GPON Network

What is GPON?

GPON stands for Gigabit passive optical network, it is the latest generation of broadband passive optical integrated access standard based on the ITU-TG.984. x standard, which has many advantages such as high bandwidth, high efficiency, large coverage range, and rich user interfaces. It is regarded by most operators as an ideal technology for achieving broadband and comprehensive transformation of access network services. GPON was first proposed by FSAN in September 2002, and based on this, ITU-T completed the development of ITU-T G.984.1 and G.984.2 in March 2003. Standardization of G.984.3 was completed in February and June 2004. Thus, the standard family of GPONs was ultimately formed.

GPON technology originated from the ATMPON technology standard that gradually formed in 1995, and PON stands for Passive Optical Network in English. The GPON (Gigabit Capable Passive Optical Network) was first proposed by the FSAN organization in September 2002. Based on this, ITU-T completed the development of ITU-T G.984.1 and G.984.2 in March 2003, and the standardization of G.984.3 was completed in February and June 2004. Thus, the standard family of GPONs was ultimately formed. The basic structure of devices based on GPON technology is similar to existing PONs, which are also composed of OLT (optical line terminal) at the local end, ONT/ONU (optical network terminal or referred to as optical network unit) at the user end, ODN (optical distribution network) composed of single-mode fiber (SM fiber) and passive splitter (splitter) connecting the first two devices, and network management system.

GPON Network Features

Unprecedented high bandwidth. The GPON speed can reach 2.5 Gbps, providing sufficient bandwidth to meet the growing demand for high bandwidth in future networks. At the same time, its asymmetric characteristics are more suitable for the broadband data service market.
Full service access guaranteed by QoS. GPON can simultaneously carry ATM cells and/or GEM frames, providing excellent service levels, supporting QoS guarantees, and full service access capabilities. At present, the technology of ATM carrying multiple services such as voice, PDH, Ethernet, etc. is very mature; The technology of using GEM to carry various user businesses has also been widely recognized and has begun to be widely applied and developed. GPON can encapsulate any type and speed of business in its original format and transmit it through PON.
Excellent support for TDM business. TDM services are mapped to GEM frames, and due to the GPON TC frame length of 125 μ s, it can directly support TDM services. TDM services can also be mapped to ATM cells and provide real-time transmission with QoS guarantee.

Simple and efficient adaptive packaging. Using GEM to achieve simple and efficient adaptation encapsulation for multiple business flows. In APON, all multi service flows (voice, data) must undergo protocol conversion and be mapped to ATM cells for transmission. As is well known, a 5-byte AT M header can cause over 10% bandwidth loss compared to 48 bytes of data, especially for long packet data, the packaging process is complex and inefficient. In EPON, although it directly carries Ethernet frames and the implementation process is simple, considering only 8B/10B line encoding already results in 20% bandwidth waste. Coupled with the encapsulation and overhead of Ethernet frames, EPON has a bandwidth utilization rate that is about 30% lower than GPON. Meanwhile, when transmitting TDM services, it is necessary to map them to Ethernet frames through protocol conversion, and there is currently no unified standard for this technology. GPON’s GEM provides a flexible frame structure encapsulation, supporting the encapsulation of fixed and non fixed length frames, achieving universal mapping for multiple services without the need for protocol conversion. The implementation process is simple, the cost is low, and the protocol encapsulation efficiency can reach up to 94%, achieving full utilization of bandwidth resources.
Powerful OAM capabilities. In response to the shortcomings of Ethernet systems in network management and performance monitoring, GPON provides three types of OAM channels from the perspectives of consumer demand and operator operation and maintenance management: embedded OAM channels, PLOAM, and OMCI. They undertake different OAM tasks, forming a C/M Plane (control/management plane) where different information manages their respective OAM functions. GPON also inherits the OAM requirements specified in G.983 and has rich business management and telecommunications level network monitoring capabilities.
The technology is relatively complex and the equipment cost is high. The advantages of GPON, such as carrying multiple services with QoS guarantees and strong OAM capabilities, are largely achieved at the cost of technology and equipment complexity, resulting in higher equipment costs. But with the development and large-scale application of GPON technology, the cost of GPON devices may decrease accordingly.

