What You Need to Know About 400G QSFP-DD SR4 Transceiver？

Author Yana

Date 11/29/2024

This article introduces the 400G QSFP-DD SR4 transceiver, highlighting its features, benefits, and applications. It also compares the 400GBASE-SR4 QSFP-DD module with the 400GBASE-SR8 QSFP-DD module, helping readers choose the best option for 400G Ethernet short-distance network deployments.

400G transceivers have become one of the most popular optical modules for next-generation data center network interconnection. Among them, QSFP-DD is the 400G Ethernet solution required by the new generation of cloud computing networks. To facilitate users in better-deploying networks, this article will introduce a 400G QSFP-DD SR4 optical transceivers for short-distance applications.

QSFP-DD 400G SR4 Optical Modules Overview

What is the 400G Ethernet?

Developed by the IEEE P802.3bs Task Force in 2017, 400G Ethernet, or 400 Gigabit Ethernet (400GbE), uses a broadly similar technology to 100 Gigabit Ethernet; however, 400G is not only four times as fast as 100GbE but also offers better economies of scale and denser configurations.

What is the QSFP-DD MSA?

As the smallest form factor for 400G optical devices, QSFP-DD can provide higher port density and is backward compatible with QSFP+/QSFP28/QSFP56. QSFP-DD complies with IEEE 802.3bs and QSFP-DD MSA standards. The electrical interface of this form factor has 8 channels. The data rate of each channel can reach 25Gb/s through NRZ modulation technology, realizing 200G network transmission; the data rate of each channel can reach 50Gb/s through PAM4 modulation technology, realizing 400G network transmission. PAM4 is one of the important technologies for achieving 400G Ethernet high-speed data transmission. To learn more about PAM4, please read this article: NRZ and PAM4: Explore the Difference.

What is the 400GBASE-SR4 QSFP-DD Module?

The 400GBASE-SR4 QSFP-DD module is a high-speed optical module based on the QSFP-DD form factor. It fully complies with the QSFP-DD Multi-Source Agreement (MSA), IEEE 802.3bs protocol, and 400GAUI-8-PAM4 standard and is specially designed for 400G Ethernet. The electrical port of the 400G QSFP-DD SR4 transceiver uses 8x50G PAM4 modulation, and the optical port uses 4x100G PAM4 modulation. It supports short-range distances up to 100m over 12 parallel multimode fiber (MMF) OM4.

What is the 400GBASE-SR4 QSFP-DD Module

Why Do We Need a QSFP-DD SR4 400G Optical Transceiver?

First, it provides higher bandwidth support. With the rapid data volume growth, traditional 100G Ethernet networks can no longer meet the needs of large-scale data exchange. The total bandwidth of 400G QSFP-DD SR4 transceivers is to 400Gbps. Such powerful bandwidth can effectively support the needs of modern data centers, cloud computing, big data analysis, and high-performance computing for large-traffic data transmission.

Second, it increases port density. The port density of QSFP-DD is double that of traditional QSFP modules, allowing more ports to be accommodated in the same physical space. This increases the port density of the data center, which is especially important for data centers with limited space.

Then, it's easy to operate. The 400G QSFP-DD SR4 optical module has plug-and-play features, simplifying the installation and deployment.

Finally, it supports backward compatibility. QSFP-DD is backward compatible with existing QSFP28 infrastructure, allowing users to easily upgrade existing equipment to support higher transmission rates.

Application Scenarios of SR4 QSFP-DD 400G Optical Module

The 400G QSFP-DD SR4 optical module is a high-performance optical transmission device designed to meet the high-speed and high-bandwidth needs of data centers, cloud computing, high-performance computing, and other fields. The following are the main application scenarios of the 400G QSFP-DD SR4 optical transceiver:

Internal data center connection: In large data centers, 400G QSFP-DD SR4 transceivers are used to connect servers and switches and interconnect storage systems, providing high-speed, low-latency data transmission.

High-performance computing cluster: In a high-performance computing environment, 400G QSFP-DD SR4 optical transceivers connect computing nodes and storage systems to support large-scale parallel computing tasks.

Cloud computing infrastructure: Cloud computing service providers upgrade their data center networks with 400G QSFP-DD SR4 modules to support higher-performance cloud services and virtualized environments.

Big data analysis and processing: In applications that require processing and analyzing large amounts of data, the 400G QSFP-DD SR4 optical transceiver can provide high-speed data transmission and speed up data processing.

Artificial intelligence and machine learning: These applications need to process large amounts of data and complex computing tasks. 400G QSFP-DD SR4 optical modules can help improve data throughput and computing efficiency.

QSFP-DD 400G SR4 vs. 400G SR8 Modules, What's the Difference?

QSFP-DD 400G SR4 vs. 400G SR8 Modules

The 400G QSFP-DD SR8 transceiver is designed for use on multi-mode optical fiber. It realizes short-distance transmission through a 16-core MTP/MPO multi-mode fiber connection, up to 70m with OM3 and 100m with OM4 fiber patch cables. It complies with the QSFP-DD MSA specification and IEEE 802.3bs protocol. It uses 8 parallel lanes at 50 Gbps each, achieving 400 Gbps data transmission. So, what is the difference between 400GBASE-SR4 and 400GBASE-SR8? The following table details their differences:

Feature	QDD 400G SR4 Modules	QDD 400G SR8 Modules
Transmission Method	Four 100Gbps lanes to achieve 400Gbps	Eight 50Gbps lanes to achieve 400Gbps
Connector Type	MPO-12 connector, requiring 12 fibers (8 in use, 4 are spare)	MPO-16 connector, requiring 16 fibers (all in use)
Distance	100m with OM4 MMF	70m with OM3 MMF 100m with OM4 MMF
Applications	400GBASE-SR4 module is ideally suited for short-haul interconnections within data centers, especially in environments where the infrastructure has deployed OM4 multimode fiber.	400GBASE-SR8 module is similar in application to the SR4, but it has the advantage of being more flexible and stable on lower-quality OM3, so it performs better where compatibility with legacy infrastructures is required.

As you can see in the table above, the QSFP-DD 400G SR4 and 400G SR8 are two different 400G optical modules that differ in areas such as transmission method and connector type. The choice between 400G SR4 and 400G SR8 depends on your network infrastructure and specific needs. QSFP-DD SR4 is typically more economical and easier to deploy because it uses less fiber, making it ideal for new installations or environments where OM4 multimode fiber is already deployed. In contrast, the QSFP-DD SR8 offers greater compatibility, the ability to support older multimode fiber types, and has advantage in distance, making it a flexible option. You can make your choice based on fiber type, transmission distance and budget.

Conclusion

The 400G QSFP-DD SR4 optical module adopts QSFP-DD form factor and PAM4 modulation technology, which improves bandwidth and port density and supports efficient network deployment. It is particularly suitable for applications such as data center connectivity, high-performance computing, cloud computing, and big data processing, providing high-bandwidth, low-latency transmission solutions. With high performance, high density and high reliability, the 400G QSFP-DD SR4 transceiver has become an ideal choice to meet current and future network bandwidth needs.