Impact of H2 Gas on Disruptive Birefringence Optical Fibers with Embedded Palladium Particles for Developing Robust Sensors

Optical fiber sensors of hydrogen gas (H-2) are conventionally based on the reaction of a sensitive material deposited on the surface of a fiber. Long-term applications of H-2 monitoring require more robust configurations, less sensitive to the degradations of the sensitive layer. To overcome this issue, we develop disruptive polarisation-maintaining optical fibers composed of a sensitive material (Palladium, Pd) integrated into the silica cladding. We present the development of two Panda-type optical fibers with or without embedded Pd particles. These fibers have been fabricated for evaluating, through the measurement of the birefringence, the contribution of Pd particles on the detection of H-2 gas. We have specially developed a gas chamber for measuring on-line the detection of H-2 during its diffusion into the fiber. Dynamic comparisons between both fibers demonstrate the contribution of Pd particles resulting in a faster response time (of about 20 h for our experimental conditions). These results pave the way to the realization of robust optical fibers with enhanced sensitivity to H-2 gas for developing sensing systems compatible with long-term hydrogen monitoring applications in extreme and harsh environments, such as radioactive waste repositories.