This document will focus on QSFP, QSFP+ and QSFP28. Though they look very similar in physical appearance but the transmit data rates are quite different.
QSFP, QSFP+ and QSFP28 transceivers look very similar because they
all share the same small form-factor. The QSFP has evolved to QSFP+ to
10 Gbps data rates. The standard is the SFF-8436. Further demand for higher data rates led to introduction of QSFP28 which supports up to 100 Gbps of speed.
Abbreviation stands for Quad Small Form Factor Pluggable.
QSFP is available for use in both singlemode and multimode and can
support 4 independent channels that can individually transmit at up to
1.25 Gbps per channel for an total speed of above 4 Gbps.
Abbreviation stands for Quad Small Form Factor Pluggable Plus.
QSFP+ supports Ethernet, Fibre Channel and Infiniband at 10Gbp/s per
channel up to a maximum of 4 channels for a total speed of 40Gbp/s.
QSFP28 combines speeds of 28Gbps per channel for a total speed of
100Gbps. The QSFP28 interface is highly flexible and can be used in the
2 X 50 Gbps
4 X 25 Gbps
Usually QSFP28 modules can’t breakout into 10G links. But if a QSFP28
module is inserted into a QSFP+ port, a QSFP28 can break out into 4x10G.