QSFP56 vs. QSFP28 Transceivers: Which One should You Choose?

Both QSFP28 and QSFP56 belong to the QSFP packaging family and use the same form factor.  Therefore, they are compatible in terms of physical size and interface, meeting the requirements for small size, low power consumption, and hot-swappable operation. Their true differences lie in their internal functional parameters, which give them different performance characteristics and make them suitable for different application environments.

Comparison of Core Parameters of QSFP28 and QSFP56

QSFP28 (Quad Small Form-factor Pluggable 28) is a compact, hot-pluggable optical module package used for 100Gbps high-speed networks. It transmits data through four channels, each at a rate of 25Gbps (<4x25G) or 28Gbps (actual electrical interface), achieving a total bandwidth of 100Gbps.  It is mainly used in data centers and 5G networks, enabling low power consumption and high-density connectivity. It supports various application scenarios from short-range (SR4) to long-range (LR4, ER4) and is compatible with most 100G network equipment on the market, making it the standard choice for 100G networks in data centers over the past few years.

QSFP56 (Quad Small Form-factor Pluggable 56) is an upgraded version of QSFP28, utilizing PAM4 modulation technology and incorporating a DSP (Digital Signal Processing) chip. The single-channel rate is doubled to 56Gbps, and the total rate supported by the four channels reaches 200Gbps. It is mainly used in 200G Ethernet and InfiniBand HDR, achieving higher density per unit. Like QSFP28, QSFP56 also supports various application scenarios from short-range (SR4) to long-range (LR4, ER4) and is also commonly used in data centers, but it has become a marginal player in the era of 400G and 800G.

Power Consumption of QSFP28 and QSFP56

QSFP28 has very low power consumption, typically around 3.5W-4.5W. Even long-distance modules (80KM) do not exceed 5W. This makes QSFP28 the preferred choice for high-density 100G network deployments. Lower power consumption leads to lower operating and maintenance costs, so QSFP28 optical modules have been and continue to be the preferred choice for network construction.

QSFP56 has twice the speed of QSFP28, but this higher speed comes at a cost. The power consumption of QSFP56 modules is typically about 40-70% higher than that of QSFP28, usually in the 6-8W range. This leads to higher power supply and cooling requirements, requiring a reassessment of power distribution, but the performance improvement is not very significant. In practical network construction, engineers tend to increase their budget and directly use 400G and 800G modules to achieve higher bandwidth per unit, thus marginalizing the use of QSFP56.

QSFP28 and QSFP56 Interoperability

Both QSFP28 and QSFP56 belong to the QSFP family of packages, so their physical dimensions are similar, and they are backward compatible. The upgraded QSFP56 is backward compatible with QSFP28, meaning that QSFP28 modules can be used in QSFP56 ports. However, conversely, while QSFP56 modules can be inserted into QSFP28 ports, they will not function properly because QSFP28 ports cannot provide a single-channel rate of 56G. This should be noted during use.

How to Choose Between QSFP28 and QSFP56 Packages

In practical applications, engineers need to consider the specific network bandwidth and future upgrade plans, and choose the appropriate package based on various factors. In 100G networks, choosing the QSFP28 package offers the best economic benefits. For higher-speed networks and the QSFP56 package, engineers usually consider higher-speed 400G and 800G QSFP-DD packages, and QSFP56 is not typically included in their considerations. However, this does not mean that the QSFP56 package is useless. In InfiniBand HDR computing networks, 200G QSFP56 is the absolute main component.  Additionally, in high-speed leaf-spine network architectures, the connection between servers and leaf switches often uses QSFP-DD 400G to QSFP56 200G cables, allowing for rational allocation of network bandwidth and reducing resource waste.

In summary, both QSFP28 and QSFP56 have their advantages and disadvantages. In practical use, the appropriate choice should be made based on specific circumstances. YXFiber provides various QSFP28 and QSFP56 optical modules and cables, making it an ideal choice for your network construction.