Regarding the difference between EPON and GPON, let's take a look at the comparison between them today.
The application and difference between EPON and GPON
1. PON introduction
1. What is PON
PON (passive optical network) technology (including EPON, GPON) is the main implementation technology for the development of FTTx (fiber-to-the-home), which can save backbone fiber resources and network levels, and can provide bidirectional high-bandwidth capabilities under long-distance transmission conditions. There are various types of access services, and its remote management capabilities and passive optical distribution network structure can greatly reduce operation and maintenance costs, and can support a variety of application scenarios.
2. PON technology development
Since PON appeared, it has been developed for many years, forming a series of concepts, specifications and product sequences such as APON, BPON, EPON, and GPON.
APON (ATMPON)
ATM is a cell-based transport protocol. 155Mb/s PON system technical specification, ITU-TG.983 series of standards;
BPON(BroadbandPON)
The APON standard was later strengthened to support a transmission rate of 622Mb/s, and at the same time added functions such as dynamic bandwidth allocation and protection.
EPON (Ethernet PON)
GPON (Gigabit PON)
3. Optical fiber access technology
2. Introduction of EPON
1. What is EPON?
EPON (Ethernet Passive Optical Network) is a 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 adopts WDM technology to realize single-fiber bidirectional transmission.
2. The principle of EPON
In order to separate the signals in the coming and going directions of multiple user pairs on the same fiber, the following two multiplexing techniques are used.
a. The downlink data stream adopts broadcasting technology.
b. The upstream data stream adopts TDMA technology.
3. The principle of EPON - downlink
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. When the OLT receives data, it compares the LLID registration list. When the ONU receives data, it only receives frames or broadcast frames that conform to its own LLID.
4. The principle of EPON - upstream
a. The OLT compares the LLID registration list before receiving the data.
b. Each ONU sends a data frame in the time slot uniformly allocated by the central equipment.
c. The allocated time slot compensates for the distance difference between the ONUs and avoids the collision between the ONUs.
5. EPON system working process
Operation of OLT
a. Generate a timestamp message for system reference time.
b. Allocate bandwidth through MPCP frame 3. Perform ranging operation.
c. Control ONU registration.
Operation of the ONU
a. The ONU synchronizes with the OLT through the time stamp of the downstream control frame.
b. The ONU waits for the discovery frame
c. The ONU performs discovery processing, including: ranging, specifying physical ID and bandwidth.
d. The ONU waits for authorization, and the ONU can only send data during the authorization time
6. Design of EPON network management system
The EPON network management system is divided into four modules according to the network management functions: configuration management, performance management, fault management and safety management.
7. Implementation of EPON network management system
a. The realization of the EPON network management system includes the realization of the management station network management software and the realization of the agent station software.
b. The network management system of the management station 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.
3. Introduction to GPON
1. What is GPON?
GPON (Gigabit-CapablePON Gigabit Passive Optical Network) technology is the latest generation broadband passive optical integrated access standard based on ITU-TG.984.x (ITU TG.984.x) standard, with high bandwidth, High efficiency, large coverage, rich user interface and many other advantages are regarded by most operators as an ideal technology for realizing broadband and comprehensive transformation of access network services.
2. Principle of GPON
GPON Downlink - Broadcast Transmission
GPONS upstream - TDMA mode
The network topology structure of passive optical fiber transmission mode is mainly composed of OLT (optical line terminal), ODN (optical fiber distribution network), and ONU (optical network unit).
ODN provides optical transmission means for OLT and ONU. It consists of passive optical splitter and passive optical combiner. It is a passive device connecting OLT and ONU.
3. GPON principle - uplink
a. The transmission of uplink data is uniformly controlled by the OLT.
b. The ONU transmits user data according to the time slot allocated by the OLT, so as to avoid data transmission conflicts generated by the ONU.
c. The ONU inserts the uplink data in its own time slot according to the time slot allocation frame, so as to realize the sharing of the uplink channel bandwidth among multiple ONUs.
4. The networking mode of GPON
GPON mainly adopts three kinds of networking methods: FTTH/O, FTTB+LAN and FTTB+DSL.
a. FTTH/O is fiber-to-the-home/office. The optical fiber is directly connected to the user's ONU after passing through the optical splitter. One ONU is only used by one user. The bandwidth is high and the cost is high. Generally, it is aimed at high-end users and commercial users.
b. FTTB+LAN is fiber-to-the-building, and then different services are connected to multiple users through a large-capacity ONU (called MDU), so multiple users share the bandwidth resources of one ONU, each occupying a lower bandwidth and lower cost , generally aimed at low-end residential and low-end commercial users.
c. FTTB+ADSL is fiber-to-the-building, and then uses ADSL to access services to multiple users. It is also that multiple users share one ONU. The bandwidth, cost and customer base are similar to FTTB+LAN.
Four, GPON and EPON technology comparison
According to the different characteristics of GPON and EPON technologies, the following analysis can be made on these two technologies.
1. GPON supports a variety of rate grades, and can support asymmetric rates of upstream and downstream. GPON has greater redundancy in the selection of optical components, thereby reducing costs.
2. EPON only supports ODN levels of Class A and B, while GPON can support Class A, B and C, so GPON can support a split ratio of up to 128 and a transmission distance of up to 20km.
3. Compared with the protocol alone, because the EPON standard is based on the 802.3 architecture, its protocol layering is simpler and the system implementation is easier compared with the GPON standard.
4. ITU has used many concepts of APON standard G.983 in the process of formulating GPON standards, which is more complete than the EPON standard formulated by EFM. Prescribing a high-efficiency TC layer mechanism will become a key for ITU to formulate GPON standards.
5.The GPON standard stipulates that the TC sublayer can adopt two encapsulation modes, ATM and GFP, among which the GFP encapsulation mode is suitable for carrying IP/PPP and other packet-based high-level protocols.
