QSFP28 and QSFP+ are both types of transceiver modules used in high-speed networking applications, but there are some key differences between the two.

1.Data Rate: QSFP28 supports data rates of up to 100 Gbps, while QSFP+ supports data rates of up to 40 Gbps. 

2. Number of Lanes: QSFP28 uses four lanes for data transmission, while QSFP+ uses either four lanes for 40 Gbps or 10 lanes for 100 Gbps.

3. Power Consumption: QSFP28 typically has lower power consumption compared to QSFP+ at the same data rate.What is the maximum length of QSFP？

4. Distance: QSFP28 can typically transmit data over longer distances compared to QSFP+ at the same data rate.

5. Compatibility: QSFP28 transceivers are not backward compatible with QSFP+ ports, so a QSFP28 transceiver cannot be used in a QSFP+ port. However, QSFP+ transceivers can be used in QSFP28 ports at reduced data rates.

Overall, QSFP28 provides higher data rates, lower power consumption, and longer transmission distances compared to QSFP+, making it suitable for high-performance networking applications.