With the rapid development and wide application of 5G, cloud computing and big data, data centers are becoming the control nodes and content carriers of future networks, and their importance is becoming more and more prominent. With the scale development of data center network and the continuous upgrade and evolution of cloud computing data center network topology, the demand for higher speed, lower power consumption and lower cost for data center optical interconnection technology has been raised.
Recently, in the second online session of the "Optical Communication High Quality Forum 2021" jointly organized by China International Optoelectronic Expo (CIOE) and C114 Communications Network, the "Silicon Photonics Integration and Data Center Applications Online Seminar", He Baohong, Director of Cloud Computing and Big Data Research Institute of China Academy of Information and Communication Technology, pointed out that in recent years, data center traffic is getting larger and more complex, and has become the high point of the entire Internet traffic and business, which will inevitably lead to innovative changes at the technical level. Today, data center-oriented technology optimization and innovation has become the new craze.
Silicon photonics is one of the innovative directions for data center scenarios. With its material characteristics and the inherent advantages of CMOS process, it can well meet the data center needs for high speed, low cost and low power consumption. Cisco, Huawei, Juniper, Nokia and other industry giants have "stepped up" to silicon photonics technology through acquisitions. LightCounting, a leading market research firm in the optical communications industry, also points out that silicon photonics technology will fundamentally change the optical device and module industry.
What kind of silicon photonics solutions are needed from the user's perspective?
The development of any industry is a result of people's needs. Thus, the final landing of silicon photonics technology and the prospect of its application depends on the end users, that is, cloud computing vendors, especially the head enterprises. After all, they need to introduce new solutions in order to meet the bandwidth demand brought by high business growth, and on the other hand, to further optimize the performance and cost of their data center networks.
As a large Internet company, Tencent has super applications such as QQ, WeChat, Tencent video, Tencent games, etc. It has extremely high demand for data applications and started to lay out data centers very early, and the hardware investment has increased year by year. In recent years, in order to achieve the most optimized performance and cost for data center networks, Tencent has started to get involved in white-box switches and began to cooperate with vendors to develop its own silicon photonics modules and other products.
Hu Shenglei, Tencent optical system architect, pointed out that silicon photonics is gradually increasing its influence in the field of optical modules, and the higher rate in the future, the greater the advantages of silicon photonics. In the 400G DR4 silicon photonics module, Tencent has developed two solutions, both of which have optical module samples. However, if silicon photonics want to get the scale of commercial use, it still needs to improve its efficiency, integration, reduce the size, reduce power consumption and cost. "Silicon photonics is a technology that runs through the short, medium and long term, and silicon photonics will eventually become the dominant technology in the future."
Jingdong Technology Cloud Division optical network architect Chen Cheng pointed out that with the scale of the data center network, the network of underlay is required to achieve high throughput, easy scalability and openness. Specifically, the development direction of the optical module technology solution will develop towards high speed, low power consumption, high density, low cost and standardization. The silicon-based photonic technology, because of the characteristics of silicon materials and CMOS process inherent advantages, can well meet the above five development direction, which makes silicon photonics become the most promising optical interconnection technology solutions.
From the user's point of view, the pluggable optical module as a highly standardized product form, the user is concerned about reliability and cost. 400G and below 400G rate optical module, the traditional III-V family solutions, with years of technical precipitation, mature ecological chain, still remain competitive. For silicon photonics solutions, its advantages are mainly focused on integration and CMOS process, especially in application scenarios with high-density integration needs, such as QSFP-DD ZR, Co-Packaged, etc. Silicon photonics will have a broader market space, although it still depends on further optimization and integration of the industry.
Wang Ruixue, project manager of China Mobile Research Institute, said that the 5G operator network forms a new end-to-end collaborative architecture, and the network quality is closely related to optical modules. However, the current optical module in the carrier network deployment encountered two major challenges: First, the optical modules are used in many application areas, the room environment challenges, high requirements for the optical module environment adaptation, failure impact range is also relatively large, and the higher the rate of impact range is larger; Second, the optical module procurement costs are relatively high, the operating power consumption is also relatively high, resulting in high network operation and maintenance costs.
Wang Ruixue pointed out that silicon photonics technology is a collection of low-cost, low-power, high-speed and highly integrated advantages, and has great space for development. The silicon photonics module will be fully integrated with the optical/electrical chip on the silicon photonics chip to realize the manufacturing of optical modules, thus effectively reducing the material cost, chip cost and packaging cost.
The industry chain is in place, and silicon photonics solutions are ready
After more than ten years of development, silicon-based photonic technology has formed a more complete industry chain, from design flow to packaging and testing to system integration, many companies are participating in this market. As of today, there are already large-scale deployments of product types, including 100G PSM4 and CWDM4 as well as coherent optical products.
According to "Moore's Law" in the field of optoelectronics, optical modules evolve by one generation every four years, and the bit cost drops by half and power consumption drops by half. So, the 100GE optical interconnect technology born in 2016 is at the crossroads of forward evolution, and 400GE becomes the next generation optical 400GE has become the preferred solution for next-generation optical interconnect.
Currently, data center 400G optical interconnect solutions include traditional III-V family solutions and silicon photonics solutions. According to Zhou Libing, the opportunity for silicon photonics solutions in 400G lies in solving the challenges of optical power & power consumption, reducing packaging components through integration, lowering packaging costs, and leveraging the inherent advantages of silicon photonics chip mass production to achieve commercial success. In addition, with the further evolution of optical interconnect density and bandwidth, silicon photonics will have obvious advantages, especially in new data center application scenarios such as co-location and coherent.
Zhang Hanzheng, vice president of optical network business of Nokia Bell, introduced that Nokia Bell is continuing to promote silicon photonics innovation, able to provide photonic design toolset for rapid customization of silicon photonic design; RFIC co-design to achieve independent design and match silicon photonics engine; advanced packaging to provide multi-chip modules, flip chip BGA; manufacturing innovation to provide wafer-level assembly and testing.
According to Zhang Jinshuang, Business Development Director of Eoptolink, as data center traffic continues to grow rapidly, the key requirements of data centers for optical modules are nothing but high speed, high density, low cost and low power consumption, and silicon photonics integration technology has become a reliable solution to meet these challenges. At present, Eoptolink has already launched 400G QSFP-DD silicon photonics module, which has the advantages of performance, cost and supply. The next step of Eoptolink will improve the package coupling efficiency by optimizing the design and process.
As data center switching capacity doubles every two years, pluggable optical modules are evolving towards co-packaged optics (CPO), according to Fang Yi, director of application engineering and market development at Corning Optical Communications. And CPO requires increasingly dense optical connectivity, a process that requires innovation in fiber-chip coupling, special fibers, fiber management, panel optical connectivity systems, and all other components that span optical connectivity solutions. Corning is currently able to provide all of the original components for first-generation CPO connectivity while presenting a vision for further optimized glass substrate solutions.
Feng Junbo, director of the Center for Silicon Based Optoelectronics at the United Microelectronics Center (CUMEC), introduced that silicon-based optoelectronics technology can be closely integrated with microelectronics due to its compatible ecosystem with microelectronics, which is the source of the strong vitality of silicon-based optoelectronics technology. In the early stage of the development of silicon-based optoelectronics technology, the small market share (compared with microelectronics) is difficult to match with CMOS process, which is highlighted by the difficulty to find a suitable R&D and production platform for silicon-based optoelectronic chips. CUMEC's open platform for silicon-based photonics can provide the whole process capability from chip design to production and manufacturing to packaging and testing.
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