Fig. 1. Structure diagram of four-light coherent mixing system

Fig. 2. Relationship between frequency and speed of four-light coherent mixing signal

Fig. 3. Structure of space separation type four-light coherent mixing detection

Fig. 4. Signal spectrum output by different detectors at speed of 100 m/s. (a) Detector 1; (b) detector 2; (c) detector 3; (d) detector 4

Fig. 5. Signal spectrum output by different detectors at speed of 1000 m/s. (a) Detector 1; (b) detector 2; (c) detector 3; (d) detector 4

Fig. 6. Signal spectrum output by different detectors at speed of -1000 m/s. (a) Detector 1; (b) detector 2; (c) detector 3; (d) detector 4