Function-optimized fiber optic sensing for the detection of low hydrogen levels with structured palladium coated pi-shifted fiber Bragg gratings

• Applicant: Professor Dr. Johannes Roths
• Subject Area: Measurement Systems
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 448330062

For robust and highly precise detection of low levels of hydrogen, new methods for optimizing the functions of fibre optic sensor elements will be considered in this research project. Due to the increasing role of hydrogen in the energy sector and the corresponding safety issues, sensitive hydrogen detection techniques will have increasing relevance. Fibre optic sensor solutions provide several advantages. Multiple measurement locations can be integrated into the same sensor fibre due to the wavelength multiplexing capabilities of fibre Bragg gratings (FBGs). The optical signal cables bear no risk for spark ignitions and thus can be installed in potentially explosive environments. However, up to now, no fibre optic sensing schemes have been presented that show sufficiently low detection limits, integrated temperature compensation and sufficiently high robustness for real world applications. The new approach proposed within the frame of this research project consists of structuring both the Bragg grating (thus realizing pi-shifted FBGs) and the palladium coating. With this approach temperature-copmensated hydrogen detection limits of ~400ppm are expected while the cross section and the robustness of the fibre is retained. This is achieved by reducing the spectral linewidths and by sensing the temperature and the hydrogen concentration at exactly the same location, which allows very precise temperature compensation schemes. In addition to that, new transducer materials as Pd/Hf alloys will be investigated. These sensor elements represent a new generation of fibre optic sensors, which have optimized functionality due to dedicated micro structuring.

• DFG Programme: Research Grants
• International Connection: China
• Partner Organisation: National Natural Science Foundation of China
• Cooperation Partner: Professor Dr. Minghong Yang