ITU-T members have achieved first-stage approval (“consent”) of a new international standard for optical access at the rate of 10 Gbit/s both downstream and upstream. The new standard will be particularly beneficial to operators as a cost-effective means of upgrading the capacity of the connections provided to businesses in need of symmetrical service.
Recommendation ITU-T G.9807.1 “10-Gigabit-capable symmetric passive optical network” (XGS-PON) was developed by ITU’s standardization expert group responsible for networks, technologies and infrastructures for transport, access and home, ITU-T Study Group 15.
XGS-PON offers a point-to-multipoint optical access system to support a wide range of broadband and narrowband services to homes and businesses, as well as mobile backhaul and other applications.
XGS-PON reuses existing PON standards to the maximum extent possible and capitalizes on PON development efforts underway in the industry. The physical layer of XGS-PON follows XG-PON (ITU-T G.987.2) and 10GE-PON (IEEE Standard 802.3). The standard fully supports operators’ use of existing 10 Gbit/s symmetric transceiver components. The design of the XGS-PON protocol layer is based on NG-PON2 (ITU-T G.989.3) and XG-PON (ITU-T G.987.3), and its ONU management and control mechanism is specified in ITU-T G.988.
XGS-PON operates on the same optical distribution network (ODN) as XG-PON. The typical distance between the optical line terminal (OLT) and an optical network unit (ONU) is 20 km, and one OLT is capable of supporting up to 128 ONUs. The XGS-PON wavelength plan provides for co-existence with G-PON, XG-PON and NG-PON2. An XGS-PON system is fully backward compatible with XG-PON ONUs, allowing the operation of both XGS-PON and XG-PON ONUs under a single XGS-PON OLT port.
ITU-T’s suite of standards for 10 Gbit/s fibre to the home
The ITU-T family of 10 Gbit/s PON standards now offers both asymmetric and symmetric transmission for broadband services, with XG-PON enabling downstream service at 10 Gbit/s and upstream service at 2.5 Gbit/s, and XGS-PON enabling 10 Gbit/s bi-directional service.
The ITU-T standards underlying optical systems for fibre access networks are developed by experts working under the auspices of Question 2 of ITU-T Study Group 15. These experts continue to work in the interests of enhancing the data rates achieved by fibre access networks. A study of 25 Gbit/s per wavelength over PON has been initiated with the aim of enhancing the capacity of PON systems to beyond 100 Gbit/s.
More information on ITU-T Study Group 15 can be found on the group’s homepage.