Fibre optic gyroscope

A fiber optic gyroscope contains a coil with a long (up to 5km) wound optical fiber (3). Two light beams travel along the fiber in opposite directions. An optical system with a beam splitter (2) directs the beams on a photodetector (4).

When the attitude rate is zero, the phase shift between the two beams is 180°; they cancel each other and the output photocurrent is minimized.

With the attitude rate oriented along the fiber (around the coil's axis), the original phase shift is changed. This change occurs because of the increase in the light path for one beam and decrease in the path for another beam. As a result, the photodetector's current responds to the increased illumination and becomes larger. (Sagnac effect)

See also

• Gyroscope
• Ring laser gyroscope
• Vibrating structure gyroscope
• Quantum gyroscope

See also: Fibre optic gyroscope, Beam splitter, Gyroscope, Optical fiber, Phase shift, Photocurrent, Photodetector, Ring laser gyroscope, Sagnac effect, Vibrating structure gyroscope