China Unicom and FiberHome Built First C+L Band 400G Test Network

A few days ago, according to the overall arrangement of China Unicom’s 400G test network, under the planning guidance of the Network Department of China Unicom Group and China Unicom Research Institute, Guangdong Unicom and FiberHome Communications built the first C+L band 400G test network, and based on this network, they completed the verification of key projects such as business functions, performance, OMSP protection switching, and smooth upgrade of C+L system, and successfully passed the acceptance. The completion of this experimental network marks a crucial step forward for 400G from laboratory testing to mature commercial use in the current network.
With the implementation of the national strategic project of “counting from east to west”, the digital economy empowers thousands of industries. China Unicom has released the “Action Plan for China Unicom’s New Digital Information Infrastructure”, actively building four boutique networks: 5G boutique network, gigabit broadband boutique network, government enterprise boutique network, and computing power boutique network. The all-optical base is a key element supporting the construction of these four boutique networks, aiming to achieve high-speed and direct computing power transmission, ultra large bandwidth, flexible scheduling, and leading time delay through the all-optical transmission base, Therefore, conducting 400G experimental network testing in various scenarios is particularly important.
This test was built in the Pearl River Delta region 96 × The 400G ROADM network covers three cities, Guangzhou, Shenzhen, and Dongguan. It adopts industry-leading optical transmission technology and equipment such as single wave 400G, constellation probability shaping (PCS) 16QAM modulation code (91.6G and 107G baud rates), C48+L48 extended band, pure EDFA amplification technology, and supports functions such as 100/400G multi rate business mixed transmission, C+L smooth upgrade, and online OTDR monitoring. The project verification content and system indicators meet expectations.

The main features of the system are presented from three aspects:
System capacity: The optical layer adopts a single wave 400G board and utilizes existing network G.652. D optical fiber, which can support up to 96 waves and provide a super large system capacity of 38.4T. This is the maximum transmission capacity at the industry’s experimental network level, providing large particle flow interconnection between four core key cities, and creating a high-speed and low latency all optical interconnection base.
System performance: Using EDFA amplification technology with low engineering cost and high safety factor, the system’s OSNR and other testing indicators have met expectations, indicating that the PCS 16QAM modulation code type can meet the transmission requirements between provincial trunk lines and urban core nodes (the 107G baud rate system has better OSNR indicators).
Smooth upgrade: the existing trunk transmission network of operators is dominated by 100/200G. How to smoothly upgrade to 400G in the future is an urgent issue. At the same time, the SRS effect of optical fiber will make the optical power transfer from C to L when C band is extended to C+L band, leading to system performance degradation; Through this test, FiberHome Communications has provided corresponding solutions that can achieve lossless business cutovers and smooth upgrades.
Wang Guangquan, Chief Engineer of China Unicom Research Institute, stated that the application and commercial deployment of 400G technology needs to take into account the actual network conditions of operators, without changing the transmission network architecture, especially the settings of optical terminals and switching nodes. It is necessary to try not to change the type of optical cables in the current network, do not change the settings of existing computer rooms, optical amplifiers, and relay stations, and do not change operation and maintenance habits, in order to minimize the additional costs brought about by system upgrades as much as possible. This test utilizes all existing computer rooms, power supplies, and optical cables, inheriting traditional operation and maintenance habits, maximizing the protection of existing investments by operators without additional maintenance costs, and directly increasing the single wave rate from 100G to 400G. It not only improves system capacity but also reduces single bit transmission power consumption, which is an important component of building a solid all optical base.
Over the past year, Guangdong Unicom has actively implemented the strategy of building a strong network, accelerated the construction of new information infrastructure, and continued to promote the integration strategy of optical networks in the Bay Area. The successful pilot of 400G has greatly increased the single wave rate and spectral band, greatly expanding the carrying space of the all-optical ultra high speed and low delay network in the Bay Area, enhancing the comprehensive carrying capacity of the Bay Area optical network, and taking the network quality to a new level, supporting the construction and development of the digital economy in the Guangdong Hong Kong Macao Greater Bay Area.
The successful completion and acceptance of the Guangdong Unicom 400G experimental network marks the further maturity of key 400G technologies, laying a solid foundation for the future commercial and next step in the evolution of ultra high speed transmission technology. FiberHome will continue to work together with operators and customers to jointly tap the value of digital connectivity, build an all-optical base in the computing age, enable Digital transformation of thousands of industries, support the high-quality development of the national digital economy, and benefit human society.