Selection of wavelength bands for ultra-long open-path dual-comb spectroscopy

Dual-comb spectroscopy (DCS) is one of the most promising technologies for ultra-long open-path multiple greenhouse gas detection. Ultra-long open-path DCS has the potential to realize detection configurations, such as horizontal open-path links over hundreds of kilometers and vertical open-path links between satellites and the ground base. Under these extreme detection conditions, identifying an appropriate wavelength band that ensures both technical feasibility and a reasonable absorbance for target components is critical but currently lacks studies. In this work, we simulate transmission spectra under different detection configurations to identify optimal wavelength bands for CO₂ and CH₄ measurement. The simulation results show that the <styled-content style-type="number">1540</styled-content> nm Watt-level high-power frequency combs developed are suitable for CO₂ measurement in both horizontal and vertical ultra-long detection configurations. The results also suggest that developing high-power fiber amplifiers for combs at <styled-content style-type="number">1630</styled-content> nm and <styled-content style-type="number">1636</styled-content> nm will facilitate CH₄ measurement in horizontal and vertical ultra-long detection configurations, respectively. The amplification at <styled-content style-type="number">1636</styled-content> nm will be a future research focus, as it is expected to enable simultaneous measurements of CH₄, CO₂, and water vapor in the vertical detection configuration.