Sagnactyyppiset

Sagnactyyppiset refer to devices that exploit the Sagnac effect to measure rotation. They use a closed optical path in which light travels in opposite directions; rotation causes a travel-time and phase difference between the counter-propagating beams, yielding an interference signal or beat frequency proportional to angular velocity.

The effect arises from the dependence Δt = 4AΩ/c^2 for a loop of area A, with corresponding phase shift Δφ = (8π A Ω)/(λ c). In practice, the observable is a rotation-dependent frequency or phase, allowing precise sensing of Ω.

The two predominant implementations are ring laser gyroscopes (RLG) and fiber-optic gyroscopes (FOG). RLGs employ a closed laser cavity in a ring; the interference of the counter-propagating beams produces a beat frequency that directly relates to rotation. FOGs use a long fiber coil and a beam splitter to recreate the Sagnac interference, with no moving parts in many designs. Variants include microfabricated and integrated photonic versions.

Sagnactyyppiset devices are used in inertial navigation systems for aircraft, ships, submarines, spacecraft, and handheld devices, where external references are unavailable. Advantages include solid-state robustness and wide dynamic range; RLGs can offer very high bandwidth, while FOGs provide compactness and ruggedness.

Common limitations involve bias drift and scale-factor nonlinearities, temperature sensitivity, mechanical perturbations, and backscattering in the fiber or laser noise. Ongoing research aims to improve stability, reduce size and cost, and enable integration with other sensors.