What is GPON?

GPON (Gigabit Passive Optics Networks, ITU-T G.984) is an evolution of the BPON (Broadband PON) standard. It supports higher rates, enhanced security, and choice of Layer 2 protocol (ATM, GEM, Ethernet).

The GPON standard represents a boost in both the total bandwidth and bandwidth efficiency through the use of larger, variable-length packets. Again, the standards permit several choices of bit rate, but the industry has converged on 2.488 gigabits per second (Gbit/s) of downstream bandwidth, and 1.244 Gbit/s of upstream bandwidth.

GPON Encapsulation Method (GEM) allows very efficient packaging of user traffic, with frame segmentation to allow for higher Quality of Service (QoS) for delay-sensitive traffic such as voice and video communications.

A passive optical network (PON) is a point-to-multipoint, fiber to the premises network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises, typically 32-128.

A PON consists of a central office node, called an optical line terminal (OLT), one or more user nodes, called optical network units (ONUs) or optical network terminals (ONTs), and the fibers and splitters between them, called the optical distribution network (ODN).

The OLT provides the interface between the PON and the backbone network. These typically include:

* Internet Protocol (IP) traffic over Gigabit, 10G, or 100 Mbit/s Ethernet
* standard time division multiplexed (TDM) interfaces such as SONET/SDH or PDH at various rates

An ONT is a single integrated electronics unit that terminates the PON and presents native service interfaces to the user. In apartment buildings, the ONT often separately connects via VDSL or Ethernet to the apartments, at speeds up to 100 megabits.

A PON is a shared network, in that the OLT sends a single stream of downstream traffic that is seen by all ONTs. Each ONT only reads the content of those packets that are addressed to it. Encryption is used to prevent eavesdropping on downstream traffic.