Photonics Dictionary

fiber optic gyroscope

A fiber optic gyroscope (FOG) is a type of gyroscope that uses the interference of light waves to detect changes in orientation or rotation. It operates based on the principle of the Sagnac effect, where a coil of optical fiber is wound in a closed-loop configuration, and light is split into two counter-propagating beams that travel around the coil in opposite directions. When the gyroscope rotates, the phase difference between the counter-propagating beams changes, providing a measure of the rotation rate.

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Key features and characteristics of fiber optic gyroscopes include:

Optical fiber coil: The core component of a fiber optic gyroscope is a coil of optical fiber wound in a closed-loop configuration. The optical fiber coil may be wound on a spool or integrated into a compact, planar structure depending on the specific design and application requirements.

Interferometer: Within the optical fiber coil, the light is split into two counter-propagating beams by a beamsplitter. After traversing the length of the fiber coil in opposite directions, the beams are recombined at the beamsplitter, resulting in interference. Changes in the relative phase of the counter-propagating beams due to rotation are detected as changes in the interference pattern.

Sagnac effect: The Sagnac effect is a physical phenomenon in which the travel time of light beams propagating in opposite directions around a closed-loop path varies depending on the rotation rate of the system. In a fiber optic gyroscope, the rotation-induced phase shift between the counter-propagating beams is proportional to the rotation rate, allowing for accurate measurement of angular velocity.

Detection and signal processing: Changes in the interference pattern caused by rotation are detected by photodetectors and converted into electrical signals. Signal processing electronics analyze these signals to determine the rotation rate and orientation of the gyroscope relative to a reference frame.

Accuracy and sensitivity: Fiber optic gyroscopes offer high accuracy, sensitivity, and stability over a wide range of angular velocities. They are capable of detecting extremely small rotation rates, making them suitable for applications requiring precise navigation, stabilization, and motion sensing.

Compactness and reliability: Fiber optic gyroscopes are compact, lightweight, and robust devices that are resistant to shock, vibration, and environmental factors. They have no moving parts and are less susceptible to wear and mechanical failure compared to traditional mechanical gyroscopes.

Fiber optic gyroscopes find applications in various fields, including aerospace, defense, navigation, robotics, automotive, and oil and gas exploration. They are used for inertial navigation systems (INS), attitude and heading reference systems (AHRS), stabilization of platforms and vehicles, seismic monitoring, and surveying. Due to their high performance, reliability, and versatility, fiber optic gyroscopes are indispensable tools for precise motion sensing and orientation determination in both commercial and military applications.
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