A fiber-optic gyroscope is a device that measures rotational movement of the platform or object it is on through the use of fiber-optic technology. This platform can be anything that moves, including a car, boat, airplane or spacecraft. A fiber-optic gyroscope is most often used for stabilization and navigation.
The only things necessary for building a fiber-optic gyroscope are optical fiber, a source of light, a beam splitter and a detector. First the light source emits a beam of light at preset intervals, which the splitter divides into two separate photons. Then those two beams are sent in opposite directions along the optical fiber.
The length of the optical fiber varies in different gyroscopes. In fact, the largest gyroscopes might have 3.1 miles (5 km) of optical fiber, tightly coiled, although most are much smaller. The detector registers when each photon arrives and calculates the time difference between each.
This use of fiber-optic technology is explained by the Sagnac Effect. When the gyroscope is perfectly still, the two beams of light arrive at the same moment. On the other hand, when the gyroscope rotates or tilts, one photon’s trip is shortened. By measuring the time difference between each photon’s return, the gyroscope can determine exactly which way the platform is rotating and how quickly.
A gyroscope can determine a lot of information about its movement, so it is extremely useful as a stabilizer. A fiber-optic gyroscope could be used to stabilize weapons, such as a rotating gun atop a moving tank. In large ships, it is often used to stabilize the satellite antenna so that ships maintain radio communication, even during rough seas.
Another purpose of a fiber-optic gyroscope is navigation. When a global positioning system (GPS) and a fiber-optic gyroscope are combined, the resulting device is known as an inertial navigation system (INS). An INS determines the position of the platform, its velocity, and its orientation. Everything from cars and monorails to boats and airplanes can benefit. Even some spacecraft and satellites carry a gyroscope for precise navigation.
Compared to other types of gyroscopes, the fiber-optic gyroscope is smaller, lighter and more durable. It consists primarily of very lightweight optical fiber; mechanical gyroscopes have several metal pieces mounted on a stand. A fiber-optic version lasts longer than both mechanical and gas-bearing gyroscopes because it has no spinning parts. The fiber-optic type of gyroscope also is very precise because it is able to detect changes as small as one degree per hour.