this paper describes an optical accelerometer based on a fiber Bragg grating to monitor the vibration of the gearbox of an industrial engine prototype. Experimental tests were performed varying the motor’s rotation speed during normal operation. To validate the proposed system, two electronic accelerometers were attached to the motor’s gearbox and bearing. The natural frequency response of the optical accelerometer was simulated and good agreement with the experimental results was obtained (0.83% of error). The proposed sensor was able to correctly identify the operation speeds of 20, 25, 35, 40, 45 and 50 rps with a maximum error of 0.05%. The mean signal-to-noise ratio (SNR) of the optical accelerometer was 64.05% higher than the SNR of one of the electronic solutions. The experimental results show that the vibration signals have different characteristics when measured at the bearings and at the gearbox, indicating the feasibility of multi-signals analysis for fault detection.

Optical fiber sensors based on fiber Bragg gratings (FBGs) are prone to measurement errors if the cross-sensitivity between temperature and strain is not properly considered. This paper describes a self-compensated technique for canceling the undesired influence of temperature in strain measurement. An edge-filter-based interrogator is proposed and the central peaks of two FBGs (sensor and reference) are matched with the positive and negative slopes of a Fabry–Perot interferometer that acts as an optical filter. A tuning process performed by the grey wolf optimizer (GWO) algorithm is required to determine the optimal spectral characteristics of each FBG. The interrogation range is not compromised by the proposed technique, being determined by the spectral characteristics of the optical filter in accordance with the traditional edge-filtering interrogation. Simulations show that, by employing FBGs with optimal characteristics, temperature variations of 30 °C led to an average relative error of 3.4% for strain measurements up to 700μϵ. The proposed technique was experimentally tested under non-ideal conditions: two FBGs with spectral characteristics different from the optimized results were used. The temperature sensibility decreased by 50.8% as compared to a temperature uncompensated interrogation system based on an edge filter. The non-ideal experimental conditions were simulated and the maximum error between theoretical and experimental data was 5.79%, proving that the results from simulation and experimentation are compatible.