Views: 6 Author: Krystal Publish Time: 2022-04-22 Origin: Site
Introduction to PON
1. What is PON
PON (passive optical network) technology (including EPON and GPON) is the development of FTTx (fiber to the home) main implementation techniques, it can save the backbone fiber resources and network level, under the condition of long distance transmission can provide two-way high bandwidth capacity, access to a variety of business, its remote management capabilities and passive optical distribution network structure can significantly reduce operational costs, can support Multiple application scenarios.
2.PON technology development
After years of development, PON has formed a series of concept specifications and product sequences such as APON, BPON, EPON and GPON.
ATM is a cell - based transport protocol. 155Mb/s PON system technical specification, ITU-TG.983 series standard; BPON(BroadbandPON)
The APON standard has since been enhanced to support 622Mb/s transmission rates, with the addition of dynamic bandwidth allocation, protection and other features.
3. Optical fiber access technology
Introduction to EPON
1. What is EPON?
EPON(Ethernet Passive OpticalNetwork) is a broadband access technology that uses the point-to-multipoint network structure, Passive optical fiber transmission mode, high-speed Ethernet platform and TDM(time division multiplexing) time division MAC media access control mode to provide a variety of integrated services.
EPON system adopts WDM technology to realize single fiber bidirectional transmission.
2. Principle of EPON
The following two multiplexing techniques are used to separate signals coming and going from multiple users on the same fiber.
A. Downlink data stream adopts broadcast technology.
B. The upstream data flow adopts TDMA technology.
3. The principle of EPON -- downlink
A. Assign a unique LLID to ONU after successful registration.
B. Add an LLID before the start of each grouping, replacing the last two bytes of the Ethernet leading.
C. When OLT receives data, it compares the LLID registration list. When ONU receives data, it only receives LLID frames or broadcast frames.
4. The principle of EPON -- uplink
A. Compare LLID registration lists before OLT receives data.
B. Each ONU sends data frames in a time slot uniformly allocated by the customer's devices.
C. The allocated time slot compensates the distance difference between onUs and avoids collisions between ONUs.
5. Working process of EPON system
The operation of OLT
A. Generate a timestamp message for system reference time.
B. Assign bandwidth through MPCP frames. 3.
C. Control ONU registration.
The operation of the ONU
A, ONU synchronizes with OLT through the timestamp of the downlink control frame.
B. ONU waits to discover frames
C. ONU performs discovery processing, including ranging, specifying physical ID and bandwidth.
D. ONU waits for authorization. ONU can send data only during authorization time
6. Design of EPON network management system
The EPON network management system consists of four modules: configuration management, performance management, fault management, and security management.
7. Implementation of EPON network management system
A. The realization of EPON network management system includes the realization of management station network management software and agent station software.
B. The management station network management system is a control entity that provides users with a friendly interactive interface and uses SNMP protocol to manage the agent process.
C. The realization of SNMP in agent station mainly includes the realization of agent process software and the design and organization of MIB.
Iii. Introduction of GPON
1. What is GPON?
GPON(Gigabit-capablePon passive Optical network) technology is the latest generation of broadband passive optical integrated access standard based on ITU-TG.984.x (ITU TG.984.x) standard, which has many advantages such as high bandwidth, high efficiency, large coverage, rich user interface, etc. It is regarded by most operators as the ideal technology to realize broadband and integrated transformation of access network services.
2. GPON principle
GPON sends downlink broadcast packets
GPONS uplink TDMA mode
The network topology 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 a means of optical transmission for OLT and ONU. The ODN consists of a passive optical splitter and a passive photosynthetic combiner, which connects THE OLT and ONU.
3.GPON principle - Uplink
A. Uplink data transmission is uniformly controlled by OLT.
B. ONU transmits user data according to the time slot allocated by OLT to avoid data transmission conflicts caused by ONU.
C. ONU inserts uplink data into its own time slot based on the frame allocation, realizing the sharing of uplink channel bandwidth among multiple ONUs.
4. Networking mode of GPON
GPON mainly uses FTTH/O, FTTB+LAN, and FTTB+DSL.
A. FTTH/O is the optical fiber to the home/office. The optical fiber is directly connected to the user ONU after being connected to the overamplifier. Each ONU is used by only one user, which has high bandwidth and cost. Generally, it is targeted at high-end users and commercial users.
B. FTTB+LAN connects different services to the building through optical fiber and connects multiple users through large-capacity ONU (called MDU). Therefore, multiple users share the bandwidth resources of one ONU, resulting in low bandwidth consumption per user and low cost.
C, FTTB+ADSL refers to the optical fiber to the building, and then the business is connected to multiple users in the way of ADSL, which is also a shared ONU for multiple users. The bandwidth, cost and customer base are similar to FTTB+LAN.
Iv. Comparison of GPON and EPON technologies
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 levels, can support upstream and downstream asymmetric rate, GPON in the selection of optical devices more redundancy, so as to reduce the cost.
2. EPON supports only Class A and B ODN levels, while GPON supports Class A, B and C, so GPON can support up to 128 shunt ratios and transmission distances of up to 20km.
3. Compared with GPON standard, EPON standard is based on 802.3 architecture, so its protocol layer is simpler and system implementation is easier.
4. In the process of developing GPON standard, ITU adopts many concepts of APON standard G.983, which is more perfect than EPON standard developed by EFM. Specifying an efficient TC layer mechanism will be a key element in the development of THE GPON standard by ITU.
5. GPON standard stipulates that TC sub-layer can adopt ATM and GFP encapsulation modes, among which GFP encapsulation mode is suitable for carrying IP/PPP and other packet-based high-level protocols.