Moving towards the supercomputing era, data centers have ushered in rapid development. With the continuous evolution of technology, the rise of AI supercomputing is leading the wave of innovation in the digital field. In this era with data as the core, the demand for data centers is not only the expansion of scale, but also the urgent desire for high-speed transmission. The transmission rate of 400G/800G, just like a powerful digital trend, is redefining data centers infrastructure.

In this article, Gigalight introduces you to a brand new 400G product: 400G QSFP-DD SR4 optical module, and see how it is used in today’s data centers.

Existing 400G network solutions

The high-speed network in the GPU cluster mainly consists of high-speed network cards, optical connectors (optical transceivers and cables) and high-speed switches. Currently, servers equipped with H800GPU mainly use NVIDIA CX7 400G network cards, and there are many choices of switches on the market. These options include 64400G QDD switches based on BCM 25.6T Tomahawk4 (TH4) chips, 64800G switches based on BCM 51.2T chips, switches based on Cisco Nexus chips, and 400G/800G switches based on NVIDIA Spectrum chips. From a market perspective, 400G QDD switches are currently the dominant choice. The following figure shows the commonly used network architecture of clusters:

It can be observed that the mainstream 400G switches in the market use 56G SerDes, while the CX7 network card uses 112G SerDes. In order to keep the network connected, this difference needs to be considered when selecting optical transceivers to ensure component compatibility and proper operation. As shown in the picture:

In order to solve this problem, everyone currently chooses 400G QSFP-DD DR4 optical modules on the switch side, and uses 400G OSFP DR4 optical modules on the server side. The connection is shown below:

This is a good solution within a connection distance of less than 500m, but if the connection distance does not exceed 100m, choosing the DR4 solution is a bit wasteful. Therefore, the short-distance 400G QSFP-DD SR4 using low-cost 850nm VSCEL laser is a good choice. It is much cheaper than DR4 and can meet the transmission distance requirement of 100m.

400G QSFP-DD SR4 is inserted into the 400G QSFP-DD 8×50G PAM4 port, which can be interconnected with the 400G OSFP (4×100G PAM4) network card, and the interconnection between 400G QSFP-DD SR4 and 400G OSFP SR4 can be realized. . If shown:

Gigalight’s newly launched 400G QSFP-DD SR4 electrical port uses 8×50G PAM4 modulation, and the optical port uses 4×100G PAM4 modulation. Compared with 400G QSFP-DD SR8, it reduces 4 lasers and achieves lower Power consumption and price, power consumption is less than 8W. Using MPO12 optical port, it can meet 60m transmission with OM3 multi-mode fiber, and 100m transmission with OM4 multi-mode fiber.

The release of Gigalight’s 400G QSFP-DD SR4 fills the gap in short-distance 400G data center interconnection solutions and provides a more comprehensive choice for your data center.