Multi-point hydrogen detection using SPR-based hetero-core structured hydrogen tip sensors and time domain interrogating system by PNCR

In this paper, the multi-point hydrogen detection system has been presented using the hetero-core optical fiber hydrogen tip sensor based on surface plasmon resonance (SPR) and time domain interrogating system based on Pseudorandom Noise code correlation reflectometry (PNCR) This method makes use of the correlation between a launched pseudorandom noise code signal and its reflection, can obtain a high signal to noise ration. A hetero-core optical fiber SPR hydrogen tip sensor consists of multilayer films of 25 nm Au/60 nm Ta₂O₅/5 nm Pd, coated onto a cylindrical cladding surface. The SPR resonant wavelength is shifted 17 nm for 4% hydrogen concentration in nitrogen. In addition, multi-point hydrogen detection is demonstrated using two SPR hydrogen tip sensors. All sensors have successfully detected the hydrogen concentration with real-time responses and sufficient sensitivities.