The design flexibility of Hollow-Core Photonic Crystal Fibres (HC-PCFs) is a significant feature that allows the fibres to achieve excellent optical properties. Changes in the design parameters of HC-PCFs used for gas sensing can affect their optical and gas flow properties. The aim of this paper is to investigate the performance of three HC-PCFs with different geometries (HC-800-02, HC-1550-02, HC-2000-01) in terms of their optical mode and gas flow performance. The numerical model for the optical mode analysis is presented. The optical performance of three HC-PCFs is examined at different wavelengths in terms of their effective refractive index, mode field diameter, confinement loss and relative sensitivity. The numerical model for gas flow simulations based on Navier-Stokes and gas diffusion equations is also presented. This model is used to examine the gas velocity, relative average concentration, volumetric flow rate and gas filling time for three different HC-PCFs and three different gases. A series of gas sensing experiments based on pulsed continuous-wave modulated photothermal spectroscopy is conducted to validate the gas flow numerical model. A comparison between the three HC-PCFs indicates that the HC-PCF with the smallest size is associated with the lowest confinement loss but the highest gas filling time.

中空光子晶体光纤（HC-PCF）的设计灵活性是一项重要功能，可让光纤实现出色的光学性能。用于气体传感的HC-PCF的设计参数的变化会影响其光学和气体流动特性。本文的目的是研究三种具有不同几何形状的HC-PCF（HC-800-02，HC-1550-02，HC-2000-01）的光学模式和气体流动性能。提出了用于光学模式分析的数值模型。根据其有效折射率，模场直径，限制损耗和相对灵敏度，在不同的波长下检查了三种HC-PCF的光学性能。还提出了基于Navier-Stokes和气体扩散方程的气流模拟数值模型。该模型用于检查三种不同HC-PCF和三种不同气体的气体速度，相对平均浓度，体积流量和气体填充时间。进行了一系列基于脉冲连续波调制光热光谱的气体传感实验，以验证气体流动数值模型。三种HC-PCF的比较表明，具有最小尺寸的HC-PCF与最低的限制损失，最长的气体填充时间有关。