Research on modulating retro-reflector technology of laser communication systems based on acousto-optic modulation

In order to expand the application fields of free space optical communication, a steady and practical communication system of retro-modulation was designed. Based on acousto-optic modulator (AOM) and the reverse link of light, transistor-transistor logic gate level was send to control AOM by using field programmable gate arrays. By using quaternary modulation method combining binary frequency shift keying and binary pulse width modulation, by using the encryption and error correction methods of redundancy checking replacement and improved Hamming code, reverse modulation laser communication indoor was realized. The results show that serial communication rate of the communication system is 115.2kbit/s, high frequency carrier is 1MHz and bit error rate is less than 10-6. Its confidentiality is good. While, it also proves that the maximum carrier wave of laser externally-modulated reverse communication system can reach about 5MHz.