Funktionsoptimierte faseroptische Sensorik für die Detektion von geringen Wasserstoffkonzentrationen mittels strukturierter Palladiumbeschichtung von pi-verschobenen Faser-Bragg-Gittern

This project examines new methods for function optimisation of fibre optic sensor elements for the robust and highly precise detection of low hydrogen concentrations. Given the increasing importance of hydrogen in energy technology, great significance is now being attached to the monitoring of low hydrogen concentrations as part of the necessary safety technology. Here, fibre optic solutions based on fibre Bragg gratings (FBG) offer particular advantages, due to their multiplexing capability, i.e. the ability to integrate many measurement points into a single sensing fibre, and the potential-free signal lines, i.e., that there is no risk of spark formation caused by the signal lines in potentially explosive areas. However, at the same time, it has not yet been possible to achieve a sufficiently low detection limit, a multiplexing capability, a temperature compensation or a robustness of the sensor elements that is sufficient for real-world applications. The proposed research project will first generate multiplexing-capable sensor elements through targeted structuring measures of the FBG (generation of pi-shifted FBG) and of the palladium coating surrounding the sensing fibres, which would lead us to expect a temperature-compensated detection limit for hydrogen in the area of 400 ppm and at which the cross-section and the high robustness of the optical fibre remains. This is to be achieved through the reduction of spectral line widths and through the fact that the structures permit a simultaneous recording of temperature and the hydrogen concentration at precisely the same spot, and thus a correspondingly accurate temperature compensation. Furthermore, new coating materials, such as Pd/Hf alloys, will be examined. These sensor elements represent a new generation of fibre optic sensors, which feature optimised functions thanks to a targeted microstructuring. 

• Photonik