A fiber optic gyroscope (FOG) is a solid-state sensor that measures angular velocity using the Sagnac effect — the phase difference between two light beams traveling in opposite directions around a coil of optical fiber. With no moving parts, a FOG offers high accuracy, long life, and excellent reliability, achieving bias stability far better than MEMS gyroscopes. FOGs are widely used in inertial navigation for aerospace, marine, and defense systems.
What Is a Fiber Optic Gyroscope?
A fiber optic gyroscope (FOG) is an optical gyroscope that uses laser light and optical fiber to measure the angular velocity or rotation angle of an object relative to inertial space. Because it has no high-speed spinning rotor like traditional mechanical gyroscopes, it is a fully solid-state device — which gives it high reliability, a long service life, and strong resistance to shock and vibration.
How Does a Fiber Optic Gyroscope Work?
A FOG works on the Sagnac effect:
- A light source splits a beam into two, sent in opposite directions around a coil of optical fiber.
- When the coil rotates, one beam travels a slightly longer path than the other.
- This creates a measurable phase difference between the two beams.
- The phase difference is proportional to the rotation rate, which the FOG converts into an angular velocity output.
The longer the fiber coil, the higher the sensitivity — which is why high-accuracy FOGs use long fiber coils.
What Are the Advantages of a Fiber Optic Gyroscope?
| Advantage | Description |
|---|---|
| No moving parts | Solid-state, so high reliability and long life |
| High accuracy | Low bias instability and drift, suitable for navigation grade |
| Fast start-up | Near-instant readiness, no spin-up time |
| Wide dynamic range | Measures very low to very high rotation rates |
| Shock & vibration resistant | Robust in harsh environments |
Fiber Optic Gyroscope vs Other Gyroscopes
A FOG sits between MEMS gyroscopes and ring laser gyroscopes (RLG) in the accuracy/cost hierarchy:
- FOG vs MEMS gyro — a FOG is far more accurate and stable than a MEMS gyro, but larger and more expensive. See which is better: fiber optic gyro or MEMS gyro.
- FOG vs Ring Laser Gyro (RLG) — both are optical and highly accurate; FOGs have no moving parts and lower cost, while RLGs can offer higher precision. See the difference between a fiber optic gyro and a ring laser gyro.
What Are Fiber Optic Gyroscopes Used For?
- Aerospace — aircraft and UAV inertial navigation and stabilization
- Defense — missile guidance, targeting, and platform stabilization
- Marine — ship heading and navigation systems
- Surveying & positioning — high-precision angular measurement
For single-axis applications specifically, see what single-axis fiber optic gyroscopes are used for. SkyMEMS produces a family of fiber optic gyroscopes — browse the full fiber optic gyro range.
Frequently Asked Questions
What is a fiber optic gyroscope? A fiber optic gyroscope (FOG) is a solid-state optical sensor that measures angular velocity using the Sagnac effect in a coil of optical fiber, with no moving parts.
How does a fiber optic gyroscope work? It splits light into two beams traveling in opposite directions around a fiber coil. When the coil rotates, a phase difference (the Sagnac effect) develops between them, proportional to the rotation rate.
What are the advantages of a fiber optic gyroscope? No moving parts (high reliability and long life), high accuracy with low drift, fast start-up, wide dynamic range, and strong shock and vibration resistance.
What is the difference between a fiber optic gyroscope and a MEMS gyroscope? A FOG offers much higher accuracy and stability than a MEMS gyroscope but is larger and more expensive; MEMS gyros are compact and low-cost for less demanding applications.
What is a fiber optic gyroscope used for? Aerospace and UAV navigation, missile guidance, marine heading systems, and high-precision surveying.
