The phase modulation depth (PMD) deviation effect substantially constrains the displacement measurement range of fiber-optic sinusoidal frequency modulation interferometer (FO-SFMI), necessitating urgent correction. In this article, the pre-correction of the interfering effects is firstly realized, and the rough and fine two-tiered correction is then adopted to eliminate the PMD deviation effect. Compared with the existing methods, the proposed method offers advantages in terms of accuracy, stability, and ease of implementation. Experiments verified the excellent PMD deviation effect correction results of the proposed method, which supported the measurements with FO-SFMI in the range of 40 to 300 mm, achieving a measurement nonlinearity of 0.6 nm, a resolution better than 1 nm, and measurement stability of 0.58 nm (1σ). These enhancements are significant in expanding the applications of FO-SFMI.

Random-modulation continuous-wave laser ranging is particularly suited to the demands of autonomous driving due to its high data rate and superior signal-to-noise ratio (SNR). However, precision is constrained by modulation and sampling rates. In this paper, we introduce the delay-locked loop (DLL), a data processing method from the global positioning system. Through the analysis of a matched filter and rigorous experimental verification, we have formulated an improved DLL model closely aligned with actual observations. Precision is improved to 4.27 mm at an SNR of 34.17 dB, and performance in imaging experiments is also exceptionally outstanding.

We propose a rapid laser ranging method for compact LiDAR systems. It employs a high signal-to-noise ratio (SNR) coherent detection scheme to minimize the required measurement integration time, while also addressing key challenges encountered by existing rapid coherent ranging methods in compact systems—namely, device fabrication difficulties, the complexity of parallel Doppler frequency shift (DFS) decoupling, and endpoint effect elimination—through low-depth pseudo-random phase modulation (LD-PRPM). Furthermore, it introduces sliding window analysis, which fully harnesses the advantages of continuous-wave measurement and further boosts the ranging rate. In addition, the proposed method is adaptive and resistant to interference. Analysis and experiments validate its effectiveness. In the experiments, the method demonstrated a ranging accuracy of 5 mm, a ranging precision of 2 mm (1σ), and a rapid ranging rate of 10 MHz. These results may offer valuable references for enhancing the temporal or spatial resolution of the compact LiDAR system.

In this letter, we propose and experimentally validate an improved method for high-precision locking of the laser center wavelength based on the absorption spectrum of saturated HCN gas, aiming to enhance the repeatability accuracy of dual-wavelength ranging. By combining with high-precision phase-generated carrier displacement measurement technology, we achieved real-time measurement of the target distance. Our experimental results demonstrate that this method achieves excellent stability for the laser center wavelength, with a wavelength uncertainty of only $1.05\times 10^{-8}$ , a resolution better than 1 nm and a stability of 0.58 nm ( $1\sigma $ ), nanoscale displacement measurement is achieved. These enhancements are significant in expanding the application of sine frequency modulation interferometry.