Fig. 1. The principle block diagram of the coherent detection system^[3]

Fig. 2. The demodulation principle block diagram of the zero difference detection system

Fig. 3. Schematic diagram of heterodyne detection

Fig. 4. Structure diagram of a typical polarization multiplexing system

Fig. 5. Spatial phase relationship between signal light and local oscillator light ^[3]

Fig. 6. Schematic diagram of photoelectric effect

Fig. 7. Structural schematic diagram of EDFA