GPON (Gigabit-Capable PON) technology is the latest generation broadband passive optical integrated access standard based on ITU-TG.984.x standard. It has many advantages such as high bandwidth, high efficiency, large coverage, rich user interface, etc. Most operators regard it as an ideal technology for achieving broadband and integrated transformation of access network services.

GPON was first proposed by the FSAN organization in September 2002. On this basis, ITU-T completed the development of ITU-T G.984.1 and G.984.2 in March 2003, and completed G. in February and June 2004. Standardization of 984.3. Thus, the standard family of GPON is finally formed.

The basic structure of the device based on GPON technology is similar to that of the existing PON. It is also the OLT (optical line terminal) of the central office, the ONT/ONU (the optical network terminal or optical network unit) of the user end, and the first two devices are connected by the single mode. The optical fiber (SM fiber) and the passive splitter (Splitter) are composed of an ODN (Optical Distribution Network) and a network management system.

For other PON standards, the GPON standard provides unprecedented high bandwidth, with a downlink rate of up to 2.5 Gbit/s, and its asymmetric characteristics are more suitable for the broadband data service market. It provides full service guarantee of QoS, and carries ATM cells and/or GEM frames. It has good service level, QoS guarantee and full service access. When carrying GEM frames, TDM services can be mapped into GEM frames, and standard 8 kHz (125 μs) frames can directly support TDM services. As a carrier-class technical standard, GPON also specifies protection mechanisms and complete OAM functions at the access network level.

In the GPON standard, the types of services that need to be supported are clearly defined: data services (Ethernet services, including IP services and MPEG video streams), PSTN services (POTS, ISDN services), and dedicated lines (T1, E1, DS3, E3, and ATM services). ) and video services (digital video). Multi-services in GPON are mapped to ATM cells or GEM frames for transmission, providing corresponding QoS guarantees for various service types.

At present, the main networking modes adopted by GPON are FTTH/O, FTTB+LAN and FTTB+DSL.

1) FTTH/O is fiber to the home / office. After the optical fiber enters the optical splitter, it is directly connected to the user ONU. An ONU is used by only one user. The bandwidth is high and the cost is high. Generally, it is aimed at high-end users and commercial users.

2) FTTB+LAN is a fiber-to-the-building, and then accesses multiple services to multiple users through a large-capacity ONU (called MDU). Therefore, multiple users share the bandwidth resources of one ONU, each occupying lower bandwidth and lower cost. , generally for low-end residential and low-end business users.

3) FTTB+ADSL is fiber-to-the-building, and then accesses multiple users in ADSL mode. It also shares multiple ONUs with multiple users. The bandwidth, cost and customer base are similar to FTTB+LAN.

The maximum downlink rate of GPON is 2.5Gbps, the upper behavior is 1.25Gbps, and the split ratio is 1:64.