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. Optical fibre gas sensors are capable of remote sensing, working in various environments, and have the potential to outperform conventional metal oxide semiconductor (MOS) gas sensors. Researchers are studying a number of configurations and mechanisms to detect specific gases and ways to enhance. Gas sensing detects gas properties, such as physical, molecular, optical, thermodynamic, and dynamic properties. Fiber-based gas sensing is important because it offers several unique advantages. Pollution in cities induces harmful effects on human health, which continuously increases the global demand of gas sensors for air quality control and monitoring. Optical gas sensors are a crucial component in a wide range of industrial, environmental, and medical applications, providing accurate and reliable monitoring. This article explores the different types of Fiber Optic Sensors, their working principles, and various applications. We'll delve into Intrinsic, Extrinsic, and Hybrid fiber optic sensors, explaining how they function.