Palladium/hafnium-coated pi-FBGs: a path to wavelength-encoded, zero-point-referenced, linearized, and temperature-decoupled hydrogen sensing

This study reports, to best of the author’s knowledge, on the first wavelength-encoded, palladium/hafnium (Pd:Hf)-coated grating hydrogen sensor with full zero-point reference, signal linearization, and temperature/hydrogen decoupling. Decoupling was enabled by a partially coated pi-shifted fiber Bragg grating sensor architecture, linearization by iterative matrix processing, and zero-point referencing by a comprehensive sensor calibration procedure, allowing to resolve 100 ppm (H2) with temperature read-out uncertainties <0.6°C. The findings show a higher hydrogen sensitivity of Pd:Hf compared to Pd:Ni. This study builds a promising path for field deployments.