Fiber Bragg Grating (FBG) sensors are the most common type of fiber optic sensors. They can be used either as strain gauges or as thermal sensors. They have some characteristics that give advantages with respect to traditional strain gauges and thermal sensors. Fiber optic sensors are immune from electromagnetic interferences. They can be multiplexed: a single optical fiber can carry more than 50 FBG sensors; in this way it is possible to drastically reduce the number of cables on the structure to be monitored. The possibility of using FBG sensors to monitor ground testing of space structures has been investigated. Three FBG sensors have been put on the Galileo GioveB satellite to acquire data during vibration tests, in order to compare the measurements with the ones obtained by traditional sensors, and to determine what technological problems must be solved to make fiber optic sensors competitive. Some problems were highlighted, related to the type of adhesive to use, and the handling of the sensors. The data acquired have been processed using output-only techniques, and the results were compared with the data acquired by traditional sensors. Two arrays of FBG sensor will be used as thermal sensors during the thermal vacuum test of the Galileo GioveB satellite. Each array consists of four FBG multiplexed on the same optical fiber. Each sensor has a thermal sensitivity of about 0.1°C, similar to traditional thermocouple sensors.
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