Fig. 1. Micro-structured FBG. (a) Cross spiral micro-structured FBG; (b) single spiral micro-structured FBG

Fig. 2. Hydrogen sensor probe of micro-structured FBG. (a) Schematic diagram; (b) sample diagram; (c) fiber surface morphology after coating

Fig. 3. XRD test diagram of nanorod WO₃

Fig. 4. FE-SEM diagram of nanorod WO₃. (a) Pure WO₃; (b) Pt-WO₃

Fig. 5. Performance of smaples. (a) Sample response curve; (b) sample low concentration response; (c) comparison of sample drift

Fig. 6. Single cycle hydrogen response for all samples. (a) H₂ concentration is 1.08%; (b) H₂ concentration is 0.2%