Fig. 1. The system schematic diagram of FTS-CRDS and CW-CRDS. LC, laser current and temperature controller; FI, fiber isolator; AOM, acousto-optic modulator; APD, avalanche photodiode; DDG, digital delay generator; PZT, piezoelectric transducer; WM, wavelength meter; DAQ, data acquisition system; WM, wavelength meter.FTS-CRDS与CW-CRDS方法的系统原理图 LC, 激光电流和温度控制器; FI, 光纤隔离器; AOM, 声光调制器; APD, 雪崩光电二极管; DDG, 数字延迟发生器; PZT, 压电换能器; DAQ, 数据采集系统; WM, 波长计

Fig. 2. (a) Instantaneous laser current (blue) and instantaneous ring-down time (black), τ(t); (b) wavelength (red) and etalon signal (black). Note that the (a) and (b) figure shows an example with only 4 of 100 the circles. (a) 激光电流(蓝色)及周期性的衰减常数(黑色); (b) 激光电流(蓝色), 激光波长(黑色), 标准具信号(红色); 图中仅展示了100个周期中的4个

Fig. 3. The amplitude spectrum of τ(t) and the periodic noises (~5.5, ~11, ~19 and ~21 Hz). τ(t)的傅里叶幅值谱及周期性噪声(~5.5, ~11, ~19和~21 Hz)

Fig. 4. (a) Ring-down time measured by CW-CRDS, n_d is the number of measurements per current, white points represent out-of-range data; (b) ring-down time measured by FTS-CRDS, n_p is the number of cycles; the x axis represents laser current with the range of 74−86 mA. (a) CW-CRDS测量的衰荡时间, n_d为每个电流点的测量次数, 白色点表示超出色阶范围; (b) FTS-CRDS方法测量的衰荡时间, n_p为所测周期数; 横轴均为激光电流, 为了更清晰地显示谱线中心区域, 这里仅显示了74−86 mA的数据

Fig. 5. The absorption spectra (black dotted line) of CO measured by the two methods and the best fit of Voigt profile (red) and Galatry profile (blue): (a) CW-CRDS; (b) FTS-CRDS; the x and y-axes scales of the residuals obtained by the two methods are the same 在相同条件下, 两种方法测量的CO吸收光谱(黑色虚线)及VP(红线)和GP(蓝线)拟合　(a) CW-CRDS; (b) FTS-CRDS; 两幅图的x轴和y轴的尺度相同

Fig. 6. The measured spectral parameters for various pressures (CW-CRDS (red), FTS-CRDS (black): (a) γ_c (hollow triangle); (b) β (hollow square), γ₂ (hollow triangle). 不同压力下所测得的光谱参数(CW-CRDS所测结果为红色, FTS-CRDS为黑色)　(a) γ_c (空心圆); (b) β (空心方框), γ₂ (空心三角)