Zhang Chengliang, China Telecom: Opening All Optical Network 2.0 in an All-Round Way to Meet the Challenge of 5G Business
Post Time:2019-07-09

        C114 News July 8 (Leth) During the World Mobile Congress (MWCS 2019), Zhang Chengliang, deputy general manager of China Telecom Science and Technology Innovation Department, said that driven by the demand of 5G and cloud era business, large bandwidth and low latency become the core demand. All-optical network 2.0 can be used. To achieve wavelength-level scheduling, rapid service deployment and ultra-low delay, improve the overall efficiency of network.

         The development of 5G brings forward new demands for bearer network      
          As a new generation of communication standards, 5G Dangren has become the current focus of the industry. In addition to the network, industry applications are also the key target of 5G commercial operators. According to incomplete statistics, global operators have laid out more than 50 vertical industry application scenarios according to the three major application scenarios of 5G. Among them, vehicle networking, intelligent manufacturing, high-definition video, AR/VR, telemedicine and smart city are the focus of attention. This puts forward higher requirements on network bandwidth, connection density, delay, synchronization, cost and efficiency for 5G bearer network.           

        The key requirement of 5G bearer is large bandwidth and low delay. Based on the statistics of 196 5G Demo/Trail case reports, the majority of 181/196 downlink throughput rates exceed 1-5 Gbps, with the largest proportion range of 1-5 Gbps. Based on the 5G delay distribution of 69 5G Demo/Trail cases, most cases are within 2ms, most cases are within 5ms, and the proportion is 1-2ms.

       Zhang Chengliang believes that the top priority of 5G construction is from optical fiber to base station. Deloitte's consultation report "Communication Network Infrastructure Upgrading - Demand for End Fiber" pointed out that the success of 5G wireless depends on End Fiber. For example, the U.S. network does not have enough optical density to support the bandwidth requirements of future 5G applications; without more end-to-end optical fibers, operators will not be able to support the expected growth of mobile data traffic of more than four times between 2016 and 2021. The report predicts that in the next five to seven years, the United States alone will need to invest $130 billion to $150 billion in optical fiber infrastructure to fully support 5G broadband competition, rural coverage and wireless encryption.   
        Access to convergent computer room (or integrated service station) has a strategic position for operators, and the sinking of OTN/WDM to this position is the key step of integrated bearing. According to reports, at present, China Telecom is comprehensively carrying the load to promote the sinking of OTN/WDM. Based on the demand and bandwidth estimation of integrated services, the sinking of OTN/WDM to access convergence point will realize integrated services carrying. Access layer network nodes are usually deployed on demand according to different types of operation and maintenance (5G, dedicated line, home broadband, etc.), but it is difficult to achieve comprehensive bearing.

         Zhang Chengliang pointed out that compared with 5G, 4G is not only changing the network architecture, but also putting forward higher requirements for core network, mid-stream/back-stream, forward-stream and so on. Core networks require faster optical modules (200G/400G), larger capacity of optical transmission, more flexible networking, and more efficient optical layer scheduling. Upload/return requires faster optical modules (50G/100G), larger network bandwidth, more flexible networks and better performance. Forward transmission requires more optical fibers, faster optical modules (25G) and better performance.

        For 5G forward transmission, Zhang Chengliang believes that optical fiber should be the main factor, so the advantages of this deployment outweigh the disadvantages. Advantages are: the scheme is simple and the cost of single-fiber bi-directional filter increases very little. Only one optical fiber is needed for each sector, which can save 50% of the core. In addition, the industrial support is good, and the laboratory has preliminarily tested the samples of several manufacturers, which fully meet the requirements of the standard. At the same time, the two-way optical fibers are consistent, and the synchronization accuracy is high.

         The disadvantage is that the cost of BiDi module is slightly higher than that of traditional single-fiber module. Typical application scenarios of 5G prequel include: CRAN scenarios deployed by AAU and DU/CU. The industry mainly focuses on two specifications: 10Km and 15Km. AAU and DU/CU co-location deployment of optical fiber resources, optical cable new difficult DRAN scenarios, to solve the rapid deployment problem.   

       Compared with forward transmission, middle/return transmission requires more flexible optical network bearer technology. Zhang Chengliang pointed out that OTN bearer can better solve the problem of large bandwidth and low latency, but flexibility needs to be enhanced.

        Full deployment of all-optical network 2.0   

         All-optical network is the most ideal carrier technology for 5G. China Telecom's all-optical network "2.0 era" has been fully opened. "Only when all transmission, switching and access are implemented in the optical domain, and ROADM and OXC are introduced into the switching layer, can an all-optical network be formed in the strict sense." Zhang Chengliang said.   

         At present, ROADM has been widely deployed in China Telecom. China Telecom has carried out ROADM application practice in South China, which is also the first intelligent ROADM backbone network in China. According to reports, ROADM network in South China mainly carries IP100G and part of 100G dedicated line services, covering 27 nodes and 79 links. All nodes adopt 20-dimensional ROADM, which guarantees enough flexibility and directionality. WSON function is enabled to provide routing recovery function for upper layer services, which reduces the impact time on IP links when optical cable failures occur.

        In addition, the application of ROADM in Shanghai Telecom MAN is the first 20-dimensional ROADM large-scale application network in the industry, which guarantees sufficient flexibility and directionality of routes. Grouping enhanced OTN meets the needs of government and enterprise business.     

       Zhang Chengliang pointed out that OXC is the next step in the development of optical cross-over technology. OXC technology has three key innovations: the first light backplane. All-optical interconnection, connectionless optical fiber; high integration; one direction and one slot, innovative multi-level dust control technology, high reliability, connectionless, low insertion loss. Second, low cost, 32 dimensions. Super large cross capacity 320T-640T, light-free CDCG, high reliability. Third, digital optical layer. The real-time wavelength information visualization is realized by using OFDM tuning and high-precision wavelength monitoring technology. Visualization of optical fiber quality, wavelength level performance, wavelength utilization, wavelength path and so on.  

        Overall, OXC backplane architecture can achieve no fibrillation connection and avoid complex and tedious fibrillation work in the case of super-large capacity. In addition, optical fiber alignment, dust-proof technology and other engineering and maintenance-related technologies have made breakthroughs. It is expected that commercial products will be launched as soon as next year. Compared with ROADM, it will be more convenient to schedule the optical layer.

Source: C114 Communication Network