Research And Development Of Burst Mode Optical Transmitter Modules For EPON

In recent years, the communication network has experienced substantial growth. Most backbone networks use fiber and achieve digital and broadband, while little has changed in the access network. The tremendous growth of Internet traffic has accentuated the aggravating lag of access network capacity. The "last mile" still remains the bottleneck between high-capacity Local Area Networks and the backbone network. The conventional techniques are unable to provide enough bandwidth for emerging services such as Video-On-Demand, interactive gaming or two-way video conferencing. Ethernet Passive Optical Networks (EPON), which represent the convergence of low-cost Ethernet equipment and low-cost fiber infrastructure, appear to be the best candidate for the next-generation access network.P2MP structure is used in EPON system. The upstream is transferred in burst mode, while downstream is transferred in continue mode. Because of the particularity of the structure and the transmission in EPON, some key techniques, such as range measure and fast synchronization, are used to ensure an good transmission performance. Burst mode signal is transferred in EPON system. Its characters by which does it know from continue signal is the variety of its range and phase and the appearance of long sequence "0" and long sequence "1". This phenomena is brought by the special structure of EPON system. There is no one kind of facility can generate burst mode signal directly in nowadays market, while we must use the burst mode signal to debug and test the module. So we must simulate the generation of the burst mode signal in the lab.The burst mode optical transmitter is the key part of the EPON system. It is designed to launch the burst mode optical signal in the upstream in the system. The characters of the burst mode optical signal ask the transmitter for some special function such as automatic power control, delay compensation, raise/drop time control and pulse width control. There are many drive chip that have these function. Taking cost and capability into account, we use the MAX3656. Considering of the characters of the 1.25Gbps transmitter in EPON system, we design the circuit andPCB diagram. Some guidelines are tested and some test techniques are introduced. The signal what is transferred in EPON system is generated by the programmable signal generator. This signal is turned into the optical signal and launched by the transmitter. The optical signal has a little distortion. The head and the end of the packet is exact and clear. According as the eye diagram, we find the performance of this transmitter is excellence.