As the digital wave sweeps across the world, network communication technology is changing with each passing day. The speed and stability of data transmission have become the focus of attention for enterprises and data centers. In the actual network construction and upgrade process, it is often necessary to convert 100G QSFP28 to 25G SFP28 to meet the diverse needs of different network architectures. So, how can this conversion be achieved efficiently and reliably? This article will introduce several connection methods from QSFP28 to SFP28.

1. Use The Conversion Module
You can use a dedicated 100G QSFP28 to SFP28 conversion module, such as the CVR-QSFP28-SFP28 conversion module of ETU-Link. Insert the conversion module into the 100G QSFP28 port, and then insert the 25G SFP28 optical module into the SFP28 slot of the conversion module to achieve the conversion from 100G QSFP28 to 25G SFP28. This method is simple and convenient, and is suitable for scenarios that are more sensitive to cost, have low requirements for transmission distance, or have changes in networking.


2. Use ETU-Link High-speed Cable
100G QSFP28 to 4×25G SFP28 DAC high-speed cable: This type of cable is cost-effective and does not require laser optical devices, which can reduce costs compared to other conversion or connection methods. It has obvious advantages in large-scale deployment. It is easy to install and use, does not require complex configuration and additional equipment, and is suitable for short-distance connections, especially within the rack and between adjacent racks (generally within 5 meters). It can perform well, and the number of cables and wiring complexity are low, which is easy to manage and maintain, reducing construction and operation costs.


100G QSFP28 to 4×25G SFP28 AOC active optical cable: one end is a 100G QSFP28 connector, the other end is 4 25G SFP28 connectors, compliant with SFF-8 6 36 and SFF-8431 standards, using 850nm VCSEL laser and PIN photodetector, in OM3 fiber transmission, the maximum link length is 70 meters, while the maximum link length of OM4 transmission is 100 meters.

3. Use Branch Fiber Patch Cords
The 8/12-core MPO-4 * duplex LC branch patch cord connects the 100G QSFP28 optical module with four 25G SFP28 optical modules, which is suitable for short-distance connections and convenient for transforming existing networks. For example, connections within the same rack or cabinet provide a flexible solution for the connection needs of modern data centers.

In summary, there are many ways to convert QSFP28 to SFP28, each with its own unique advantages and applicable scenarios. The QSFP28 conversion module allows the use of an adapter with an SFP28 optical module or cable to connect to a low-speed port at the other end of the network; the 100G QSFP28 to 4x25G SFP28 DAC branch high-speed cable supports a connection distance of 5m within the rack; the 100G QSFP28 to 4x25G SFP28 AOC branch optical cable can cover a distance of 1 - 70m between switches (even up to 100m with OM4 fiber); and the branch optical patch cord can directly connect a 100G QSFP28 optical module to 4 25G SFP28 optical modules.

The detailed differences are shown in the figure below

In practical applications, we need to comprehensively consider multiple factors such as transmission distance, cost budget, and power consumption to select a suitable interconnection solution.