Methane sensing using multiple-coupling gaps in hollow-core photonic bandgap fibers

Gas detection and gas sensing based on hollow core photonic bandgap fiber (HC-PBF) is a very promising technique due to the long interaction light-gas lengths that are achievable. However, long path-lengths also imply higher gas filling times of the hollow fiber and higher response times of the detection systems what can constitute a serious practical inconvenience. In this paper, the high sensitivity is maintained but the sensor response time is reduced by using multiplecoupling fiber gaps. The results and conclusions extracted from a systematic experimental study (comparing the spectra and filling time of different HC-PBF lengths and different number of coupling gaps) are presented and discussed. Finally, the maximum number of gaps allowed in the system is modelled.