We demonstrate an arbitrary distance measurement method by chirped pulse spectrally interferometry (CPSI) using femtosecond optical frequency comb (OFC). In this paper, the chirped fiber Bragg grating (CFBG) is used to investigate the mapping relationship between displacement and the center frequency of the chirped spectral interferogram. We overcome the direction ambiguity of dispersive interferometry (DPI) ranging and expand the range of distance measurement to 18 cm. Besides, we achieve a full range of dead-zone free ranging by introducing a variable optical delay line (VODL). And through principles simulation and experiment, it is demonstrated that the measurement accuracy is 12 µm in comparison with an incremental He–Ne laser interferometer and the minimum Allen deviation is 52 nm at an average time of 1.76 ms. Similarly, in the experiment with long-distance of ∼30m, the accuracy reaches 20 µm, and 2.51 µm repeatability is achieved under harsh environment.

There is an increasing demand for high-precision gas absorption spectroscopy in basic research and industrial applications, such as gas tracking and leak warning. In this Letter, a novel, to the best of our knowledge, high-precision and real-time gas detection method is proposed. A femtosecond optical frequency comb is used as the light source, and a broadening pulse containing a range of oscillation frequencies is formed after passing through a dispersive element and a Mach–Zehnder interferometer. Four absorption lines of H¹³C¹⁴N gas cells are measured at five different concentrations within a single pulse period. A single scan detection time of only 5 ns is obtained along with a coherence averaging accuracy of 0.0055 nm. High-precision and ultrafast detection of the gas absorption spectrum is accomplished while overcoming complexities related to the acquisition system and light source that are encountered in existing methods.

Since the dispersive interferometry (DPI) based on optical frequency combs (OFCs) was proposed, it has been widely used in absolute distance measurements with long-distance and high precision. However, it has a serious problem for the traditional DPI based on the mode-locked OFC. The error of measurements caused by using the fast Fourier transform (FFT) algorithm to process signals cannot be overcome, which is due to the non-uniform sampling intervals in the frequency domain of spectrometers. Therefore, in this paper, we propose a new mathematical model with a simple form of OFC to simulate and analyze various properties of the OFC and the principle of DPI. Moreover, we carry out an experimental verification, in which we adopt the Lomb–Scargle algorithm to improve the accuracy of measurements of DPI. The results show that the Lomb–Scargle algorithm can effectively reduce the error caused by the resolution, and the error of absolute distance measurement is less than 12 μm in the distance of 70 m based on the mode-locked OFC.

To address the inherent trade-off between measurement range and precision as well as the limitations posed by ambiguity range in large-scale high-precision distance measurements, in this paper, we propose a dual femtosecond laser time-of-flight (ToF) sensor based on equivalent time-stretching and an FPGA-enabled coarse-fine fusion architecture. By employing a nonlinear asynchronous optical sampling (ACSOPS) strategy and cross-correlation peak extraction, femtosecond pulses delay is mapped from the femtosecond domain to the microsecond electronic domain, achieving a time-stretch ratio exceeding 10⁴. The proposed system integrates dual-comb nonlinear ACSOPS with traditional pulse ToF measurement, reducing data redundancy, alleviating timing jitter-induced errors and enabling sub - micron ranging precision with low - bandwidth detectors. A time-to-digital converter (TDC) core is implemented on the programmable logic (PL) side to perform millisecond-level coarse measurements over kilometer range. Concurrently, a femtosecond-level fine ranging algorithm based on cross-correlation peak phase extraction is executed on the processor system (PS) side. Real-time data fusion across the two domains is achieved via an AXI-Stream bus. And experimental results demonstrate that the proposed sensor achieves a root-mean-square (RMS) precision of less than 6?m over a long range, effectively eliminating ambiguity in distance measurements. The system's high level of integration represents a significant step toward transitioning femtosecond-level ranging technology from laboratory research to industrial applications, providing what we believe to be a novel solution for high-precision distance measurements in dynamic industrial environments.

Absolute ranging based on dual femtosecond lasers employing nonlinear asynchronous optical sampling is characterized by a wide measurement range, high precision, and fast measurement speed. In this work, we present an omnidirectional femtosecond absolute ranging system for high-precision multi-target coordinate measurement in large-scale applications. The system integrates a 2D universal-joint rotary axis with dual femtosecond laser absolute meters, using a standard sphere with 40 nm sphericity as a reflective reference and measurement origin to compensate for geometric errors. The optical probe rotates around the sphere, extending the angular measurement range while suppressing rotary-axis–induced geometric errors. A theoretical model quantifies the influence of geometric errors on measurement accuracy, and experiments validate system performance. The femtosecond laser achieves intrinsic distance precision within 5 µm, and multilateration-based coordinate measurement reaches sub-millimeter accuracy (<0.1 mm). These results demonstrate that the combination of a standard sphere and 2D universal joint effectively eliminates rotary-axis–induced geometric errors, providing a reliable solution for large-scale, high-precision multi-target coordinate measurement in industrial metrology.