Design of high sensitivity gas sensor based on air-core photonic bandgap fiber

An air-core photonic bandgap fiber (PBGF) for gas sensing with high sensitivity is designed. The coupling core modes and surface modes in air-core photonic bandgap fiber cause large propagation losses and will deteriorate the performance of PBGF. There is a relationship between the air-core radius and the surface modes. According to the simulation results, at a special core radius, no surface modes supported by fiber and there is only core modes. By designing Λ=2.63 μm, d=0.94Λ, and R_CORE=1.132Λ, where Λ is the distance between the adjacent air holes, the fiber is single-mode, no surface modes supported with fiber, and more than 90% of the optical power is confined in the core. We consider the operation wavelength λ=1.55 μm that close to the absorption wavelength of acetylene gas. This fiber is suitable to be used to detect acetylene gas and as a sensor node in the optical network protection system of pipelines carrying oil, gas, and other important resources.