This presentation provides an overview of optical sensors, including their introduction, working principles, classification, applications, and future trends. Optical sensors are classified as either extrinsic or intrinsic based on whether the light interacts with the measurand inside or outside of the optical fiber. They have a wide range of applications in areas such as temperature, chemical concentration, strain, biomedical, and more. The presentation concludes that optical sensor technology will continue to improve and be an important area of research going forward.