Difference between QSFP56 vs QSFP28 vs QSFP+

The 200G QSFP56 optical module and the 200G QSFP-DD optical module are two mainstream solutions for 200G optical interconnects. The QSFP56 utilises mainstream digital signal processors (DSPs) to help cloud data centres meet the tough challenges of achieving more efficient optical interconnects at a flexible and scalable scale and low cost. This article will introduce you to the optical module 200G QSFP56 package technology and the difference between the QSFP56 package and the QSFP28 and QSFP+ packages.

Overview of 200G QSFP56 optical module packaging technology

The 200G QSFP56 optical module is an upgraded version of the 40G QSFP+ and 100G QSFP28 optical modules and is designed specifically for 200G Ethernet interconnects. modules. Depending on the transmission distance, 200G QSFP56 optical modules are divided into QSFP56 CR, SR, DR, FR and LR, which can be used for different distances on single-mode and multimode fibres.

 200G QSFP56

In general, two 200G QSFP56 optical modules can be plugged into the corresponding switch port and connected with a single-mode or multimode fibre to achieve a 200G transmission rate. In addition, 200G transmission can also be achieved by inserting a QSFP56 DAC/AOC high-speed cable into the corresponding port. For 2x100G or 4x50G transmission, 200G QSFP56 to 2x100G QSFP28 branch cables and 200G QSFP56 to 4x50G SFP56 branch cables can be used to achieve this.

Difference between QSFP56 vs QSFP28 vs QSFP+

By name, QSFP56, QSFP28 and QSFP+ optical modules have the same package type, but they have different transmission rates, modulation techniques, interfaces, etc.

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 100GBASE-QSFP28-CWDM4-10km Optical Transceiver Module      

The QSFP56 package type can support 4x50G transmission to achieve a 200G transmission rate, while the QSFP+ module is an upgraded version of the QSFP module and can support 4x10G transmission for 10G Ethernet, 10G Fibre Channel and QDR InfiniBand. It can multiplex four channels to increase bandwidth and achieve 40Gbps transmission rates (10GBaud NRZ per channel). QSFP28 optical modules, like QSFP+ optical modules, contain 4 optical transmitters and 4 optical receivers to support 4x25G transmission, resulting in 100G transmission rates.

The main difference between the QSFP56 package and the QSFP+ and QSFP28 packages is that the QSFP56 no longer adopts the previous NRZ modulation technology, but instead adopts PAM4 modulation technology, which can achieve transmission rates of up to 50G per channel, allowing more data to be transmitted over existing fibre, making it more suitable for applications in hyperscale data centre networks.

 40GBASE-QSFP+-PSM LR4-10km Optical Transceiver Module

200G QSFP56 to 400G QSFP-DD

With the rapid growth of data centres, the demand for data transmission is also increasing, driving the network towards higher bandwidth and higher density. There is now a new generation of 400G optical module packages on the market - the 400G QSFP-DD, where "DD" refers to dual-density, meaning that the number of channels in the 400G QSFP-DD has changed from four to eight, allowing for 400G transmission rates. This means that the number of channels in the 400G QSFP-DD has been changed from 4 to 8, enabling 400G transmission rates to be achieved.

The 400G QSFP-DD optical module is similar in size to the 200G QSFP56 optical module, but the 400G QSFP-DD optical module is backwards compatible with 40G QSFP+, 100G QSFP28, 200G QSFP56 and other QSFP packaged optical modules. This means that 200G QSFP56 optical modules can work on 400G QSFP-DD ports as long as the switch supports them. When using a 200G QSFP56 optical module on a 400G QSFP-DD port, the switch's port will be configured for a 200G transmission rate instead of 400G.

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