Development of a High-Performance Rotational Seismometer Based on the Dual-Channel Fiber Optic Gyroscope

This paper presents the development of a high-performance three-component fiber optic rotation seismometer (FORS) named DC-Rot3C for rotational seismic observation. Its core sensing element is a novel dual-channel interferometric fiber optic gyroscope (IFOG), which differs from conventional minimum configuration. The IFOG in DC-Rot3C is composed of two sensing channels, which can effectively suppress self noise such as relative intensity noise. This paper provides a detailed demonstration and analysis of the optical configuration, demodulation technology, layout construction, and noise suppression mechanisms of the developed DC-Rot3C. Furthermore, the performance of DC-Rot3C is tested, and the experimental results show that, with an effective sensing area of only $246\,\,\mathrm{m^{2}}$, the self-noise remains flat from 0.001 Hz to 100 Hz, reaching a sensitivity of $6.2\times 10^{-9}\;\mathrm{rad/s/\sqrt{Hz}}$. Additionally, the angle random walk (ARW) reaches $4.54\times 10^{-9}\;\mathrm{rad/\sqrt{s}}$, and the bias instability (BI) reaches $2.96\times 10^{-10}\;\mathrm{rad/s}$. Compared with other IFOGs and FORSs, the DC-Rot3C exhibits superior performance with the same sensing area, providing a high-precision tool for seismic observation.