The 21st century is an Internet-based century, and the network has become an inseparable part of people’s lives. In the near future, no matter automatic driving, VR games, online shopping and the Internet of Things or people’s social interaction and lives are more dependent on high-speed, large-capacity and low-latency networks. And such super networks cannot be achieved without ultra-long-haul and large-capacity transmission technologies.
As a world-leading provider of comprehensive communication solutions, ZTE has world-leading technologies in ultra-long-haul and large-capacity transmission, and have been successfully used in a number of domestic and overseas projects, including China Mobile’s 100G western ring project covering over 20,000 km in 2017, China Telecom’s world’s largest Reconfigurable Optical Add and Drop Multiplexer (ROADM) network with a total length of over 47,500km and covering 15 provinces, Russia’s 100G network upgrade project covering 4,000 km and Mongolia’s railway backbone network project with a total length of over 1,100 km.
With outstanding solutions and combined use of multiple technologies, ZTE won the western ring project in China Mobile’s phase-13 centralized procurement for inter-provincial backbone transport network equipment in 2020. With a total link length of 53,828 km, the western ring network after finished will not only be the world’s largest commercial OTN but also China’s first benchmark commercial network that uses C++ band (80x75Ghz) to implement 200G long-haul transmission.
The biggest challenge of the western ring network lies in high-speed long-haul transmission. ZTE uses the following cutting-edge technologies to realize this goal.
The first one is beyond 100G modulation coding technology. This project employs 200G 16QAM and 200G QPSK coding. The QPSK coding technology is used to solve the long-haul transmission problem of 200G and is put into large-scale commercial use for the first time in China.
The second one is ZTE’s proprietary beyond 100G Flex Shaping algorithm. It makes multi-point optimization at the optical and electrical layers, effectively improving the transmission distance by 30%. It also substantially reduces the use of relay boards to save the network construction costs. Flex Shaping technology includes electrical domain shaping and optical domain shaping. The former includes Probabilistic Shaping, hybrid modulation and Geometric Shaping, which can achieve longer-distance transmission in equivalent bandwidth or larger bandwidth in the same distance by adjusting the position or probability of signals in the constellation diagram at the transmitting end. The latter makes spectrum shaping for optical signals when a service passes through the ROADM sites, so as to reduce the filtering impairment on optical signals, enable more cascading ROADM sites and lengthen the transmission distance.
The third one is optical system technologies to implement beyond 100G long-haul transmission and flexible scheduling, including optical amplification technology and optical cross-connect (OXC) technology. Optical amplification makes use of optical amplifiers to compensate for signal attenuation and implement ultra-long-haul transmission without regenerators. However, the ASE noise of optical amplifiers is an important factor that affects the system OSNR. ZTE employs low-noise EDFA or high-order Raman to effectively improve the noise coefficient of the amplifiers and improve system transmission distance.
In a beyond 100G system, high-speed optical signals have more flexible spectrum and occupy different bandwidths in different modulation modes. The OXC technology not only improves the spectrum utilization but also meets the flexible scheduling requirement of beyond 100G networks. ZTE’s new-generation OXC platform can support 32-degree optical scheduling. Compared with ROADM, OXC and all-optical backplane can replace the increasingly complicated fiber connections, as they can achieve automatic optical cross-connect to effectively avoid incorrect fiber connections. At the same time, the OXC board can save about 80% space by integrating optical amplification and monitoring functions.
The OTN+OXC technology is used in large scale for the first time in the western ring project of China Mobile’s phase-13 inter-provincial backbone transport network, forming a complete optical and electrical hybrid cross-connect solution to flexibly adapt to multiple scenarios including long-haul, medium-haul and short-haul. It also implements non-blocking cross-connect and agile scheduling to efficiently transport ultra-large-capacity services, while substantially reducing the operation and maintenance (O&M) provisioning time, O&M costs of operators and the load on O&M personnel. With the successful application of long-haul transmission technologies in the western ring project of China Mobile’s phase-13 inter-provincial backbone transport network, ZTE has built more than 400 100G/Beyond 100G networks across the world, with the total fiber length exceeding 400,000 km. As an industry leader in 100G/Beyond 100G innovation technologies, ZTE will continue to invest in the R&D on ultra-long-haul transmission and ultra-large capacity. At the cutting edge of the industry, ZTE will continuously meet the new requirements of network construction in the 5G era and strive to lead the new era of high-speed all-optical interconnection.