Rotation sensing with a low-cost simple FOG

Abstract

The fiber optic gyroscope (FOG) is a single axis rotation sensor which is currently employed in many advanced navigation systems. A major contribution to the cost of an FOG is the price of components such as the polarizer, phase modulator and associated detection electronics. As a lower cost realization of the device is of great importance for its wide deployment in many applications, the possibility of rotation rate measurement with moderate accuracy using a simplified FOG configuration is a very interesting issue. A low-cost simplified implementation of the open loop FOG was carried out to investigate its performance in the absence of a polarizer and a phase modulator and observe the extent to which it can usefully detect the rotation rate in the presence of polarization and phase fading. This paper reports on the realization of the simplified FOG configuration and discusses the association of polarization and phase effects to the measurement errors incurred. The results indicate that the error due to the absence of the polarizer and phase modulator can be of the range of only few hundredths of the rotation rate. This is explained by noting that the phase changes in the path affect both perpendicular polarizations approximately similarly leading to ψx being almost equal to ψy and hence the polarizer importance appears when using a phase modulator which affects each polarization differently. Possible practical uses of such a simplified gyroscope configuration are suggested for low accuracy automobile guidance applications.