Recently, we’ve received numerous inquiries from users about 400G optical modules. As a mainstream optical module type today, there are several key issues drawing the most attention.

About 400G Data Center Switch

Q1: Does Asterfusion offer 400G switches?
A1: Absolutely! Asterfusion offers a cutting-edge 400G switch, specifically our self-developed 12.8T switch, which is powered by our enterprise version of SONiC NOS—AsterNOS. This switch is engineered to meet the demanding requirements of various applications, including AI, machine learning, data centers, high-performance computing (HPC), and distributed storage. Curious to learn more? Check out Asterfusion’s product page for all the details!

Regarding Packaging Questions:

Q1: What is the difference between QSFP-DD and OSFP optical modules?

A: QSFP-DD has a smaller size, making it ideal for data centers with space constraints. It is best suited for environments where backward compatibility and high port density are essential. OSFP modules are slightly larger and have higher power consumption, better suited for telecom applications. Comparatively, QSFP-DD offers four-lane small size and double port density, whereas OSFP supports 8 high-speed electrical lanes.

Q2: May I know Pros and Cons of OSFP and QSFP-DD?

A: OSFP’s size cannot accommodate certain optical-electrical interfaces, while QSFP-DD, based on the QSFP size, adds an extra row of electrical pins, achieving excellent backward compatibility with 40G and 100G QSFP modules and QSFP28 modules. In terms of transmission power, OSFP modules integrate heat sinks within the module casing, offering a larger heat dissipation area, optimizing heat transfer and providing superior thermal performance compared to QSFP-DD modules.

Q3: What is QSFP112 packaging?

A: QSFP112 is a module and cage/connector system based on the current QSFP design, intended to support 112Gbps per lane in a 4-lane QSFP system and enable a 400G QSFP interconnect ecosystem. This greatly helps traditional QSFP users upgrade link bandwidth to 400G per port with lower costs and shorter transition times.

Q4: Why Do We Need QSFP112?

A: For intra-data center networks, transitioning from 200G (QSFP56) to 400G (QSFP112) allows for reusing existing fiber pathways, avoiding the need to reconfigure fiber layouts when evolving directly to 800G. QSFP112 is the most convenient and cost-effective way to upgrade data center network bandwidth, maintaining physical and logical consistency in network architecture from 200G to 400G. QSFP more easily manages the challenges of signal integrity and heat at higher speeds. Implementing 400G QSFP112 also opens a potential pathway for future 224G per channel speeds.

Q5:QSFP112 Backward Compatibility?

A：Yes, expected changes in connectors and enclosures do not impact backward compatibility, allowing acceptance of traditional QSFP56 and QSFP28 modules, including optical transceivers, active and passive copper cables.

Q6: What are the common and popular types of 400G optical modules on the market?

A: The commonly available 400G QSFP-DD optical modules on the market include: QSFP-SR4-400G, QSFP-DD-SR8-400G, QSFP-DD-DR4-400G, QSFPDD-FR4-400G, QSFPDD-SR4.2-400G, QSFP-DD-DR4-400G, QSFP112-DR4-400G, QSFP-DD-LR4-400G, QSFP-DD-LR8-400G

For more about above questions: Choosing the Best 400G Module Packaging: QSFP-DD, OSFP, or QSFP112—Which Fits Your Needs?

Compatibility Questions:

Q1: Can an OSFP optical module be used on one end of a 400G link while a QSFP-DD module is on the other end?

A: Absolutely! As long as both modules adhere to the same protocol standard, OSFP and QSFP-DD optical modules can work together seamlessly. The key is that they follow compatible protocols, despite their different physical dimensions.

Q2: Can a 400G OSFP optical module be used in a QSFP-DD port?

A: Not quite. Due to the differences in physical size and incompatible connector protocols, a 400G OSFP optical module cannot be inserted into a QSFP-DD port. Each module has been designed for specific applications, so it’s essential to match them correctly!

