Basic Concept

Air planes are equipped with laser gyros for navigation. Beside their high precision, they have shown reliability, long term stability, and a long lifetime.
Within this experimental set-up, the basics of the laser gyro are explained and practically studied at the system, which allows full access to all components. The experimental laser gyroscope (gyro) consists of a rugged turntable on which the fibre ring laser is mounted. By means of a motorised rotational stage, the angular motion of the turntable is performed. The ring laser consists of an Erbium Doped Fibre (EDF) and is coiled up onto a drum. The point of rotation lies well within the centre of the drum.

Experimental Set-up

To measure the beat frequency of the CW and CCW mode a so-called heterodyn oupler is used. The ring laser is opened and a fraction of both modes are superimposed. The accessible space for this is formed by two beam telescopes and two thin glass plate which decouple the clockwise (CW) and the counter clockwise (CCW) modes of the ring laser. Using beam splitter cubes, the CCW mode is directed in such a way that the clockwise and counter clockwise travelling modes are superimposed and their interference intensity is detected by means of the InGaAs photo detector. The subsequent photo diode amplifier (PDA) conditions the signal in such a way that it an be counted and displayed.
By counting the beat frequency and multiplying the result with the scale factor of the set-up, the angular speed of the turntable is obtained.
The turntable is driven by a micro step motor which is controlled by an extra required personal computer. Different angular speeds, as well as CW and CCW rotation, are controlled by the provided software. This gives the possibility to verify the linear relation between the beat frequency of both CW and CCW modes and the angular speed. Furthermore, it allows to measure and study of the lock-in effect.