What is XGS-PON?

Dec 13, 2022

What is XGS-PON?

XGS-PON is an updated standard for Passive Optical Networks (PON) that can support higher speed 10 Gbps symmetrical data transfer and is part of the family of standards known as Gigabit-capable PON, or G-PON. G-PON stands for Gigabit PON or 1 Gigabit PON. The “X” in XGS represents the number 10, and the letter “S” stands for symmetrical, XGS-PON = 10 Gigabit Symmetrical PON. An earlier, non-symmetrical 10 Gigabit PON version (XG-PON) was limited to 2.5 Gbps in the upstream direction.

PON technology originated in the 1990’s and has continued to develop through multiple iterations with differing wavelengths, speeds and components emerging as the technology has improved. The common denominator of all fiber optic PON networks remains the unpowered or passive state of the fiber and its splitting or combining components, i.e. no active elements such as optical amplifiers, which would require power, are present in the network. With streaming, high definition, 5G and other emerging technologies continually pushing bandwidth demands, the development of XGS-PON and other standards has proven to be essential.

Simultaneous upstream and downstream transmission over the same fiber is made possible through wavelength division multiplexing (WDM). This technology allows one XGS-PON wavelength or color of light transmission for upstream and another for downstream.

XGS-PON Standard

Standardized PON deployment and operation has been accomplished since initial adoption through the International Telecommunication Union (ITU) standards for the G-PON family and through the Institute of Electrical and Electronics Engineers (IEEE) standards for Ethernet PON or “EPON”. The new XGS-PON standard was released in 2016 and designated as Recommendation ITU-T G.9807.1.

The scope of the new standard defines XGS-PON as 10-Gigabit-capable symmetric passive optical access network for residential, business, mobile backhaul and other applications. To create a comprehensive standard for this symmetrical 10-Gbps evolution of G-PON, elements of the earlier XG-PON physical layer standard were utilized, meaning the same optical transceiver components can be used for either XG or XGS-PON. Protocol layer standards have also been leveraged for the NG-PON2 standard, ITU-T G.989.3.

XGS PON Wavelengths

Although the physical fiber and data formatting conventions for XGS-PON technology remain unchanged from the original G-PON standard, the wavelengths have shifted. XGS-PON operates at a downstream wavelength of 1577 nm and the upstream wavelength of 1270 nm. The main reason for this is to allow multiple PON services to co-exist on the same PON and allow for seamless service upgrade/migration or to allow different service providers to use the same PON or to offer different levels of service (e.g. business verses residential). The wavelengths for XGS-PON differ from other standards such as G-PON and NG-PON2, although the overall PON transmission window of 1260 to 1650 nm is capable of accommodating G-PON, XGS-PON and NG-PON2 standards over the same fiber network simultaneously. As XGS-PON was an update to the XG-PON standard in order to deliver symmetrical capacity, XG and XGS-PON operate at the same wavelengths upstream and downstream, this is the only case where there is reuse of the same wavelengths. Today the majority of operators looking at deploying 10G services opt for XGS-PON.