PON technology has become the industry recognized the first choice for the realization of FTTH, this article for you to do an overview of the PON technology, hope that you can more deeply understand the PON.
The PON system consists of OLT, ONU/ONT and optical distribution network (ODN). The so-called "passive" means that ODN is made up of passive optical devices such as passive optical splitter and optical fiber, excluding any active devices. PON technology adopts point to multipoint topology, and downlink and uplink transmit data through TDM and TDMA respectively.
The advantage of PON technology is that it can reduce the occupation of backbone fiber resources, save investment, the network structure is flexible, the expansion ability is strong, the failure rate of the passive optical device is low, it is not easy to be disturbed by the external environment, and the business support ability is strong.
PON technology can be divided into many kinds. The main difference is the difference in the data link layer and the physical layer. There are APON, EPON, GPON and so on. The APON technology has been basically eliminated by the market because of its high cost and low bandwidth. It is commonly used as EPON and GPON.
EPON was put forward by the EFM working group set up in November 2000 and standardized in the IEEE 802.3ah standard. It uses Ethernet as carrier and uplink to send data stream in a burst Ethernet packet, which can provide 1.25Gbit/s transmission rate of up and down symmetry.
EPON adopts Ethernet encapsulation, which is very suitable for carrying IP business, and is in line with the development trend of network IP. Compared with other PON technologies, EPON has the advantage in terms of technology maturity and equipment price, and is considered to be the main technology to realize FTTH.
However, EPON has a defect that it is difficult to host TDM services, including voice or circuit data lines.
The maximum transmission rate of GPON is up to 2.488Gbit/s, the maximum transmission rate is up to 1.244Gbit/s, and the transmission distance is at least 20km, which has the characteristics of high speed and high efficiency transmission. In addition to the traditional ATM, GPON can also support a new GEM (GPON encapsulation) format.
GEM, similar to GFP, can adapt to a variety of user signal formats and any transmission network format, transmitting voice, data and video signals in an inherent format, so that the operators' flexibility in providing business is greatly improved.
GPON can support end-to-end timing and other quasi synchronous services, and can directly support TDM services. It does not require TDM simulation like EPON to improve the quality of TDM transmission.
The OAM mechanism of GPON is perfect, which facilitates the management and maintenance of operators. The GPON series standard made by ITU-T is quite perfect, and it is also quite complex. So far, there are only a few companies in the world to support the standard, and the professional GPON chips have just been launched. This makes the GPON products more expensive and difficult to realize large scale deployment.
At present, the domestic market mainly uses EPON technology, and GPON is used more in foreign markets because of its high technical requirements and high cost. EPON technology is gradually introduced into the security industry because of its mature technology and low price. The PoE switch, with the PON function, has hit a thunder in the video field.