Fig. 1. Schematic diagram of optical system for line width measurement

Fig. 2. Demodulation schematic of differential cross multiplication algorithm

Fig. 3. Source signal obtained within 10 s

Fig. 4. Sampled and normalization signals with different sampling windows

Fig. 5. PSD of frequency noise under different sampling window signals

Fig. 6. Sampled and normalization signals of 1.5 μm band single frequency laser at sampling window of 0.5 s

Fig. 7. Sampled and normalization signals of 1.5 μm band single frequency laser at sampling window of 0.05 s

Fig. 8. PSD of frequency noise of 1.5 μm band single frequency laser under different sampling windows

Fig. 9. Variation of linewidth of 1.5 μm band single frequency laser with measurement time in different sampling windows

Fig. 10. Sampled and normalization signals of 2 μm band single-frequency laser with sampling window of 0.5 s

Fig. 11. Sampled and normalization signals of 2 μm band single-frequency laser with sampling window of 0.05 s

Fig. 12. PSD of frequency noise of 2 μm band single frequency laser under different sampling windows

Fig. 13. Variation of linewidth of 2 μm band single frequency laser with measurement time in different sampling windows