The word SFP is an IT industry term which stands for Small Form Factor Pluggable. An SFP is a variety of Optical Transceiver, which is designed to convert serial electric signals into serial optical signals. SFP modules are typically inserted into a network switch in order to connect a Fiber Optic system with an Ethernet system. The most common applications where SFP modules are used include Fibre Channel and Gigabit Ethernet.

Industry specifications for the SFP transceiver have been standardized by an agreement called the MSA or Multi Source Agreement between competing manufacturers. The MSA guarantees inter-compatibility between vendor products. The SFP was designed as a predecessor to the GBIC interface, and supports a greater number of transceivers per inch than the GBIC, which is why the SFP is also known as Mini GBIC.

SFP transceivers can be acquired with a variety of receiver and transmitter types. Users can choose the appropriate SFP transceiver for each Fiber Optic link they are deploying to provide the required reach depending on the type of optical fiber they are using (i.e Multi Mode or Single Mode Fiber). SFP transceivers are available in several different categories including 850 nm 550m MMF (SX), 1310 nm 10 km SMF (LX), 80 km (ZX), 120 km (EX or EZX), CWDM and DWDM. SFP transceivers are also available with a copper cable interface to connect to unshielded twisted pair networking cable.

The Cisco 1000BASE-T SFP for Copper networks, such as the GLC-T, operates on standard Category 5 unshielded twisted pair copper cabling of up to 100m (328 ft) link length. Cisco 1000BASE-T SFP modules support 10/100/1000 autonegotiation and Auto MDI/MDIX.

The Cisco 1000BASE-SX SFP for Multimode Fiber Only, such as the GLC-SX-MM, are compatible with the IEEE 802.3z 1000BASE-SX standard, operates on legacy 50 ¼m multimode fiber links up to 550 m and on 62.5 ¼m Fiber Distributed Data Interface (FDDI)-grade multimode fibers up to 220 m. It can support up to 1km over laser-optimized 50 ¼m multimode fiber cable.

Cisco 1000BASE-LX/LH SFP for Both Multimode and Single-Mode Fibers, such as the GLC-LH-SM, are compatible with the IEEE 802.3z 1000BASE-LX standard, operates on standard single-mode fiber-optic link spans of up to 10 km and up to 550 m on any multimode fibers.

Cisco 1000BASE-EX SFP for Long-Reach Single-Mode Fibers, such as the GLC-EX-SMD, operate on standard single-mode fiber-optic link spans of up to 40 km in length. A 5-dB inline optical attenuator should be inserted between the fiber-optic cable and the receiving port on the SFP at each end of the link for back-to-back connectivity.

Cisco 1000BASE-ZX SFP for Long-Reach Single-Mode Fibers, such as the GLC-ZX-SM, operate on standard single-mode fiber-optic link spans of up to approximately 70 km in length. The SFP provides an optical link budget of 23 dB, but the precise link span length depends on multiple factors such as fiber quality, number of splices, and connectors.

Cisco 1000BASE-BX10-D and 1000BASE-BX10-U SFP for Single-Fiber Bidirectional Applications are compatible with the IEEE 802.3ah 1000BASE-BX10-D and 1000BASE-BX10-U standards, operate on a single strand of standard SMF.