No, QSFP+ (Quad Small Form-Factor Pluggable Plus) optics cannot be plugged directly into the port of QSFP28 (Quad Small Form-Factor Pluggable 28). The two form factors are designed for different data rates, and there are electrical and mechanical differences between them. 

1. Data Rates:

• QSFP+: QSFP+ supports data rates up to 40 Gbps per port.

• QSFP28: QSFP28 supports higher data rates, typically up to 100 Gbps per port.

2. Electrical and Mechanical Differences:

• QSFP+ and QSFP28 have different electrical and mechanical designs. The connectors are not physically compatible due to the differences in their form factors and specifications.

3. Backward Compatibility:

• While the QSFP28 form factor supports higher data rates, it is typically backward compatible with QSFP+. This means that a QSFP28 port can often accept QSFP+ optics, but not the other way around.

4. Compatibility Considerations:

• When using backward compatibility, the overall data rate will be limited to the capabilities of the QSFP+ optics. For example, if you insert a QSFP+ optic into a QSFP28 port, the link will operate at the maximum data rate supported by the QSFP+ optic (e.g., 40 Gbps).

It's essential to check the specifications and compatibility of your networking equipment and optics to ensure proper functionality. Always refer to the documentation provided by the equipment manufacturer for accurate information on supported module types and form factors. If you need higher data rates, consider using optics designed for the QSFP28 port rather than trying to use QSFP+ optics on a QSFP28 port.