GPON Network Architecture

Like all PON systems, GPON consists of ONU, OLT, and passive optical distribution network. OLT provides an interface between the network side and the core network for the access network, and connects to various ONUs through ODN. As the core functional device of the PON system, OLT has the functions of centralized bandwidth allocation, control of various ONUs, real-time monitoring, operation and maintenance management of the PON system. ONU provides a user side interface for the access network, providing access to multiple business streams such as voice, data, video, and ODN, and is centrally controlled by OLT. The branch ratio supported by the system is 1:16 1: 32, 1:64, with the development and evolution of optical transceiver modules, the supported branch ratio will reach 1:128. The transmission mechanism of GPON is completely the same as EPON, both using a single fiber bidirectional transmission mechanism. On the same fiber, WDM technology is used to transmit uplink and downlink data at different wavelengths. GPON can use wavelength division multiplexing (WDM) technology to achieve bidirectional signal transmission on the same optical fiber. According to practical needs, corresponding PON protection structures can also be adopted on the basis of traditional tree topology to improve the network’s survivability.

GPON Application in Access Network

GPON can be applied to fiber to home, fiber to building, fiber to roadside, and fiber to junction boxes in access networks.

FTTB for Business

Symmetric broadband services (such as Group Software Content Broadcast、E-mail、 POTS and ISDN dedicated lines (GPON must be able to flexibly provide dedicated line services at different rates) for file exchange, etc.

FTTC and FTTCab

Asymmetric broadband services (such as digital broadcasting services, VOD, IPTV, file downloads, online games, etc.) and symmetric broadband services (such as Content Broadcast, email, file interaction, remote education, remote diagnosis, etc.) are extensions of POTS and ISDNxDSL.

FTTH

Asymmetric broadband services (such as digital broadcasting services, VOD, IP TV, file downloads, etc.)
Symmetric broadband services (such as Content Broadcast, email, file exchange, remote education, remote diagnosis, online gaming, etc.)
POTS and ISDN

GPON Technical Standards

For other PON standards, the GPON standard provides unprecedented high bandwidth, with a downlink rate of up to 2.5Gbit/s, and its asymmetric characteristics are more suitable for the broadband data service market. Providing full service guarantee for QoS, while carrying ATM cells and/or GEM frames, it has excellent capabilities in providing service levels, supporting QoS guarantee, and full service access. When carrying GEM frames, TDM services can be mapped to GEM frames, and using standard 8kHz (125 μ s) frames can directly support TDM services. As a telecommunications level technical standard, GPON also specifies protection mechanisms and complete OAM functions at the access network level.

In the GPON standard, it is explicitly stipulated that the types of services to be supported include data services (Ethernet services, including IP services and MPEG video streams), PSTN services (POTS, ISDN services), dedicated lines (T1, E1, DS3, E3, and ATM services), and video services (digital video). Multiple services in GPON are mapped to ATM cells or GEM frames for transmission, providing corresponding QoS guarantees for various types of services.

Basic Performance Parameters of Gpon Network

GPON provides the following transmission rates:

uplink	downlink
0.15552Gbps	1.24416Gbps
0.62208Gbps	1.24416Gbps
1.24416Gbps	1.24416Gbps
0.15552Gbps	2.48832Gbps
0.62208Gbps	2.48832Gbps
1.24416Gbps	2.48832Gbps
2.48832Gbps	2.48832Gbps

NOTES:

Among them, 1.24416Gbps uplink and 2.48832Gbps downlink are currently the main supported speeds.
It should be noted that unlike EPON, GPON is not completely asynchronous.
Supports a maximum logical distance of 60km
Supports a maximum physical distance of 20km
Supports a maximum distance difference of 20km
The spectral ratio is generally 1:64, and currently mainstream manufacturers can smoothly upgrade the spectral ratio to 1:128

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