Q3: Can an OSFP optical module be inserted into a QSFP-DD port?

A: Nope! These two formats are incompatible due to their differing sizes. If your equipment is designed for OSFP, it’s best to stick with OSFP optical modules, Direct Attach Copper (DAC) cables, or Active Optical Cables (AOCs) to ensure optimal performance.

Q4: Can a 100G QSFP28 optical module be inserted into an OSFP port?

A: Unfortunately, no. A 100G QSFP28 module cannot be directly plugged into an OSFP port. However, if you really need to bridge that gap, a converter module can be used to adapt it—just keep in mind that the link will still operate at 100G speeds.

Technology Questions:

What is PAM4? What is the difference with NRZ?

PAM4 (Pulse Amplitude Modulation with 4 levels) is a cutting-edge modulation technology that takes data transmission to the next level. Unlike NRZ (Non-Return-to-Zero), which uses just two signal levels for transmitting data (representing 1 or 0), PAM4 uses four distinct signal levels to represent two bits of data per symbol period. These four levels—0, 1, 2, and 3—allow for a more efficient use of bandwidth.

What does this mean in practice? At the same baud rate, PAM4 can double the throughput of NRZ, effectively increasing network capacity without needing additional optical fiber. This results in a significant boost to bandwidth efficiency, allowing networks to scale without major infrastructure upgrades.

Why Does PAM4 Matter?

By using higher-order modulation, PAM4 helps reduce the number of optical devices required for data transmission. This not only lowers the performance demands on optical devices but also strikes a balance between cost, power consumption, and network density—a crucial factor for data centers looking to maximize efficiency.

Historically, PAM4 was considered a promising alternative for 100G Ethernet standards, but it faced challenges due to cost and technology maturity. However, with the advancements in 25G and 50G baud rates, PAM4 is now widely adopted in modern data center environments, powering high-speed 200G and 400G Ethernet links.

In short, PAM4 is the technology enabling the next wave of high-capacity networking, offering both performance gains and cost-effective scalability.

What factors should be considered when choosing a suitable 400G module?

Choosing the right 400G optical module is a multifaceted decision that requires careful consideration of compatibility, performance, power consumption, cost, and future scalability. By evaluating these factors, you can select a module that not only meets your current needs but also positions your network for future growth and efficiency.

• Backward Compatibility: If you need to integrate with existing 100G or 200G optical modules, QSFP-DD is the best option. It is specifically designed for environments where maintaining backward compatibility and maximizing port density are critical. Its compact form factor allows for more ports in the same space, making it particularly suitable for data centers with limited space.
• Future Scalability: OSFP is the most future-proof choice, designed to support higher data rates and greater power consumption. It’s perfect for applications requiring advanced thermal management, and it offers the flexibility to scale up to 800Gb/s speeds in the future.
• 400G QSFP112: Offering an excellent balance of high performance, energy efficiency, and compatibility, QSFP112 is ideal for data centers, high-performance computing (HPC) environments, and telecom networks. It enables infrastructure upgrades while maintaining compatibility with existing systems, making it a solid choice for future-proofing your network

• Inter-Data Center or Building-to-Building Connections：consider the VR4,SR4,DR4 or FR4 modules. These options are tailored for inter-data center connections, ensuring your data flows smoothly and efficiently.
• Metropolitan Area Networks and Medium to Long-Range Connections: For connections spanning up to 10 kilometers, LR4 or LR8 modules are perfect. They provide the necessary bandwidth and distance, making them ideal for metropolitan area networks and medium-range applications.
• Wide-Area Networks or Long-Distance Connections: If you need to cover extensive distances—up, up to 40 kilometers—look, no further than the ER4, ER8 module. This option is designed for long-distance connections, ensuring your network remains robust and reliable over greater spans.
• For more: Decoding 400G Optical Modules: How to Choose Between VR4, SR4, SR8, DR4, FR4, LR4, LR8, and ER4?

What 400G modules are available in Asterfusion?