This paper proposes a PSK external modulation-based laser communication system.Using a 637 nm all-solid-state laser as a light source and FPGA demoboard as the modem hardware to control the acousto-optic modulator

this system applies the modulated signals to the laser and

using aphotomultiplier tube as a laser receiver via atmospheric channel transmission

improves the traditional PSK demodulation

eliminates phase ambiguity and sets up a complete experiment platform for laser communication systems

realizing a laser communication system with the serial communication rate of 115.2kbit/s and bit error rate of lower than 10-8.