International standards for mobile bearer technology have become a strategic commanding height for telecommunications companies in various countries due to their broad application prospects. At the just-concluded plenary meeting of the Fifteenth Study Group of the International Telecommunication Union (ITU-T SG15), China Telecom's 5G bearer technology M-OTN (Mobile-optimized OTN) core standard "25G/50G OTN interface" was successfully established. And internationally, it has won the strong support of international TIer-1 operators such as Japan KDDI, Deutsche Telekom (DT), Telecom Italia (TIM), and companies such as Huawei, ZTE, Fiberhome, Microsemi, etc., representing the mainstream international 5G bearer standard The plan proves China Telecom's ability to open up and innovate in the core field of mobile bearer and lead the development of the communications industry.
The M-OTN standard name successfully approved at this plenary session is G.709.25-50 "25G and 50G OTN interfaces" (25G and 50G OTN interfaces). The standard will define new 25G and 50G OTN frame formats, mapping and multiplexing methods, etc., to facilitate the use of pluggable Ethernet modules to reduce equipment and network costs. These interfaces will be mainly used for metropolitan area networks, including but not limited to carrying services such as 5G and dedicated lines. M-OTN is an innovative technology with OTN technology as the core. Its main features include 25G and 50G line interface technology, single-stage multiplexing, flexible time slot structure, and minimal operation and maintenance capabilities. The goal of M-OTN is to provide a low-cost, low-latency, and low-power integrated service bearing solution to support the large-scale commercial deployment of mobile networks in the future. The successful establishment of the M-OTN international standard has laid a good foundation for the extensive deployment of OTN-based 5G bearer networks.
Through years of technology accumulation, China Telecom has accumulated and made breakthroughs, laying a solid foundation for China's industrial upgrading and commercial success in the global market. While the ITU-T standard is steadily advancing, the OTN-based 5G bearer solution promoted by China Telecom has also made substantial test progress. Recently, China Telecom successfully completed the second phase of the OTN-based 5G fronthaul bearer test at the Beijing Research Institute. The test results show that one optical fiber carries one base station and the integrated service access solution (One base staTIon, One fiber) has matured. , With the conditions for commercial scale deployment. This is after China Telecom took the lead in promoting 25Gb/s single fiber bidirectional (BiDi) optical modules to complete the technical feasibility verification and the first draft of the industry standard, and to save 50% of the fronthaul fiber resources (One cell, One fiber). The second milestone achieved in the field of innovation.
In terms of mid-backhaul, China Telecom has completed the technical specifications of the OTN-based 5G mid-backhaul bearer solution and is currently undergoing laboratory testing. After passing the laboratory test, it will rapidly advance the pilot verification and large-scale application of the existing network, providing a solid guarantee for the sustainable development of China Telecom's mobile network.
China Telecom will continue to lead the direction of standards in the future development of the mobile network industry, promote the pilot and commercial use of existing networks, and implement industry advancement work.
Compared with large complex thin - wall castings, civil products have lower requirements on casting quality. However, for the latter, shorten the production cycle, improve the production efficiency of the problem becomes more prominent. The gelation process of common silica sol mainly depends on the dehydration and drying of silica sol, which takes longer time than the gelation of chemical hardening ethyl silicate. Ethyl silicate shell using ammonia dry each layer can be completed in 2h, and the final hardening of silica sol generally takes more than 12h, for some deep holes and other difficult to dry parts of the need for a longer time. At the same time, because the Investment Casting shell needs to be made in layers, each layer needs to be fully dried, to ensure that the lower shell immersion coating will not cause the problem of remelting off, and immersion coating itself, water will be immersed in the dried shell, resulting in a long overall drying cycle. It is a schematic diagram of the production cycle of silica sol shell investment casting under general conditions. As can be seen from the figure, shell making time accounts for more than 50% of the whole casting production cycle. To shorten the delivery time and shell making cycle is the core of the problem. The key factors to shorten the shell-making period can be divided into two aspects: internal cause and external cause. The main internal cause is the characteristics of the binder, and the external cause is the drying condition.
Silica Sol Casting industry in China is developing rapidly and its application is also very extensive.
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