Upgrading Data Center Networks from 100G to 400G Utilizing Multimode Fiber
Updated at Jul 1st 20241 min read
Ongoing Evolution of Data Center Networks
The continuous evolution of data center networks encompasses two crucial aspects. Firstly, they must accommodate the escalating demands for bandwidth and traffic generated by data-intensive applications like artificial intelligence, machine learning, and IoT. These applications are already pushing the limits of existing 10G and 40G links. Secondly, data centers need to prioritize power efficiency to address the growing need for sustainability.
By adopting 400G optical transceivers, data center networks can effectively address both requirements. Remarkably, these upgrades can be achieved without making any alterations to the existing multimode fiber infrastructure. Multimode fiber offers cost-effective support for higher speeds over shorter distances, making it an ideal choice for switch-to-switch and switch-to-server configurations.
Building 4x 100G breakout networks using 400G DR4 optics over single-mode fiber is relatively easy. However, when it comes to multi-mode fiber, it’s not as easy to do. Although 400G SR8 exists, it’s not suitable for building 4x 100G breakout networks. But fear not, because the 400G SR4.2 optic is here to save the day!
The 400G SR4.2 optical transceiver pairing with 100G SR1.2 optics is the ultimate solution for building 4x 100G breakout networks over multi-mode fiber. This powerful combination facilitates migration from 4x 10G or 4x 25G to 4x 100G over multi-mode fiber, offering both an upgrade and a way to preserve existing fiber infrastructure investments.

Advantages of FS QSFP28 100G SR1.2 and QSFP-DD 400G SR4.2
FS, a reputable provider of optical transceiver solutions, offers a variety of modules including the QSFP28 100G SR1.2 and QSFP-DD 400G SR4.2. These products come with significant advantages that set them apart in the market. FS QSFP28 100G SR1.2 optical transceivers facilitate the upgrade to 100G by utilizing the current bidirectional duplex fiber. The FS QSFP-DD 400G SR4.2 optical transceivers support the shift to 400G with either bidirectional duplex or SR4 quad fiber. Both types simplify the migration to higher speeds, maintain existing fiber infrastructure and investments, and offer enhanced power efficiency and sustainability. The following are key advantages of them.
Built-in well-known Broadcom or Inphi DSP chip, low power consumption.
Tested in targeted switches for superior performance, quality, and reliability.
Support FS BOX real-time configuration.
Stay ahead of surging traffic demands with flexible paths to 400G.
Safeguard existing investments in multimode fiber infrastructure.
Leverage breakout capabilities and high-density links to connect 400G and 100G ports.
Capitalize on the latest high-speed platforms and features.
Enhance power efficiency and sustainability within data center networks.

How to Upgrade Data Center Networks from 100G to 400G?
1. Upgrade Leveraging Bidirectional Duplex Fiber
FS's QSFP28 100G SR1.2 and QSFP-DD 400G SR4.2 optical transceivers can effectively utilize existing bidirectional duplex fiber during the migration to higher speeds. These transceivers offer interoperability, enabling a gradual transition from 100G to 400G. The 400G SR4.2 employs 4 pairs (optical lanes) of multi-mode fiber, with each pair transmitting and receiving 50G optical signals simultaneously at 850nm and 910nm wavelengths, resulting in an aggregated data rate of 100G per pair (optical lane). Similarly, the 100G SR1.2 utilizes one pair (optical lane) of multi-mode fiber, operating bi-directionally with the same wavelength combination. Additionally, FS's QSFP-DD SR4.2 transceivers support breakout connectivity to QSFP28 100G SR1.2, facilitating the upgrade of one end of the links to 400G ports while maintaining high-density links to 100G ports at the other end.

2. Upgrade Utilizing SR4 Quad Fiber
In addition to using bidirectional duplex fiber, QSFP-DD 400G SR4.2 optical transceivers can also leverage existing SR4 quad fiber for their operations. This capability provides data center teams with the flexibility to deploy 400G connectivity within the network spine or across both spine and leaf architectures. By doing so, they can effectively scale their network infrastructures while preserving their substantial investments in the existing SR4 fiber and related infrastructure. This not only enhances the efficiency and cost-effectiveness of the network expansion but also ensures that the already established investments in SR4 fiber resources are fully utilized, offering a seamless upgrade path without the need for a complete overhaul of the existing cabling systems.
Boost Data Center Networks with 400G
The migration to 400G not only boosts network bandwidth and performance but also enhances data center efficiency and sustainability. New 400G platforms, leveraging 112G SerDes technology and Silicon One, offer exceptional density, reduced power consumption per bit, and improved optical power efficiencies. These advancements result in enhanced power and cooling efficiency within data centers.
Product Lists
FS 100GBASE-SR1.2 QSFP28 transceiver is used for short-reach data communication and interconnect applications. It offers customers a compelling solution that enables reuse of their existing 10Gb duplex MMF infrastructure for migration to 100 Gigabit Ethernet connectivity. This transceiver is compliant with the QSFP28 MSA and IEEE 802.3bm CAUI-4 electrical interface. It can also connect to a 400Gbps SR4.2 BiDi in a 4x 100G-SR1.2 breakout mode. The 400GBASE-SR4.2 module, MTP/MPO-12 connector, up to 150m over parallel OM5 multi-mode fiber. It is compliant with the IEEE 802.3 protocol and 400GAUI-8/PAM4 standard. The built-in digital diagnostics monitoring (DDM) allows access to real-time operating parameters. It is suitable for 400G ethernet and data center interconnect applications. And it can support 4x 100G-SR1.2.
Center Wavelength | 850nm, 910nm | 850nm, 910nm |
Connector | Duplex LC | MTP/MPO-12 |
Cable Distance (Max.) | 70m@OM3/100m@OM4/150m@OM5 | 70m@OM3/150m@OM5 |
Modulation | 2x 50G PAM4 | 8x 53.125G PAM4 |
DSP | / | Inphi DSP |
Power Consumption | ≤4W | ≤12W |
Transmitter Type | Marvell VCSEL | VCSEL |
Packaging Technology | / | COB |
Application | Data Center100GBASE Ethernet | Data Center400G to 4x 100G Breakout |
To learn more about FS QSFP-DD 400G SR4.2 and QSFP28 100G SR1.2 optical modules, and to explore FS Optical Transceivers' comprehensive product information, please visit FS.com.