Fiber-optic gyroscopes with enhanced temperature adaptability for geophysical rotational sensing

Fiber-optic gyroscopes, as rotational motion sensors, have emerged as powerful candidates for rotational seismology and Earth rotation observation due to their portability and high sensitivity. However, the stability of fiber-optic gyroscopes is degraded by environmental temperature variation that optical fibers are sensitive to. For the suppression of effects of temperature variation, conventional methods include the device level and post-processing level. However, the former has additional device requirements and higher costs, while the latter has a degradation of compensation for a more general environment. In this abstract, we propose a suppression method at the device level. We find that the effect of thermally induced phase fluctuations is significantly lower in the high-frequency band compared to the low-frequency band. Therefore, by upconverting the operating point of the fiber-optic gyroscope at a high-order harmonic of eigenfrequency, the effect of thermally induced phase fluctuations on the output is greatly suppressed. This method is easy to operate without requiring any additional optical or electrical components. To validate this method, we have conducted a time-varying temperature variation experiment using a portable fiber-optic gyroscope equipped with a 20 km long and 0.3 m diameter fiber-optic coil. The implementation of this upconverted frequency modulation technology resulted in a 32-fold reduction in temperature sensitivity for the fiber-optic gyroscope. The results demonstrate that the proposed technology enhances the temperature adaptability of fiber-optic gyroscopes, which is a critical aspect in practical geophysical applications. At the same time, the self-noise is reduced from 3×10^-8 rad/s/√Hz to 8×10^-9 rad/s/√Hz, further improving its sensitivity to observe geophysical rotation signals. Seismic records will be presented to demonstrate its utility in rotational seismology.