Recently, China Telecom Group Corporation organized its research institute and jointly with partners such as Huawei, ZTE, FiberHome and Shanghai Nokia Bell, successfully completed the single-wave 800G/400G live network hybrid rate transmission system test on the existing network between Nanjing and Shanghai. They achieved a maximum transmission capacity of 64 Tbit/s and a non-electrical relay transmission over a distance of more than 1,200 kilometers, confirming the technical feasibility of 800G/400G hybrid transmission.
For this landmark event, Huo Xiaoli, director of the Transmission Network Research Center of China Telecom Research Institute, accepted an exclusive interview with C114 and systematically expounded the value and significance of the 800G/400G multi-rate hybrid transmission pilot. “The continuous growth of industrial digitalization and intelligentization demands has led to the continuous improvement of network capacity, performance requirements and intelligentization requirements,” Huo Xiaoli said. As the next-generation high-speed transmission technology, 800G/400G multi-rate hybrid transmission has technical leading advantages and can better meet the needs of future networks and accelerate the ability to provide high-speed services. As the leading unit of the original technology source of the next-generation optical network, China Telecom has an unshirkable responsibility to lead the development of new technologies and promote their applications.
Follow the trend and break through the key technologies of wavelength bands
To achieve 800G/400G multi-rate hybrid transmission, higher requirements are imposed on trunk network resources. Huo Xiaoli pointed out that, first of all, high-quality existing network fibers are needed to ensure transmission performance. Secondly, for optical cable Mesh networking, it is best to have direct optical fiber connections between nodes to avoid performance and delay losses caused by detours.
It is understood that since China Telecom first built the low-loss G.654E commercial link in 2018, it has been constructing such optical cables on a large scale across the country. Meanwhile, China Telecom is accelerating the creation of a backbone optical cable artery featuring “four regions, six axes, eight hubs, multi-channels, international and domestic integration, and zonal radiation”, increasing the orientation of regional optical cables to meet the efficient carrying capacity of 400G and higher-rate transmission systems and support the construction of a green and low-carbon all-optical network.
Of course, to achieve large-scale applications, a series of key technologies need to be broken through. For example, breakthroughs in single-wavelength ultra-high-speed technologies, including optoelectronic devices that support high symbol rate transmission, high-performance digital signal processing chips, etc.; extended band technologies, including optical amplifiers that support extended bands, wavelength selective switches, and wide-spectrum tunable light sources, devices oriented towards the integration of extended C+L bands, and power management technologies for extended bands.
It is worth noting that the formation of a three-dimensional networking architecture through multi-rate hybrid transmission is a new networking method that is currently less applied in operator networks. Huo Xiaoli introduced that compared with the current situation where one rate corresponds to one network, which is more commonly applied, there is a lack of experience in network optimization and operation and maintenance, and new challenges will be faced.
In Huo Xiaoli’s view, the characteristics of the 400G/800G multi-rate hybrid transmission system need to be comprehensively considered at the network planning stage, and the concept that planning is the precondition for maintenance should be established. China Telecom has a complete system, perfect regulations, and rich experience, and has independently developed and applied a complete set of maintenance management systems, while introducing AI technology to enhance network planning and operation and maintenance efficiency.
