1. What is PON
A passive optical network (PON) is a system that brings optical fiber cabling and signals all or most of the way to the end user. Depending on where the PON terminates, the system can be described as fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB), or fiber-to-the-home (FTTH).
Downstream signal coming from the central office is broadcast to each customer premises sharing a fiber. Encryption is used to prevent eavesdropping. Upstream signals are combined using a multiple-access protocol, usually time division multiple access (TDMA).
A PON consists of an optical line terminal (OLT) at the service provider’s central office (hub) and a number of optical network units (ONUs) orOptical Network Terminals (ONTs), near end users.
FTTH has been in the process of 14 years since its promotion in 2003. Since its launch in 2013, Broadband China has gone through another four years. FTTH has developed from the dream of optical communication people to a reality, and has become an indispensable infrastructure for people to work, study and live.
FTTH is the abbreviation of fiber to the home, so we named it as FTTH. Specifically, FTTH refers to the installation of ONUs on home users or enterprise users, and is the closest optical access network application type to users in the optical access family, except for FTTD ( fiber to the desktop ). An important technical feature of FTTH is that it not only provides more bandwidth, but also improves the transparency of the network to data formats, rates, wavelengths and protocols, relaxes the requirements for environmental conditions and power supply, and simplifies maintenance and installation. Speaking of FTTH, you first have to talk about fiber access. Fiber access means that the central office and the user are completely between the fiber as the transmission medium. Optical access can be divided into active optical access and passive optical access. The main technology of optical user network is optical transmission technology.
At present, the multiplexing technology of optical fiber transmission develops quite fast, and most of them are in practical use. According to the depth of fiber users, can be divided into FTTC, FTTZ, FTTO, FTTF, FTTH and so on.
ONU consists of active Optical Network Unit and passive Optical Network Unit.It has two functions: selective reception of the broadcast sent by OLT, and receiving response to OLT if the data is needed;The Ethernet data that the user needs to send is collected and cached, and the cached data is sent to the OLT side according to the assigned send window.
4. What is the difference between ONU and ONT
ONU and ONT are both users’ devices, and there is no difference in essence.But ONT means optical network terminal used by end users.ONU means optical network unit, and there may be other networks between it and the end users.You could also say that ONT is part of the ONU.
5. What is the difference difference between EPON and GPON
1.GPON was defined by ITU-TG.984 and EPON was defined by IEEE802.3ah.
2. The rate is different EPON provides a fixed uplink and downlink rate of 1.25Gbps, and Gpon supports uplink and downlink asymmetric rates of 2.5Gbps or 1.25Gbps and uplink rates of 1.25Gbps
3. The splitting ratio is different GPON supports a maximum splitting ratio of 1:128 EPON supports a maximum splitting ratio of 1:64
6. How to manage ONU
There are 4 management methods of ONU:
1. Web Manahement
2. CLI Management
3. OAM/OMCI Management
4. TR069/SNMP
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