On basis of comparing and analyzing the different modes of laser external modulation

this paper focuses on the principle and control methods of Acousto-Optic Modulation（AOM）devices.Then it presents three controllable ones and compares and verifies them respectively.It adopts the TTL level（3.5V/0.2V）control method to modulate and encode the digital signals via FPGA by way of 2FSK and load the modulated signals on to laser light by AOM

which realizes 115.2kbit/s digital communication after free space transmission and the carrier of this laser external modulation communication system reaches about 0.7MHz.