Study Of Digital Optical Fiber Communication System Based On CPLD

The core of electronic technology is EDA (Electronic Design Automation) at present. The designers can accomplish the hardware function of system only by using software tool. CPLD (Complex Programmable Logic Device)is one kind of programmable logic devices(PLD), it is characterized by flexible programming, high integration, short cycle of design and development, wide application range, advanced development tool, low cost and high security, it also can realize a large-scale circuit design, therefore, it is widely used in prototype design and production. A point-to-point small digital optical fiber communication system based on CPLD is designed in this paper.The optical fiber communication system can be divided into three parts, namely, optical transmitter, optical fiber, optical receiver. The processed signal from the electronic terminal is used to modulate the light on the optical transmitter, electronic signal can be converted into optical signal in the process. Then the modulated optical signal is coupled to the optical fiber. The optical signal from optical fiber is converted into electronic signal on the optical receiver, then this weak electronic signal is amplified to the enough level and sent to the electronic terminal.At first, the paper confirms the overall design scheme of the ditigal optical fiber communication system. It introduces an overview of the design idea based on CPLD and illustrates the choice of CPLD and how to configure in detail, system on programmable chip is established.Secondly, the software and the hardware design method of the ditigal optical fiber communication system based on CPLD is discussed. According to "top-down" structure in the software part, the whole system is divided into four independent modules: PCM encoder and decoder, time division multiplexing signal source, channel encoder and decoder and digital terminal (bit synchronization, frame synchronization, demultiplexing), the design idea of each module is described amply and the simulation results on MAX+PLUSII are gived. The hardware part includes audio interface circuit, signal amplification circuit, PCM encoding and decoding circuit, periphery circuit of CPLD and power circuit, the chips used in the circuits are introduced, then circuit schematics and experimental waveforms are displayed.Finally, software design files and hardware debugging results of the whole system are presented. Some questions in the software design and hardware debugging are analyzed and the problems in realization of CPLD and the solutions are discussed.The results of software simulation and hardware debugging show that the digital optical fiber communication system can realize basic communication, besides, it is designed correctly and the performance is excellent.