The main difference between QSFP28 and SFP56 is in their form factor and data transfer capabilities.

QSFP28 (Quad Small Form-factor Pluggable 28) is a high-density, hot-pluggable transceiver module used for networking and telecommunication applications. It supports data rates of up to 100 Gbps per port and uses four lanes of high-speed electrical signals.

SFP56 (Small Form-factor Pluggable 56) is also a hot-pluggable transceiver module, but it supports data rates of up to 56 Gbps per port. It is designed for high-speed networking and data center applications, and it uses a higher speed electrical interface compared to previous SFP modules.

In summary, QSFP28 and SFP56 differ in their form factor and supported data rates, with QSFP28 supporting higher data rates and having a larger form factor compared to SFP56.

The size of the optical module will have a greater impact on the construction of the forwarding network. If the module can be made smaller for the same transmission rate, more modules can be installed on a single board of the same size. This increases the single board transmission rate and can also be considered as a smaller board size needed to achieve the same single board rate, which helps to reduce the device size.

Table 1 shows the size and cost of QSFP28 and SFP56 and power consumption at 50G transmission, as can be seen from the table, without taking into account the impact of the module length pull ring on the laying of the premise that.

Table 1. Size and cost of QSFP28 and SFP56 and power consumption at 50G transmission

(1) The number of SFP56 packaged optical modules that can be laid on a single board of the same size is 1.68 times greater than the number of QSFP28 packaged optical modules that can be laid.

(2) The power consumption of a single SFP56 50G 40 km optical module is 57.9% of that of a QSFP28 50G 10 km optical module.

(3) The cost of a single SFP56 50G 40 km optical module is 213.88% of that of a QSFP28 50G 10 km optical module.

It can be concluded that laying SFP56 50G 40 km optical module on the same size single board compared with laying QSFP28 50G 10 km optical module, the power consumption is basically the same, but the single board rate is increased by 1.68 times, or achieving the same single board transmission rate, the single board area is reduced by 40.5% and the power consumption is reduced by 42.1%.

The cost of a conventional QSFP28 50G 10 km C-Temp (0 to 70 °C) optical module is about $180/pcs, and the cost of the SFP56 50G 40 km I-Temp (-40 to 85 °C) optical module in this design is about $385/pcs, so the cost of an SFP56 package optical module is only 26.6% of that of a QSFP28 package for the same distance and at the same transmission rate. The cost is only 26.6% of QSFP28 package.