Fig. 1. Experimental setup of real-time 8×10 Gb/s PDM-QPSK coherent transmission over a free space optical link

Fig. 2. Optical spectrum of transmitted signal

Fig. 3. Offline DSP architecture. (a) CMA; (b) frequency offset recovery; (c) phase recovery

Fig. 4. Real-time DSP architecture. (a) Core real-time DSP architecture in the FPGA; (b) DSP structure in Dspbuilder

Fig. 5. Pictures. (a) Experimental platform; (b) integrated electrical board; (c) chip planner of DSP architecture in FPGA

Fig. 6. Experimental results. (a) BER performance in a BTB transmission; (b) optical spectrum of received signal and recovered constellation diagram of channel 8

Fig. 7. Real-time DSP results. (a) ADC sampling data; (b) CMA result; (c) frequency offset recovery result; (d) constellation diagram after recovery