400G SR4 vs. DR4 InfiniBand Transceivers: A High-Speed Networking Guide
Apr 20, 20251 min read
As data centers evolve to support AI, HPC, and hyperscale workloads, 400G optical transceivers have become critical for high-speed connectivity. Among these, 400G SR4 and DR4 InfiniBand transceivers stand out for their unique capabilities. This guide explores the key features, differences, and applications between 400G SR4 and 400G DR4 InfiniBand modules to help you make an informed decision for your networking needs.
What Are the 400G SR4 and 400G DR4 InfiniBand Transceivers?
Definition
In general, letters often stand for reach or optics technology, and the number denotes the quantity of optical channels:
400G SR4 InfiniBand transceivers are designed for short-reach, high-speed optical communication over multimode fiber (MMF). "SR" stands for "Short Reach," supporting a maximum transmission distance of 50 meters, while "4" indicates four independent 100G optical channels.
Similarly, the 400G DR4 InfiniBand transceivers are a high-speed optical module designed for 400Gbps data transmission. "DR4" denotes a reach of up to 500 meters over parallel single-mode fiber (SMF), with "4" representing four optical channels. 400G SR4 and DR4 transceivers are widely deployed in AI clusters, data centers, and high-performance computing environments where the high-quality 400G/800G NDR connectivity is required.
PAM4 Modulation
Both 400G SR4 and 400G DR4 transceivers utilize PAM4 modulation for their electrical and optical interfaces. Each of the four optical channels is transmitted over separate fibers, operating at 100Gbps per channel. This results in a total of four fiber pairs, achieving an aggregated data rate of 400Gbps. This high-speed transmission capability makes them ideal for bandwidth-intensive applications.
Transmission Distances
In terms of transmission distance, 400G SR4 transceivers support up to 30 meters over OM3 MMF and 50 meters over OM4 MMF, while 400G DR4 transceivers extend up to 500 meters over OS2 SMF.
MPO-12 APC Connectors
To reduce optical back reflection, both 400G SR4 and 400G DR4 transceivers use MPO-12 APC (Angled Physical Contact) connectors, which link to four fiber pairs. It is important to note that older 40G and 100G MMF transceivers, such as the QSFP-100G-SR4, use MPO-12 PC/UPC (un-angled) connectors. For proper compatibility, 400G SR4 and DR4 transceivers must be used with MPO-12 APC connectors. While MPO-12 cables contain 12 fibers, only 8 fibers are utilized — 4 for transmission and 4 for reception. This fiber configuration applies to both 400G SR4 and 400G DR4 modules. An image and drawing of the MPO-12 connector are shown below:
FS 400G SR4 and 400G DR4 InfiniBand Modules: Features & Application
FS 400G InfiniBand transceivers undergo a rigorous series of tests to ensure superior quality and high performance. To guarantee 100% compatibility, every 400G InfiniBand module is tested by the original before shipment. In addition to compatibility testing, the modules undergo spectrum analysis, eye diagram, Bit Error Rate (BER), and temperature testing. These stringent quality control measures ensure that FS transceivers deliver exceptional reliability and performance across diverse operating environments while meeting industry standards.
Two Form Factors: OSFP Flat top and QSFP112
400G SR4 and 400G DR4 InfiniBand transceivers are available in two form factors: QSFP112 and OSFP flat top. The QSFP112 form factors feature a compact design, making them ideal for high-density deployments, while OSFP form factors incorporate advanced cooling mechanisms to support high-power applications. The OSFP version has the same internal design as the QSFP112 module, with the only difference being the connector shell. Please see the table below to see the similarities and differences.
