The Quad Small Form-factor Pluggable (QSFP) is a compact, hot-pluggable transceiver used for data communications applications. The form factor and electrical interface are specified by a multi-source agreement (MSA) under the auspices of the Small Form Factor Committee. It interfaces networking hardware (such as servers and switches) to a fiber optic cable or active or passive electrical copper connection. It is an industry format jointly developed and supported by many network component vendors, allowing data rates from 4x1 Gb/s for QSFP and 4x10 Gbit/s for QSFP+ and to the highest rate of 4x28 Gbit/s known as QSFP28 used for 100 Gbit/s links.

QSFP transceivers are available with a variety of transmitter and receiver types, allowing users to select the appropriate transceiver for each link to provide the required optical reach over multi-mode or single-mode fiber. QSFP modules are commonly available in several different categories:

• 4 x 1 Gbit/s QSFP

• The original QSFP document specified four channels carrying Gigabit Ethernet, 4GFC (FiberChannel), or DDR InfiniBand.

• 4 x 10 Gbit/s QSFP+

• QSFP+ is an evolution of QSFP to support four 10 Gbit/sec channels carrying 10 Gigabit Ethernet, 10GFC FiberChannel, or QDR InfiniBand. The 4 channels can also be combined into a single 40 Gigabit Ethernet link.

• 4 x 14 Gbit/s QSFP+ (QSFP14)

• The QSFP14 standard is designed to carry FDR InfiniBand, SAS-3. or 16G Fibre Channel

• 4 x 28 Gbit/s QSFP+ (QSFP28)

• The QSFP28 standard is designed to carry 100 Gigabit Ethernet, EDR InfiniBand. or 32G Fibre Channel. This transceiver type is also used with direct-attach breakout cables to adapt a single 100GbE port to four independent 25 gigabit ethernet ports (QSFP28-to-4x-SFP28). Sometimes this transceiver type is also referred to as "QSFP100" or "100G QSFP" for sake of simplicity.

• QSFP has 38 pins including 4 high-speed TX pairs (CML-I) and 4 high-speed RX pairs (CML-O).