（1） What is EPON?
EPON (Ethernet Passive Optical Network) is a kind of point-to-multipoint network structure, passive optical fiber transmission method, based on high-speed Ethernet platform and TDM (time division multiplexing) time division MAC media access control method, providing multiple An integrated service broadband access technology.
The EPON system uses WDM technology to realize single-fiber bidirectional transmission.
（2） Principle of EPON
In order to separate the incoming and outgoing signals of multiple user pairs on the same fiber, the following two multiplexing techniques are used.
a. The downstream data stream uses broadcast technology.
b. The upstream data stream adopts TDMA technology.
（3）The principle of EPON-downstream
a. Assign a unique LLID after the ONU is successfully registered.
b. Add an LLID before the start of each packet to replace the last two bytes of the Ethernet preamble.
c. Compare the LLID registration list when the OLT receives data. When the ONU receives data, it only receives frames or broadcast frames that match its own LLID.
（4）Principle of EPON-Uplink
a. Compare the LLID registration list before the OLT receives data.
b. Each ONU sends a data frame in the time slot uniformly allocated by the office equipment.
c. The allocated time slot compensates for the distance gap between the ONUs and avoids collisions between the ONUs.
（5）Working process of EPON system
a. Generate timestamp messages for system reference time.b. Assign bandwidth through MPCP frames. 3. Perform ranging operations.
c. Control ONU registration.
a. The ONU synchronizes with the OLT through the time stamp of the downstream control frame.
b. ONU waits for discovery frame.
c. ONU performs discovery processing, including: ranging, specifying physical ID and bandwidth.
d. ONU waits for authorization, ONU can only send data during authorized time.
（6）Design of EPON network management system
The EPON network management system is divided into four modules according to network management functions: configuration management, performance management, fault management and safety management.
（7）Realization of EPON network management system
a. The realization of EPON network management system includes the realization of management station network management software and the realization of agent station software.
b. The management station network management system is a control entity that provides users with a friendly interactive interface and uses the SNMP protocol to manage the agent process.
c. The realization of SNMP in the agent station mainly includes the realization of agent process software and the design and organization of MIB.