Silicon Photonics Illuminates the Path to Sustainable Development for Data Centre Networks

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With the advancement of Internet technology, data centres are progressively evolving into "computing power centres." High-performance applications, such as artificial intelligence and machine learning, are experiencing rapid development, leading to the emergence of various business sectors, including autonomous vehicles, big data streaming, and interest-based e-commerce. As the supporting infrastructure adapts to applications like artificial intelligence and machine learning, GPU (Graphics Processing Unit) computing clusters impose more stringent requirements on network transmission than CPU (Central Processing Unit) general computing clusters. This phenomenon is commonly referred to as the evolutionary model of "business-driven network iteration." In this framework, network iteration commences with high-performance GPU scenarios to address premier business demands and subsequently broadens its support to encompass more general scenarios, thereby maximizing the benefits derived from technological advancements.

Figure 1: Schematic diagram of data centre network architecture

In addition to the direct demands from the business sector, enhancements to various facilities within the data centre to satisfy functional requirements are also indirectly influencing the advancement of network equipment. For instance, GPU servers utilizing the next-generation H100 necessitate a network access bandwidth of 400G; furthermore, the next-generation CX7 smart network card requires that the network access switch supports PAM4-112G SerDes (Serializer / Deserializer).

Driven by the dual imperatives of business needs and hardware innovation, the upgrading of the data centre network architecture is essential. To achieve this iteration, the technologies at three levels—switching chips, SerDes, and optical modules—must advance in a coordinated manner, as each component is integral to the overall process. It is evident that this trajectory of technological evolution will encounter numerous challenges, with power consumption being a particularly complex issue to address.

Figure 2: Factors Driving the Iterative Upgrading of Data Centre Networks and Power Consumption Challenges

Commencing with the evaluation of switch chips that influence switch performance, it is observed that advancements in switch chip technology have led to a reduction in power consumption per bit. However, concomitant with the increase in switching bandwidth, the aggregate power consumption of switch chips utilized in data centres continues to rise annually. In addition, to switch chips, serializer - deserializer (SerDes) circuits and optical modules significantly contribute to the escalating power consumption. Data analysis reveals that the overall power consumption of a single switch in 2022 is 22 times greater than that of a single switch in 2010. Additionally, the power consumption associated with SerDes chips has amplified by a factor of 25, while the power consumption of optical modules has increased by 26 times.

In examining the evolution of optical modules, it is noteworthy that in 2007, the power consumption of a 10G optical module was less than 1 watt. However, as advancements have been made from 40G and 100G to the contemporary 400G and 800G optical modules, and with the anticipated introduction of 1.6T optical modules, power consumption has escalated dramatically, nearly reaching 30 watts. In scenarios where a switch is fully equipped with 1.6T optical modules, the power consumption becomes profoundly significant.

The technological advancements of traditional pluggable optical modules are insufficient to support the sustainable development of data centres, which can be primarily observed in four critical areas:

Figure 3: The bottleneck in the development of traditional pluggable optical module technology

The realization of signal integrity (SI) encounters significant material bottlenecks. In the context of high-speed telecommunications signal transmission via printed circuit boards (PCBs), the utilization of traditional pluggable optical modules presents challenges related to signal transmission distance and loss. The extended transmission distance contributes to notable signal degradation, posing significant obstacles to achieving robust signal integrity. Additionally, the development of lower-loss, mass-producible PCB materials faces numerous technical challenges that impede progress.

Moreover, power consumption presents another critical issue. A fully loaded 1.6T module device exhibits substantial power demands, which complicates heat dissipation design, including associated requirements for cabinet power supply. The escalation of power consumption leads to a corresponding increase in total equipment costs, including supplementary expenses related to utilities such as electricity and cooling. This dynamic consequently elevates the initial investment required for network infrastructure development.

Furthermore, product design challenges arise. Systems that employ traditional pluggable optical modules necessitate intricate system designs to accommodate 128 ports, while also addressing technical concerns related to the thermal management of high-power optical modules. This complexity contributes to elevated system costs.

In summary, Ruijie Networks aims to address the power consumption challenges within the iterative data centre network architecture, which encompasses switching chips, SerDes technology, and optical module innovations. The objective is to establish the next generation of green, energy-efficient, and sustainable data centres. By leveraging customer business scenarios and product practices, Ruijie Networks presents innovative solutions and technical recommendations for sustainable data centre networks, organized into three distinct layers.

The foundational layer focuses on architecture upgrades grounded in next-generation chips, SerDes, and optical module technologies to facilitate iterative enhancements of the network architecture, thereby accommodating the ever-growing bandwidth requirements of applications such as artificial intelligence and machine learning. Building upon these architectural upgrades, the initiative begins with network devices to address the existing power consumption issues associated with SerDes and optical modules. It is essential to recognize that these challenges are not exclusively confined to the current generation; every future generation of network architecture will inevitably confront similar issues. Consequently, it is imperative to envision a sustainable development trajectory for data centre networks that prioritizes cost-efficiency and low power consumption.

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