How does a fiber optic gyroscope measure angular velocity?
1 Answer
A fiber optic gyroscope (FOG) is a device that measures angular velocity (rotation rate) based on the principles of the Sagnac effect, an optical phenomenon discovered by French physicist Georges Sagnac in 1913. FOGs are commonly used in various applications, including navigation systems, aerospace, and robotics, due to their high accuracy and reliability.
Here's a simplified explanation of how a fiber optic gyroscope works:
Basic setup: A FOG consists of a coil of optical fiber wrapped around a spool or a coil of fiber optic cable. The light source, typically a laser diode, emits a coherent beam of light that is split into two beams. These two beams travel in opposite directions along the length of the coiled fiber.
Sagnac effect: When the FOG is stationary or not rotating, the two beams of light travel the same distance along the coiled fiber in opposite directions. As a result, they recombine at the output detector, and the interference pattern formed by the two beams is either constructive or destructive, leading to no net change in the intensity of the detected light.
Angular velocity: When the FOG experiences rotation around its axis (angular velocity), the path length traveled by the two light beams becomes unequal. The beam traveling against the direction of rotation covers a shorter distance, while the beam traveling with the direction of rotation covers a longer distance.
Phase shift: Due to the path length difference, the two light beams experience a phase shift relative to each other. The phase shift is directly proportional to the angular velocity of the FOG. This phase difference causes constructive or destructive interference patterns when the two beams recombine at the output detector.
Output detection: The interference pattern formed by the recombined beams is detected by a photodetector. The photodetector converts the optical interference into an electrical signal. This signal contains information about the phase difference and, consequently, the angular velocity of the FOG.
Signal processing: The electrical signal from the photodetector is processed to extract the angular velocity information. Signal processing techniques such as analog-to-digital conversion, filtering, and data analysis are used to obtain the precise angular velocity measurement.
By continuously measuring the phase shift between the two beams of light, a fiber optic gyroscope can accurately determine the rate of rotation, allowing it to serve as a highly sensitive and reliable angular velocity sensor.
Here's a simplified explanation of how a fiber optic gyroscope works:
Basic setup: A FOG consists of a coil of optical fiber wrapped around a spool or a coil of fiber optic cable. The light source, typically a laser diode, emits a coherent beam of light that is split into two beams. These two beams travel in opposite directions along the length of the coiled fiber.
Sagnac effect: When the FOG is stationary or not rotating, the two beams of light travel the same distance along the coiled fiber in opposite directions. As a result, they recombine at the output detector, and the interference pattern formed by the two beams is either constructive or destructive, leading to no net change in the intensity of the detected light.
Angular velocity: When the FOG experiences rotation around its axis (angular velocity), the path length traveled by the two light beams becomes unequal. The beam traveling against the direction of rotation covers a shorter distance, while the beam traveling with the direction of rotation covers a longer distance.
Phase shift: Due to the path length difference, the two light beams experience a phase shift relative to each other. The phase shift is directly proportional to the angular velocity of the FOG. This phase difference causes constructive or destructive interference patterns when the two beams recombine at the output detector.
Output detection: The interference pattern formed by the recombined beams is detected by a photodetector. The photodetector converts the optical interference into an electrical signal. This signal contains information about the phase difference and, consequently, the angular velocity of the FOG.
Signal processing: The electrical signal from the photodetector is processed to extract the angular velocity information. Signal processing techniques such as analog-to-digital conversion, filtering, and data analysis are used to obtain the precise angular velocity measurement.
By continuously measuring the phase shift between the two beams of light, a fiber optic gyroscope can accurately determine the rate of rotation, allowing it to serve as a highly sensitive and reliable angular velocity sensor.