The fibre optic gyroscope (FOG) offers the potential of a low cost, high performance strap down inertial navigational instrument. In this article, the principles of the FOG are reviewed and the factors which limit the performance of the system are discussed. The basic Sagnac interferometer is shown to be susceptible to polarisation effects, optically induced nonlinearities and both spatial and temporal coherence within the optical source and within the passive gyroscope optics. However, with due attention to these phenomena, a high performance instrument is feasible. An assessment of the applications role of this instrument is presented together with some speculations on the required technological developments to produce the instrument.

https://iopscience.iop.org/article/10.1088/0022-3735/16/1/001/pdf

Fibre optic gyroscopes

A fiber gyro with optical heterodyne detection is proposed. The experimental setup has been constructed and tested. Both the frequency difference in the fiber and the path-length difference between counterpropagating waves are eliminated to reduce output drift. An electronic circuit for phase-nulling detection has been constructed, which gives an electronic frequency output in proportion to the rotation rate. Direct frequency modulation of a single-mode laser diode has been adopted to reduce the noise that is due to the backward Rayleigh scattering. A short time resolution of the rotation rate of about 5 deg/h (0.0014 deg/sec) has been achieved with good linearity, for an integration time of 1 sec.

Rotation detection by optical heterodyne fiber gyro with frequency output.

The ring interferometer with a multiturn single-mode optical fiber loop has been investigated for use as a rotation rate sensor utilizing the Sagnac effect. We have proposed an optical system with homodyne detection, in which the phase-difference bias can easily be introduced, and the rotation detection experiment was performed using the preliminary test setup with a He-Ne laser [1].

N. Okuma

Papers

Optical Fiber Laser Gyro: Homodyne and Heterodyne Detections