基于声光调制的逆向调制光通信系统研究

摘要

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.%为了扩展自由空间光通信的应用领域，设计了一套稳定性好、实用性较强的逆向调制光通信系统。采用一种基于声光调制器、逆向光链路等核心元件的实验方法，利用现场可编程门阵列发出晶体管－晶体管逻辑门电平对声光调制器进行控制，采用二进制频移键控与二进制脉宽调制调制相结合的四进制调制方法，同时使用冗余校验置换、改进的汉明码等加密纠错方式，实现了室内逆向调制激光通信。结果表明，该通信系统的串口通信速率可达115．2kbit／s、高频载波达1MHz、且保密性良好、误比特率低于10－6，同时证明了激光外调制逆向通信系统载波最高可达到5MHz左右。