ZTE has completed a commercial trial with China Telecom intended to show how the Chinese operator can combine different legacy technologies with next-generation 10Gb/s systems on its optical access network.
The trial of ZTE’s Combo passive optical network (PON) solution took place in two local networks in Changzhou and Yancheng, in east China’s Jiangsu province. The trial was undertaken jointly with China Telecom’s Jiangsu branch and the China Telecom Beijing Research Institute.
China Telecom is looking to migrate its existing fibre-to-the-home (FTTH) networks to 10G PON to deliver gigabit broadband services to premises in China – the largest FTTH market in the world (see Optical upgrades in China will resonate worldwide).
But first China Telecom had to resolve a compatibility issue between 10G PON and the existing Ethernet PON (EPON) and GPON central office equipment. Due to the native feature that allows 10G EPON and EPON terminals to be combined under the PON port, 10G EPON has taken the lead in large-scale network upgrades.
However, as a 10G GPON port only supports 10G GPON ONUs and does not support GPON ONUs, the coexistence of 10G GPON and GPON requires more than one wavelength. Traditionally, an external multiplexer is used to combine wavelengths, and the operator must plan, construct and maintain both 10G GPON and GPON equipment and cards. This requires a greater footprint of racks and equipment rooms, bringing an additional 1.5dB insertion loss. The existing optical distribution network (ODN) requires an additional optical power budget of approximately 3dB, which limits its applications.
In comparison to the traditional approach, ZTE says its Combo PON solution is superior because it does not require additional space, does not incur insertion loss or ODN transformation, and supports flexible access and compatibility of 10G PON ONUs as well as GPON ONUs.
The commercial trial used the in-service optical line terminations (OLTs) with the new Combo PON cards to connect XG-PON optical network units (ONUs) and GPON ONUs under the same Combo PON port over the existing optical distribution network. The GPON and XG-PON signals are processed in different MAC chips inside the optical module on the card.
ZTE’s Combo PON cards inherits the system and flow of the carrier’s existing element management system (EMS), operations support systems (OSS) and resource management system, and makes minor alterations to the attributes, as well as performance statistics and alarms for the newly-added Combo PON cards, the company explained.
The existing GPON ONUs are migrated under the Combo PON port, and inherit the existing integrated terminal management system (ITMS) flow to implement automatic distribution and provision of FTTH services, achieving interoperability with the GPON ONTs from multiple vendors – something that has typically been hard to achieve.
The success of the commercial trial indicates that ZTE’s Combo PON solution is ready to move from the lab research stage to the application stage – a solid step for ZTE and China Telecom in commercialising the Combo PON solution. The product was unveiled in February 2016.
Before the upgrade can be rolled out more widely, China Telecom also needs to consider how to optimise the deployment processes to ensure a smooth network migration, and work out how to replace the massive number of ONUs currently in user premises, according to ZTE.