【作者】 黄海波；

【导师】 付微； 艾勇；

【作者基本信息】 武汉大学 ， 通信与信息系统， 2004， 硕士

【摘要】 本课题的主要任务分两大部分：一是设计出基于以太网的激光通信电路系统，包括以太网介质转换电路设计、激光调制驱动电路设计和接收解调电路充计；二是设计出一种实用的误码检测系统，包括基于m序列的信号发生器、位同步电路设计和序列同步／误码检测电路设计。 在基于以太网的激光通信电路设计任务中，充分利用以太网的高速接入技术，采用全功能集成芯片IP113，实现双绞线MLT—3 100M信号到光路4B5B信号的编码，提供标准的PECL电平接口，TP口具有10M／100M自适应功能，时钟恢复功能，自动协商功能，并有全／半双工自动转换，提供各种LED组合显示功能，以直观地显示各种工作状况，如失败、连接、活动、速率和全／半双工等。在调制驱动电路中，采用MAX3263芯片，具备标准的PECL电平接口，可以灵活地调整激光器的预置电流和调制电流，并具备自动功率控制功能。在接收解调电路中，采用MAX3963和MAX3964芯片，设计出一套具有灵敏度极高的前置放大和后级限幅放大接收电路，输出信号也是一种标准的PECL电平，并具有无光报警功能。通过对调制驱动电路和接收解调电路组成的激光通信链路的实验测试，表明所设计的光端机具有良好的信噪比。 在误码检测系统的设计中，采用超大规模电路FPGA，利用FPGA的现场可编程技术，配以单片机的实时控制，从而完成整个系统的设计。首先根据CCITT的建议，产生一个周期为512的特殊帧结构的m序列，并根据用户的要求，具有多种码速变换。在接收端的位同步电路的任务是，从接收到的码元中提取位同步信息——码元时钟，并将这一时钟提供给本地m序列同步模块，以便在本地恢复出与测试序列同步的检验序列。序列比较模块用于比较检验序列和测试序列的一致性。通过比较就能知道经过被测信道传输后测试序列中有多少码元产生了错误。并以此评估被测信道的性能。由于m序列是周期序列，所以测试序列和检验序列的比较必须在周期的同一位置开始进行(即同相)。这也是本地序列同步模块的一项重要功能。完成序列比较后，序列比较模块将实时地把传输的总码元数和误码数传送给单片机。单片机是整个误码分析仪的控制中心，它根据用户的选择来控制各个模块的正常工作。 以太网激光通信电路的设计，将以太网的多业务媒体信息借助激光无线通信技术，超越以太网的地域限制，满足数据通信的需要，探索了激光通信的新的应用领域。在误码检测系统的设计中，超越了传统误码测试仪的收发不能分离，测量频率单一，需要提供时钟，体积大，成本高的缺点，实现了收发独立，测量频率范围宽，自适应提取时钟，体积小，成本低的系统设计。更多还原

【Abstract】 The project is mainly dealt with two parts. The first is to develop the laser communication circuit system based on fast Ethernet. Which is composed of the transform circuit for Ethernet medium, the drive circuit for laser modulation and receive circuit for laser demodulation. The second part is to develop a kind of practical error code detector, including signal generator based on m sequence, the circuit for bit synchronization and sequence synchronization.Under the task of the laser communication circuit design based on Ethernet, fully taking advantage of high rate linking technology of Ethernet, with the entire function integrated chip of IP113, there is to realize the encode from MLT-3 signal within twisted-pair 10/100M to 4B5B signal within optical link, provide with standard PECL level interface and self-adaptive 10/100M rate at TP port, taking on clock generating function and auto negotiation function, processing full duplex and semi duplex; with the characteristic of various LED combination display, it is possible to show many indications, such as failure, link, action, rate, full duplex and semi duplex. In modulation driving circuit, with the chip MAX3263, being the function of APC, there is standard PECL level interface to modulate laser modulation current and preset current neatly. In the receiving demodulation circuit, with the chip MAX3963 and MAX3964, there is high sensible circuit for front amplifier and back limited amplitude, also with the function of giving an alarm when no light. Through the experimental test on integration of modulation circuit and demodulation circuit, it indicates that there is high signal-to-noise ratio in the system.In the design for error code detector, with the Grand Scale Integration FPGA and the field programmable technology, under the real time control of the single chip machine, the whole system is efficiently fulfilled. In according to CCITT agreement, a kind of m sequence with special frame construction and period of 512 is generated. At the receiving end, the task of bit synchronization circuit is to extract clock from receiving data, and provide the clock for the m sequence module, so that detecting sequence synchronized with testing sequence. The sequence synchronization moduleis used to compare testing sequence with detecting sequence. After comparison, some error code will be found in the testing sequence crossing the channel, which is guidance to evaluate the performance of tested channel. After comparison, sequence module will send the overall number and error number of code to the single chip machine to process. The single chip machine is the control center for the whole system; it makes the whole system work normally with the respect of user’s need.In the development of Ethernet and laser communication circuit, multimedia information on Ethernet is transmitted via laser wireless communication technology, regional restriction is break through, need of data communication is needed, and new application scope of laser communication is explored. In the design of error code detector, there are some disadvantages discarded, including no separation between transmitter and receiver, detecting single sequence, clock needed, large bulk and high cost. Some advantages are realized, such as independence transmitter and receiver, wide frequency scope, self-adaptively extracting clock, small bulk and low cost.更多还原