10-Gb/s homodyne receiver based on costas loop with enhanced dynamic performance

Coherent optical receivers have been widely used in free-space optical communication. We report on a coherent receiver with a homodyne optical phase-locked loop using a Costas loop. Differing from the conventional configuration, the demonstration in this paper with enhanced dynamic performance using an auxiliary acquisition and locking circuitry is able to achieve fast phase locking to signal laser within 10 s at an initial frequency offset as large as +/−12 GHz. The proposed receiver can also compensate for Doppler shifts caused by the relative motion of satellites in real-time. 10-Gb/s Binary Phase Shift Keying (BPSK) data has been demodulated with sensitivity of −39.5 dBm at Bit Error Rate (BER) of 1E-9.