4 Gbps digital coherent free space laser communication system based on modulating retro-reflector

Free-space optical communication (FSO) based modulating retro-reflector (MRR) is propitious to the laser link between small load and ground station because of its advantage such as lightweight, fast pointing. And high sensitivity coherent optical communication can be achieved by digital algorithms. So a MRR free-space optical communication based on digital signal processing technology is simulated and experimentally demonstrated. A FSO model is established by optisystem software, and the simulation result shows that the proposed system is correct. It can be found that the BER of 10^-6 can be obtained when communication distance is about 150km, the transmitter power is 37dBm. Then the proposed system is established in our experiment, and the BER is measured at 3.8 × 10^-8, when a receiver power is -40dBm and the communication distance is about 3m. In our experimental result, receiving sensitivity can be improved about 4dB by EDFA. In conclusion, MRR free-space optical communication based on digital signal processing is experimentally verified, the system may be useful in lightweight wireless laser load in short communication distance.