The QSFP28 (Quad Small Form-Factor Pluggable 28) is a high-speed transceiver module widely used in data center and telecommunications applications to support data rates of 100 Gigabits per second (Gbps). The specifications for QSFP28 are defined by industry standards, primarily by the Multi-Source Agreement (MSA) group, which establishes the mechanical, electrical, and optical characteristics of the module. Here are the key standard specifications for QSFP28:

1. Form Factor:

• QSFP28 is a hot-pluggable transceiver module with a small form factor. It is designed to be compatible with QSFP and QSFP+ ports.

2. Electrical Interface:

• The electrical interface of QSFP28 supports four independent channels, allowing for data rates of 25 Gbps per channel (4 x 25 Gbps = 100 Gbps).

3. Optical Connectivity:

• QSFP28 modules are available for both optical and copper connectivity.

• For optical connections, QSFP28 supports various standards like SR4 (Short Range 4 lanes), LR4 (Long Range 4 lanes), and ER4 (Extended Range 4 lanes), among others.

4. Copper Connectivity:

• QSFP28 modules can support direct attach copper (DAC) connections for short-distance applications within a data center.

5. Modulation:

• QSFP28 uses advanced modulation schemes to achieve higher data rates, such as PAM4 (Pulse Amplitude Modulation 4).

6. Maximum Reach:

• The reach or distance that QSFP28 modules can support depends on the specific standard and application. For example, SR4 modules are designed for shorter distances within a data center, while LR4 modules are suitable for longer-range connections.

7. Wavelength:

• In optical modules, QSFP28 uses specific wavelengths depending on the application (e.g., 850nm for SR4, 1310nm for LR4).

8. MSA Compliance:

• QSFP28 modules comply with the Multi-Source Agreement (MSA) standards, ensuring interoperability among different vendors' products.

It's important to note that QSFP28 is just one of the form factors available in the QSFP family. There are newer form factors like QSFP56 and QSFP-DD designed to support even higher data rates (e.g., 200 Gbps, 400 Gbps). When deploying QSFP28 modules, it's advisable to consult the specific datasheets and documentation provided by the module manufacturer for detailed specifications and compatibility information.