In this paper, a closed-loop signal detection method is proposed to improve the dynamic performance of the resonant integrated optical gyroscope. We firstly establish a closed-loop error model of the angular velocity tracking system with optical nonlinearity and parameter uncertainty based on triangular phase modulation technology. Then, we optimize the loop gains of the signal processing to improve the signal-to-noise ratio of the closed-loop error signal about angular velocity tracking. Secondly, we design a timing sequence control method to effectively eliminate the time-delay of signal processing for optimizing the dynamic performance of the angular velocity tracking system. Finally, a control algorithm is designed to suppress the influence of the optical nonlinearity and parameter uncertainty for improving the dynamic tracking performance of resonant integrated optical gyroscopes. The experimental results demonstrate that the resonant integrated optical gyroscope has a rise time less than 36us, a high frequency response with the bandwidth 13.1kHz and a low scale factor nonlinearity less than 269.2ppm, which verifies the effectiveness of the proposed closed-loop signal detection method for the resonant integrated optical gyroscope.

Wavelength modulation-tunable diode laser absorption spectroscopy (WM-TDLAS) is a critical tool for gas detection. However, noise in second harmonic signals degrades detection performance. This study presents a hybrid denoising algorithm combining Empirical Mode Decomposition (EMD) and wavelet adaptive thresholding to enhance WM-TDLAS performance. The algorithm decomposes raw signals into intrinsic mode functions (IMFs) via EMD, selectively denoises high-frequency IMFs using wavelet thresholding, and reconstructs the signal while preserving spectral features. Simulation and experimental validation using the CH₄ absorption spectrum at 1654 nm demonstrate that the system achieves a threefold improvement in detection precision (0.1181 ppm). Allan variance analysis revealed that the detection capability of the system was significantly enhanced, with the minimum detection limit (MDL) drastically reduced from 2.31 ppb to 0.53 ppb at 230 s integration time. This approach enhances WM-TDLAS performance without hardware modification, offering significant potential for environmental monitoring and industrial safety applications.

Silicon nitride waveguide (Si ₃ N ₄ ), is used as the most important sensitive device because of its excellent high-polarizing characteristics. It has the potential to build the miniaturized, high-precision resonant integrated optical gyroscope (RIOG) in recent years. However, the back-reflection caused by the refractive index difference between the Si ₃ N ₄ waveguide and the pigtail fiber has a non-negligible impact on the accuracy of the gyroscope. In this paper, we propose a method to suppress the back-reflection of the end face of the Si ₃ N ₄ waveguide resonator. We use the Fimmprop module of the simulation software Photon Design to simulate the relationship between the back-reflection coefficient of Si ₃ N ₄ waveguide and different tilt angles. The simulation result shows that when the end face of the Si ₃ N ₄ waveguide is oblique cut by 15°, the back-reflection is the minimum, about -67 dB. The back-reflection obtained through the experiments are about -65 dB, consistent with the simulation result. Together, our data suggested that the back-reflection noise of the Si ₃ N ₄ can be suppressed by the oblique cutting of the end face by 15°. The conclusion can lay a foundation for improving the performance of RIOG based on Si ₃ N ₄ waveguide resonator.