Here, a space-domain active fiber cavity ring-down (FCRD) gas sensing technique was proposed to develop a high-performance gas sensor. Optical Fibre Grating Sensors Grating sensors are classified as follows, fibre Bragg grating (FBG), tilted fibre Bragg grating (TFBG), and long period grating (LPG) [27, 28, 29, 30, 31, 32]. Fiber optic sensors' inherent benefits of lightweight, compact size, and low attenuation were actively leveraged to overcome. Gas sensing detects gas properties, such as physical, molecular, optical, thermodynamic, and dynamic properties. Light-induced acoustic techniques include monitoring the optical and physical properties of the gas.