Sensitivity analysis of FBG sensors for detection of fast temperature changes

In the last few decades, the use of optical fiber is becoming more widespread for communication technologies and sensor applications. In this sense, considering the physical characteristics of the fiber, there are many possibilities for its use in various engineering sectors, not least in the aerospace one. Indeed, using optical fibers to replace traditional electronic devices can provide significant advantages, such as using an extremely lightweight and minimally invasive technology. FBG (Fiber Bragg Grating) sensors are ones of the most widely used instruments for this purpose, and they allow the detection of different physical parameters, including temperature. The aim of the present work is to analyze the performances of FBGs, in particular by evaluating their ability to read short-term thermal transients and comparing it with that of a conventional thermal probe (PT100). More specifically, two optical fibers were used: the first with the FBG sensor area covered by the external coating and the second without this outer layer. All instrumentation was placed in a climatic chamber and subjected to different thermal cycles. Furthermore, the fiber sections with FBGs were not placed directly in contact with the plate on which they were installed. This made it possible to put optical sensors indications that were as independent as possible from the materials on which they were mounted. Tests have shown that optical sensors have an extremely high sensitivity and a much shorter reaction time than the PT100 probe. Data collected by this work allow strategic use of FBG for thermal monitoring using a minimally invasive and extremely accurate technology.