We present a study of noise suppression by fusion in fiber-optic gyroscopes based on the source-sharing architecture. A theoretical model is proposed for the detailed analysis of noise mechanism. The importance of the modulation parameters is revealed, and the optimal modulation strategies are given. Through simulations and experiments, we demonstrate that the proposed fusion scheme not only suppresses self-noise including relative intensity noise and thermal phase noise, but also achieves complete elimination of environmental disturbances. Up to 5.8-fold suppression of self-noise and 5.2-fold reduction of bias instability is obtained in the experimental apparatus when compared with the performance before fusion. In the applications of fiber-optic gyroscopes for precision measurement, the proposed schemes effectively suppress the noises at the system level.

For many years, seismological research mainly focuses on translational ground motions due to the lack of appropriate sensors. However, because of the development of devices based on Sagnac effect, measuring rotational waves directly comes available. In this work, a portable three-component broadband rotational seismometer named RotSensor3C based on open loop interferometric fiber optic gyroscope (IFOG) is designed and demonstrated. Laboratory tests and results are illustrated in detail. The self-noise ranging from 0.005 Hz to 125 Hz is about $1.2\times {10}^{-7}{\mathrm{rads}}^{-1}/\sqrt{\mathrm{Hz}}$, and with the harmonics compensation the scale factor variation over $\pm {250}^{\circ }/\mathrm{s}$ is lower than 10 ppm (parts per million). The misalignment matrix method is adopted to revise the output rotation rate. In a special near field experiment using the explosive source, the back-azimuths and phase velocity are estimated by the recorded acceleration and rotation rate. All the results prove the practicability of this new rotational sensor.

Dual-polarization (DP) interferometric fiber optic gyroscope (IFOG) has been studied for over a decade, which has important applications in inertial navigation and rotational seismology. Currently, the Shupe effect is an important factor degrading the accuracy of the DP IFOG. Here, a dual-quadrupolar winding pattern is proposed to compensate for the Shupe effect. The finite-element simulation experiments verify that the phase shifts induced by the Shupe effect in two polarizations are almost reversed and well compensated. Static laboratory test results show that, in this configuration, the angle random walk is reduced 10-fold to 7.1×10−5 °/h, while the bias instability is reduced ninefold to 1.7×10−4 °/h. Moreover, a 3-h temperature variation experiment is carried out. The results show that, compared with the original output, the net rotation rate errors originating from the Shupe effect are effectively compensated and the temperature drift is reduced by 13 times. To summarize, the dual-quadrupolar-wound method is a valid approach to compensate for the Shupe effect, and the temperature adaptability of this DP configuration is greatly enhanced.

We report a design for gravity gradient measurements based on Sagnac interferometry. An structure with two masses is designed to convert the effect of gravity gradients into rotational motion. Sagnac interferometry based on optical fibers is introduced to probe its rotational motion. The systematic effects are analyzed theoretically and validated by the static observation of a experimental apparatus. In a 37-day record, we achieve a noise level of 5 × 10 ^-12 rad s ^-2 Hz ^-1/2 under a room-temperature environment without any vibration isolation and magnetic shielding devices. The corresponding contribution for the gravity gradient measurement is estimated to 1 × 10 ^-2 E Hz ^-1/2 .

Temperature variation degrades the performance of fiber-optic gyroscopes. In terms of a noise mechanism, we report that thermal phase noise contributes to the dominant effect of temperature variation in large fiber-optic gyroscopes when the conventional Shupe effect is basically suppressed. High-order frequency modulation is introduced to reduce the corresponding effect of temperature variation. A time-varying temperature variation experiment has been carried out for verification. Compared with the conventional eigen frequency modulation, the temperature sensitivity is reduced by 32 times, which effectively enhances the temperature adaptability of the fiber-optic gyroscope.

The relative intensity noise (RIN) of the light source is an important noise affecting the performance of portable interferometric fiber optic gyroscopes (IFOGs). In this work, two commonly used RIN suppression methods of IFOG, i.e., time-domain delay structure, and dual-polarization structure, are experimentally compared under the same conditions. On this basis, a composite structure of IFOG is proposed. The experimental results show that the proposed IFOG achieves a better Rin suppression effect, which achieves a sensitivity improvement of up to 6.09 times to 2.3 × 10 ^-8 rad/s/√Hz in an enclosed area of 68 m ² . It has a flat frequency response over a bandwidth of 0.05-100 Hz. The angular random walk and bias instability are improved by 8.65 times and 8.06 times, respectively. These studies provide theoretical and technical support for the development of high-performance IFOG and facilitate its application in more fields.