Fiber-based gas sensing is important because it offers several unique advantages compared to traditional gas sensing technologies, such as high sensitivity and accuracy, a compact and lightweight design, remote sensing capabilities, multiplexing, and distributed sensing. We review the recent. Spectroscopic Optical Fibre Sensors Generally, spectroscopic techniques have been applied to fibre-optics sensors and are relatively successful in gas sensing applications. Two major mechanisms underpin these types of sensors. Photographs of the experimental facility and a.