Fiber Optic Gyro (FOG) is a type of sensor that uses the principles of fiber optics to measure the angular velocity of an object. It works by using two beams of light that are sent through a coil of optical fibers. As the object rotates, the difference in the time it takes for the two beams to travel through the fibers allows the FOG to calculate the angular velocity. FOGs are highly accurate and stable, making them a popular choice for applications such as navigation and guidance systems in aircraft, missiles, and spacecraft. They are also resistant to external factors such as temperature and vibration, making them reliable in harsh environments.