Researchers are studying a number of configurations and mechanisms to detect specific gases and ways to enhance their performances. Evidence is growing that optical fibre gas sensors are superior in a number of ways, and are likely to replace MOS gas sensors in some application areas. Gas sensing detects gas properties, such as physical, molecular, optical, thermodynamic, and dynamic properties. Fiber optic metal oxide (MO) semiconductor sensors have so increased the utility and demand for optical sensors in a variety of military, industrial, and social. Unlike traditional inspection methods, distributed fiber-optic sensing offers continuous, real-time monitoring capabilities, allowing for early detection and response to potential leaks, which is especially crucial in remote or inaccessible locations. These applications can range from environmental monitoring of gases, carbon monoxide detectors and the detection of gas in. Fiber-optic sensors are a versatile and robust class of optical gas sensors, employing optical fibers to transmit and receive light signals. They offer several advantages, including immunity to electromagnetic interference, remote sensing capabilities, and the potential for multiplexing.