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中文
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At the standard level, ITU-T has formulated standards and specifications for three consecutive years from 2016 to 2018, and OIF has started relevant work in 2015. The domestic CCSA has also successively issued 400Gb/s WDM system technical requirements. At the industrial level, it was even earlier. In 2011, when Nokia's name still existed, OFC reported the first 400G 600km SMF transmission experiment. At the application level, after system equipment vendors released related products one after another, many operators around the world began to experiment. It can be said that all parties in the industry chain are in full swing, but the reality is very skinny. LightCouting predicts that the deployment of 400GbE by the five major Internet/cloud giants will begin to enter the platform period in 2021-2022; from the perspective of the entire global market, 400GbE will continue to grow until 2026. Omdia believes that 400GbE optical modules will begin large-scale commercial use this year, driven by the need to reduce power consumption and cost; from the perspective of application scenarios, FR4 (2km) and DR4 (500m) are the most important interface types in the long run. So, how long will the scale of 400Gbs DWDM be fully commercialized?
The first is whether the technology will work?
For the 400G client side, due to the long period of 400GbE from hype to commercial use, with the development of technology, too many technical solutions have been produced, each of which cannot be mass-produced. At present, 400GbE optical module technology is gradually focusing on the single-wavelength 100Gb/s PAM4 solution. (2km\10km). The 400G OTN optical module has complete standards (ITU-T G.709, G.959.1), but the product is lacking. There is no dual-rate optical module compatible with 400GbE/400G FlxO-SR on the market. For telecom operators, why is the 400G OTN customer-side optical module important? For the carrier backbone network, cross-system transfer is inevitable, and OTN client-side interconnection is the best choice for cross-system transfer of the backbone network. Therefore, the 400Gb/s WDM system requires a mature 400G FlexO-SR interface, and the industry needs to provide dual-rate optical modules compatible with 400GbE and 400G FlexO-SR as soon as possible, with specifications focusing on FR4 and LR4-6. In addition, there is no compatible PAM4 DSP chip that supports 53.125Gbps and 55.9Gbps dual rates at this stage, and it is urgent that the chip mature as soon as possible. For the 400G line side, single-carrier 400Gb/s line-side technology is the development direction. In DCI/metro/regional scenarios, the PM-16QAM solution (including the constellation shaping solution) is mature and has commercial conditions. However, in the ultra-long-distance backbone network, there is currently no mature single-wavelength 400Gb/s PM-QPSK modulation transmission equipment. The bottleneck is 130+Gbaud high baud rate chips and devices, which limits 400Gb/s DWDM to a certain extent. Scale deployment of the system
The second is whether the internal and external conditions are enough?
Looking at the client side first, the core routers and data center outlet switches 400GbE are ready, and the equipment supports the ability to upgrade 400GbE ports at any time. The reason why operators have not yet deployed on a large scale is that the unit bit cost of long-distance optical modules is still higher than 100GbE. On the line side, in scenarios such as DCI, metro/regional core interconnection, etc., as the unit bit transmission equipment cost is beginning to approach or even lower than 100Gb/s, a certain scale of application will soon be ushered in. In backbone/ultra-long-distance scenarios, the performance of 96Gbaud products is limited, 128Gbaud products are not yet mature, and the unit bit maturity is still higher than 100Gb/s. The deployment prospects depend on whether there is a clear 400GbE bearer requirement. In addition, the ultra-low loss and large effective area G.654E optical fiber is conducive to greatly improving the transmission performance of 400Gb/s WDM systems, and the construction progress of the operator's G.654E optical cable significantly affects the commercial rhythm of single-wavelength 400Gb/s ultra-long-distance transmission systems. China Telecom's Shanghai-Guangzhou G.654E optical fiber backbone optical cable project started in 2018 and will be completed in 2021. The entire site is about 2,000 kilometers. The test results show that the current network transmission distance of the single-wavelength 400Gb/s DWDM system based on 90+Gbaud is expected to reach about 1500km in G.654E optical fiber; it is expected to reach 800-900 kilometers in G.652 optical fiber.The cost performance of G.654E determines that it is only suitable for backbone transmission "niche" scenarios (relative to the total amount of transmission fiber), and the industry chain has a risk of sustainable development. Call for the promotion of G.654E fiber deployment as a national innovation strategy; operators and other end users should plan and coordinate the construction of G.654E to avoid major ups and downs and promote the sound development of the industrial chain; fiber manufacturers must further optimize and normalize technical parameters and processes. Ensure G.654E fiber compatibility of different manufacturers.
Finally, is the cost expensive?
For the first use where it is affordable, the cost of short-distance 400GbE optical modules in data center scenarios is low, and the comprehensive cost performance is likely to exceed 100GbE. For DCI/metropolitan area 400Gb/s DWDM transmission, the unit bit transmission cost is close to or lower than 100Gb/s DWDM. To use low-cost solutions as much as possible, and reuse DC solutions as much as possible in telecom scenarios, such as 400GbE 500m and 2km optical modules, 400GbE LR-10km can be optimized to LR-6km. Part of it is ready. In addition to cost, the limiting factors are important technical bottlenecks that need to be overcome in the backbone long-distance transmission scenario, especially 400G ETH/FlexO-SR dual-rate client-side optical modules and line-side single-wavelength 400Gb/s PM-QPSK Two core bottlenecks such as key chips and components.
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