Specification | 400G SR4 InfiniBand Module | 400G DR4 InfiniBand Module | ||
Connector | MPO-12 APC | |||
Max Power Consumption | 8.5W | 9W | 10W | |
Max Distance | 30m@OM3/50m@OM4 or OM5 | 30m@OM3/50m@OM4 | 500m@OS2 | |
Wavelength | 850nm | 1310nm | ||
Modulation (Electrical) | 4x100G-PAM4 | |||
Modulation (Optical) | 4x100G-PAM4 | |||
Technology | InfiniBand & Ethernet | |||
Inbuilt FEC | Yes | Yes | Yes | No |
Transmitter Type | VCSEL | VCSEL | DFB | EML |
Application | Flat-top OSFP for ConnectX-7 Adapter Support Configuration at 1/2 speed for 200G (2x 100G) 800G-to-two 400G Links 800G-to-four 200G Links | QSFP112 for NVIDIA ConnectX-7 Adapters and BlueField-3 DPUs Support Configuration at 1/2 speed for 200G (2x 100G) 800G-to-two 400G Links 800G-to-four 200G Links | Flat-top OSFP for ConnectX-7 Adapter 800G-to-two 400G Links | QSFP112 for NVIDIA ConnectX-7 Adapters and BlueField-3 DPUs Support Configuration at 1/2 speed for 200G (2x 100G) 800G-to-two 400G Links 800G-to-four 200G Links |
400G InfiniBand SR4 Modules Applications
The 400G InfiniBand SR4 modules provide flexible breakout configurations, enhancing network scalability and adaptability. They can connect to the twin-port 800G NDR OSFP finned-top SR8 module, facilitating seamless integration between 800G NDR switch and a combination of 400G ConnectX-7 adapters or BlueField-3 DPUs. Additionally, 400G SR4 transceivers support 1/2-speed configurations for 200G. When connected to a 1:2 splitter fiber cable, where the split end has only two active channels, the 400G transceiver automatically activates only two channels, operating at 200G speed while reducing power consumption. This functionality simplifies the transition from 200G to 800G networks.
800G SR8 to 2x 400G SR4 Links to ConnectX-7 and/or BlueFieId-3 DPUs
800G SR8 to 4x 200G SR4 Links to ConnectX-7 and/or BlueField-3 DPUs
400G InfiniBand DR4 Modules Applications
Similar to 400G SR4 modules, two 400G DR4 modules can connect to an OSFP-DR8-800G finned top module by using two MPO-12/APC OS2 fiber cables, enabling seamless connectivity between 800G NDR switches and 400G ConnectX-7 or BlueField-3 DPUs. Unlike 400G SR4 modules, which has a maximum reach of 50m, 400G DR4 modules extends up to 500m. Additionally, FS currently only the QSFP112-DR4-400G module supports downshifting to 200G speeds, allowing for an 800G to 4x 200G breakout, simplifying the transition from 200G to 800G networks.
800G DR8 to 2x 400G DR4 Links to ConnectX-7 and/or BlueFieId-3 DPUs
800G to 4x 200G DR4 Links to ConnectX-7 and/or BlueField-3 DPUs
Choosing Between 400G SR4 and DR4 InfiniBand Modules
When choosing between the 400G SR4 and 400G DR4 InfiniBand modules, please consider the following factors:
Protocol Considerations
FS 400G SR4 and DR4 transceivers support both InfiniBand and Ethernet, ensuring broad compatibility across different network infrastructures. When selecting a module, verify its compatibility with your existing network equipment and protocols.
Application Scenarios
400G SR4 transceivers: Designed for short-reach data center interconnects, typically used for connections within racks.
400G DR4 transceivers: Supports transmission distances up to 500m, making it ideal for switch-to-server connectivity in larger-scale deployments.
Economic Considerations
400G SR4 transceivers: More cost-effective due to the lower price of multimode fiber (MMF), making them a budget-friendly choice for short-distance applications.
400G DR4 transceivers: Require higher-cost single-mode fiber (SMF) but provide extended reach and better scalability for high-speed networking.
OSFP vs. QSFP112
Besides choosing between 400G SR4 and 400G DR4 modules, it is also important to select the appropriate form factor. OSFP and QSFP112 are two physically different form factors. Ensure your device supports the selected form factor to avoid installation or performance issues.
FAQs
Q1: Does FS provide InfiniBand modules with a longer distance than 500M?
A: Yes, FS offers not only InfiniBand modules with a 500M range but also 400G InfiniBand modules (QSFP112-XDR4-400G and QSFP112-FR4-400G) that support medium to long-range transmission, with a maximum reach of up to 2km, catering to various high-performance network needs.
Q2: What are the main differences between OSFP and QSFP112 packages?
A: The main differences lie in compatibility and scalability. OSFP flat-top only connects to ConnectX-7 adapters. The OSFP flat-top module only connects to ConnectX-7 adapters due to its larger size and higher power requirements, while QSFP112 can connect to both ConnectX-7 adapters and BlueField-3 DPUs. Additionally, QSFP112 is designed for 112G SerDes and offers backward compatibility with existing QSFP ports. Since 800G NDR and 1.6T XDR switches use the OSFP form factor, choosing OSFP modules may better support future scalability.
Q3: Does FS offer other products or solutions besides the 400G SR4 and 400G DR4 InfiniBand modules?
A: Absolutely! You can check our H100 InfiniBand solution to find more details. Contact our solution experts for custom network upgrades tailored to your needs — from 400G optics to AI cluster optimizations.