Due to the absence of moving mechanical parts, dual-comb spectroscopy (DCS) can achieve higher spectral sensitivity and shorter acquisition duration compared with Fourier transform spectroscopy. This paper discusses the basic knowledge, challenges, and latest progress in the specific field of dual-comb spectroscopy. Optical Frequency Comb (OFC) - The Foundation of DCS With the advancement of laser technology, ultrashort pulse lasers have provided a new technique for high-precision spectral measurement. To accurately monitor wavelengths, the optical frequency comb (OFC) was designed. It is a pattern of ultrashort laser pulses with equal spacing in the time domain or a persistent and evenly distributed spectral band with the same spacing. Over the past few decades, dual-comb spectroscopy (DCS) has widely used two types of OFCs with small frequency variations. Differences Between Fourier Transform Spectroscopy (FTS) and DCS Fourier transform spectroscopy (FTS) involves the integration of the wave interference pattern diagram of two fixed-phase light beams from Michelson interference, referred to as the moving arm and the static arm. The DCS process involves two different OFC beams with different repetition intervals, which are used to replace the moving and static arm pulses of coherent beams. Due to the core reason of varying repetition frequencies, the pulses of the two OFCs will "cross each other" in the time domain to generate a connected waveform diagram. Types of DCS Modules DCS can be divided into two categories based on the detection of light changes. The first type of DCS can instantly surpass the pulses of two OFCs, identify samples with balanced output, and only retrieve the intensity output after Fourier transform. Another type of DCS allows one OFC to penetrate the sample as a probe laser and surpass another standard OFC to obtain the amplitude output of the sample and the phase profile after Fourier transform. What Challenges Does DCS Face? In recent years, DCS has attracted much attention due to its ultra-fast scanning speed, significant signal-to-noise ratio (SNR), excellent resolution, and reliability. However, there are still challenges in achieving DCS with high repetition precision for two highly correlated OFCs. The core reason is that carrier pulses are measured in femtoseconds. Slight time spike fluctuations or phase changes between the two OFCs will cause distortion of the interference pattern, which will be difficult to eliminate in future data processing. Applications of DCS in Near-Infrared Absorption Spectroscopy The latest article in the "Chinese Chemical Letters" provides a comprehensive background and overview of the progress in dual-comb spectroscopy. It also mentions the application of DCS in near-infrared absorption spectroscopy. The variable and repeated amplitude maxima of the chemical intrinsic assimilation of groups in the mid-infrared region are involved in the spectral absorption spectroscopy of the near-infrared range. However, due to the limitations of current technical constraints, only DCS of gas particles with good transparency, large absorption points, and small absorption peak widths in the near-infrared spectrum has been studied so far. The rotational-vibrational bands of H13C14N, including absorption bands in the THz range and with an SNR of 120, were monitored using a stable DCS setup, with detectability in the range of 1495 nm to 1620 nm and a periodic increment of 155,000 Hz. Can DCS Be Used in Mid-Infrared Absorption Spectroscopy? According to research, the highest spectra of vibrational assimilation of almost all types of particles can be found in the mid-infrared range, which is approximately 1-2 orders of magnitude larger than that in the near-infrared region. Since high precision is considered more suitable for chemical monitoring, especially gas particle monitoring, several near-infrared DCS technologies have been successfully converted to the mid-infrared range using difference frequency generation (DFG) technology. Ultraviolet Dual-Comb Spectroscopy An article published in "Optics Express" introduces readers to the basic steps taken in developing the first ultraviolet dual-comb spectrometer. In the ultraviolet region, many families of compounds have crowded multi-line spectra. In particular, nitrous oxide, the main component of carbon emissions, and gases of great astrophysical significance, exhibit unique reflection spectra in the ultraviolet range with a large number of absorption cross-sections. Researchers proposed a suitable UV-DCS prototype model based on the latest technology with optimal performance. V-DCS can provide a comparison accuracy of at least 10-9. UV-DCS allows extensive ultra-broadband studies of molecules and atomic vapors in the spectral region, including element-specific valence electron transitions, which often overlap with vibrational resonances. What is Compressed Dual-Comb Spectroscopy? A new study published in "Scientific Reports" reviews compressed dual-comb spectroscopy. Compressed sensing (CS) is a processing method that allows the reconstruction of a signal from a drastically reduced number of points by utilizing the sparsity of the signal. To solve the data volume problem of high-speed, high-bandwidth, and high-resolution dual-comb spectroscopy, researchers designed compressed dual-comb spectroscopy (C-DCS). Quantitative simulations of C-DCS for two molecular substances (N2O and CO) showed that the required data points were reduced by more than half within the allowable mole fraction uncertainty range of 3%. It has been found that CS is particularly beneficial for DCS because it generates a large amount of data with a wide spectral frequency and is multi-spectral, ensuring maximum sparsity and thus effective data compression. In addition, the fast scanning rate of DCS creates high-speed data streams, which may lead to problems in data transmission and storage. In short, dual-comb spectroscopy has great advantages, but research is needed to overcome the problems faced in its rapid commercialization.