In the contemporary, swiftly evolving landscape, the call for swift data transmission has reached unprecedented heights. The advent of AI applications and expansive models, exemplified by entities like ChatGPT, has positioned computational prowess as an indispensable foundation for the AI sector. In response to the escalating need for expeditious communication in supercomputing, high-speed optical modules have morphed into integral elements for AI servers. This discourse explores the notable strides in 800G optical transceivers and their vast potential in the AI epoch.
Escalating Bandwidth Imperative: The surge in bandwidth demand has profoundly influenced high-speed optical modules. Conventional 100G, 200G, and 400G optical modules, unable to fully satiate market demands amid the proliferation of emerging technologies and the imperative for large-scale data transmission, have paved the way for the ascendance of 800G optical modules.
Unveiling the Promise of LPO Technology: In the realm of 800G optical transceivers, Linear-drive Pluggable Optics (LPO) technology emerges as a sanguine resolution. LPO employs linear analog components in the data link, obviating the necessity for intricate CDR or DSP designs. In contrast to DSP solutions, LPOs present noteworthy reductions in power consumption and latency, rendering them ideal for the exigencies of short-range, high-bandwidth, low-power, and low-latency data connectivity in AI computing centers. As cloud service providers amplify their computational reservoirs, LPO solutions, encompassing 800G LPO, are poised to secure a substantial market share.
Electrical and Optical Interface Architectures of 800G Ethernet: Research intimates that aligning the single-channel speed of electrical and optical interfaces optimizes the architecture of optical modules, ensuing in diminished power consumption and cost-effectiveness. For instance, an 8×100 Gbit/s optical transceiver accrues benefits from a single-channel 100 Gbit/s electrical interface, while a 4×200 Gbit/s optical transceiver harmonizes effectively with a single-channel 200 Gbit/s electrical interface. The configurations of 800G optical transceivers may adopt varied formats, including the double-density four-channel small form-factor pluggable (800G QSFP-DD) and eight-channel small form-factor pluggable (800G OSFP).
There exist three primary optical interface architectures for 800 Gbit/s optical transceivers:
8×100 Gbit/s PAM4 Optical Transceiver: This transceiver functions at 53 Gbd and employs eight pairs of DACs and ADCs, eight lasers, optical transceivers, and a pair of 8-channel coarse wavelength division multiplexing (CWDM) or LAN-WDM multiplexer and demultiplexer.
4×200 Gbit/s PAM4 Optical Transceiver: Operating at 106 Gbd, this transceiver employs four pairs of DACs and ADCs, four pairs of optical transceivers (including four lasers), and a pair of 4-channel CWDM or LAN-WDM multiplexer and demultiplexer.
800 Gbit/s Coherent Optical Transceiver: Operating at 128 Gbd with 16QAM modulation, this transceiver utilizes four pairs of DACs and ADCs, one laser, and one pair of optical transceivers. Additionally, data center coherent optical modules can integrate fixed-wavelength lasers to reduce costs and power consumption.
The evolution of 800G optical transceivers is nascent and is poised to progress over the ensuing half-decade. Key trends encompass:
Single-Mode Migration: The industry is pivoting towards single-mode optical interface solutions, capitalizing on SiPh (Silicon Photonics) technology to overcome the bandwidth limitations of multimode fibers, which restrict the transmission distance of 100 Gbit/s PAM4 VCSEL+multimode fibers to 50 meters.
Arrival of Single-Wavelength 200 Gbit/s: Advancements in 112 Gbd EML (Electroabsorption Modulated Laser) technology, despite the somewhat restricted availability of 55 GHz bandwidth resources, hold promise. The future anticipates the role of SiPh modulators and silicon-based thin-film lithium niobate in enabling 200 Gbit/s single-wavelength solutions.
Coherent Migration: Coherent technology solutions are expanding their reach to shorter distances (40, 20, and 10 km) in addition to the existing 80 km range. Non-coherent solutions are also extending their reach to longer distances. Coherent solutions, by utilizing one laser, modulator, and receiver compared to PAM4's requisite four of each, maintain cost competitiveness. Despite the complexities at 800 Gbit/s, these devices effectively curtail system costs, ensuring PAM4's competitiveness. The ongoing competition between coherent and PAM4 transmission necessitates vigilant observation to decipher the ultimate outcome.
Why is 800G More Pivotal than 400G for AI Servers?
Primarily, AI servers mandate high data transmission rates and low latency, necessitating top-of-rack switches that align with the underlying bandwidth. These switches may additionally require latency redundancy, demanding high-speed optical modules. For example, the NVIDIA DGX H100 server, furnished with 8x H100 GPU modules, where each GPU necessitates 2x 200G optical modules. Consequently, each server mandates a minimum of 16x 200G modules, and the corresponding top-of-rack switch ports necessitate at least 4x 800G.
Furthermore, 800G optical chips offer superior cost efficiency and economic advantages. They leverage 100G EML chips, as opposed to 200G/400G, which employs 50G optical chips. Calculations unveil that, for the same rate, the cost of a 100G optical chip is 30% lower than that of two 50G optical chips.
Nevertheless, it is crucial to acknowledge the significance of 400G optical transceivers in the industry. While they may not match the speed of 800G optical transceivers, they deliver a substantial enhancement in bandwidth compared to older technologies, positioning them as a cost-effective solution for numerous organizations. Moreover, specific applications may not necessitate the full capabilities of an 800G Ethernet, rendering a 400G Ethernet a more pragmatic choice.
T&S extends a comprehensive array of high-speed optical network products and holistic HPC networking solutions to clients across diverse sectors, encompassing Financial, Healthcare, Education, Government, and Telecom. To furnish cutting-edge optical connectivity solutions, T&S has introduced 400G and 800G optical transceiver products on its official website.
To encapsulate, in the face of the burgeoning need for swifter and more efficient data transmission, the epoch of 800G optical transceivers has dawned. Armed with their extraordinary bandwidth capabilities and strides in LPO technology, these transceivers are on the verge of reshaping the AI sector and revolutionizing data centers. The deployment of 800G optical transceivers propels us closer to realizing the complete potential of AI.