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设计了一种基于数字信号处理机(DSP)的高速高可靠性水下光通信收发系统,并分析了调制时序和信号处理过程。在收发机中,DSP完成待发送信息的里德-所罗门码编码和接收信息的滤波、门限判决、解调解码,现场可编程门阵列(FPGA)完成编码后信息的脉冲位置调制(PPM)。针对激光脉冲水下传输后脉宽展宽小于100ns,激光重复频率偏离均值小于15%的情况,讨论了不同伽罗华域和PPM信息发送速率的关系;分析了收发机的各环节信号处理速度和各接口通信速度。结果表明,收发系统能够实现全双工的实时通信,通信速率可达73kbit/s,可用于实时传输语音和图像等多媒体信息。最后利用Matlab对激光脉冲在Ⅱ类水质中传输100m后到的激光脉冲形状进行了仿真,同时对FPGA发送的一帧数据的电平时序以及模数转换器(ADC)采样得到的一帧数据的采样序列进行了模拟。设计的收发系统为今后水下光通信系统的设计与实现提供了一定的参考。
A high-speed and high-reliability underwater optical communication transceiver system based on digital signal processor (DSP) is designed and the modulation sequence and signal processing are analyzed. In the transceiver, the DSP completes the filtering, threshold decision, demodulation and decoding of the Reed-Solomon codes and received messages to be sent, and the pulse position modulation (PPM) of the encoded information is completed by a field programmable gate array (FPGA). The relationship between different Galois field and PPM information transmission rate is discussed in the condition that the pulse width broadening is less than 100ns after the laser pulse is transmitted underwater and the laser repetition frequency deviates from the average by less than 15%. The signal processing speed and Each interface communication speed. The result shows that the transceiver system can realize full-duplex real-time communication with a communication rate of 73 kbit / s, which can be used for real-time transmission of multimedia information such as voice and images. Finally, the shape of the laser pulse after the laser pulse is transmitted for 100 m in Class II water quality is simulated by Matlab. At the same time, the level timing of one frame of data sent by FPGA and the one frame of data sampled by ADC Sampling sequence was simulated. The designed transceiver system provides a reference for the design and realization of underwater optical communication system in the future.