Rao Bing-Jie, Zhang Pan, Li Ming-Kun, Yang Xi-Guang, Yan Lu-Lu, Chen Xin, Zhang Shou-Gang, Zhang Yan-Yan, Jiang Hai-Feng. Multi-branch erbium fiber-based femtosecond optical frequency comb for measurement of cavity ring-down spectroscopyJ. Acta Physica Sinica, 2022, 71(8): 084203. DOI: 10.7498/aps.71.20212162