Self-noise reduction in a FOG-based rotational seismometer confirmed by Allan variance analysis

Reducing noise in fibre-optic gyroscope (FOG)-based rotational seismometers is crucial in guaranteeing their applicability as future high-precision sensors. This paper presents a practical approach to noise analysis of a designed and manufactured FOG-based three-axis rotational seismometer. The performed measurements show that proper identification of noise sources and subsequent changes to the device’s configuration which addressed these noise issues, visibly improved the Allan deviation plot of the device. In particular, angle random walk was reduced from 100–200 to around 35 nrad/s/√Hz and bias instability – from several dozens down to single nrad/s. These improvements were achieved only by elimination or mitigation of the impact of all noise sources, without changing any optoelectronic components of the constructed device and without applying any additional post-processing methods.