Realization of Low Confinement Loss Acetylene Gas Sensor by Using Hollow-core Photonic Bandgap Fiber 

Abstract A hollow-core photonic bandgap fiber (HC-PBF) with high relative sensitivity and low confinement loss was designed. Some destructive circumstance such as propagation losses and mode interference can disrupt performance of the PBF. By considering optimum size of the hollow-core radius, we were able to improve confinement loss and the relative sensitivity. By optimization of the shape and size of the closest row of air holes to the hollow core, the quality of the mode distribution in the hollow-core was well improved. Simulation results confirm that, at an optimal and reasonable core radius, the relative sensitivity and confinement loss of the proposed gas sensor were improved to 96.5% and 0.11 dB/m, respectively. In addition, in order to better matching of optical power between single mode fiber (SMF) and HC-PBF, we could reduce the destructive effects of optical mode mismatch, by mode interference suppression. Furthermore, by optimization of fiber structural specifications such as air filling fraction and lattice constant, the PBF was changed to a single-mode waveguide. Considering the operation wavelength 1530 nm which is very close to the acetylene gas absorption wavelength, this fiber is appropriate to be a high sensitivity gas sensor to detect absorbing gases in the middle infrared range.