SFP Transceivers: SFP, SFP+, SFP28 - What are the Differences?

What is an SFP transceiver?

There are a range of SFP transceivers available on the market. In this article, we take a look at the differences between them and various applications that they are used in within networking environments.

What does SFP stand for?

The acronym SFP stands for Small Form Factor Pluggable, and transceivers which were developed following the SFP Multi-Source Agreement are compact hot-pluggable modules which enable easy connection and data transfer via copper or fiber cables to and from a large range of networking devices. As they are able to connect a network device to a wide variety of cable types (Ethernet, single-mode or multi-mode optical fiber), and are flexible to use when network modifications are required, SFP modules are the most popular of all optical transceiver formats.

Since the first SFP form factor was launched, there have been upgrades to account for the unrelenting demand for higher bandwidth and increased data rates, leading to development of the SFP+, SFP28, SFP56 and SFP-DD (not forgetting the QSFP) modules.

SFP transceivers history

SFP (Small Form-factor Pluggable) transceivers were launched in 2002, about 5 years after GBIC, as a smaller ”mini” version, achieving typical speeds of 1 Gbps for Ethernet and 4Gbps for Fibre Channel. SFP modules are still sometimes referred to as ”mini GBIC”. In 2006 the SFP+ (Enhanced Small Form-factor Pluggable) was launched, with speeds of up to 10 Gbps. SFP+ is still a dominant industry format today, with data transmission available up to 16 Gbps. The SFP and SFP+ have the same physical dimensions, and were followed by SFP28 in 2014, which was designed to bring speeds up to 25 Gbps.

1000M SFP Copper
100 m, SERDES, RJ45

Selecting an SFP Module

There are a wide variety of SFP transceivers, which can be selected based on the cable type (copper or fiber optical) they support alongside the transmission range and speed of transfer, single-mode and multi-mode optical fiber for different applications.

SFP for Gigabit Ethernet

Copper-based SFP modules using Gigabit Ethernet (1000BASE-T and 1000BASE-TXI) networking have a range of up to 100 meters.

Fiber Optical SFP, SFP+, SFP28/SFP56 and SFP-DD Modules

Fiber optical SFP modules can handle distances of up to 160km from 10 Mbps to 1Gbps, with connectors for LC Duplex, LC Simplex, SC Simplex. The most common optical modules use the 850nm wavelength to transmit to a maximum of 550 meters with multi-mode fiber. Single-mode SFP modules transmitting at 1310nm wavelength can reach a maximum of 20km.

10G SFP+ LR
10 km, 1310 nm, DDM,
LC Duplex, Singlemode

SFP+ transceivers transmit at distances from 30 meters to 120 kilometers at a data rates of 8 Gbps, 10 Gbps and 16 Gbps. SFP+ modules connector types cover LC Duplex and LC Simplex.

SFP28 modules can reach distances between 100 meters and 40 kilometers, transmitting at 25 Gbps. SFP28 modules are available for single and multi-mode fiber (LC Simplex and LC Duplex) connections.

SFP56 – Compatible with the previous SFP and SFP28 modules, the SFP56 pluggable transceiver, enables transmission from 100m to 10 km at up to 50G, providing even faster bandwidth for data centers.

SFP-DD – Small Form-factor Pluggable Double Density) is one of the latest standards released by the MSA Group. It enables data centers to increase data rates with 50G transmitted over 2 channels providing an overall signaling rate of 100G and supporting distances of between 500m and 10km. SFP-DD is also compatible with SFP+ modules and cables. The standard will also be supporting a data rate of 200G over two channels using PAM4.

Are SFP and SFP+ modules interchangeable?

SFP optical transceivers can be used in SFP+ ports from some suppliers (such as Cisco), however, the data rate will be reduced to the level of the SFP module, for example, down to 1 Gbps, rather than 10 Gbps. SFP+ modules can be used in SFP ports but the data rate will then lower to the maximum that the port supports.

Where different types of SFP modules are used

There are a range of SFP transceivers adapted for different applications, from simplex SFP modules for single fiber applications to SFP modules for long-reach WDM (Wavelength Division Multiplexing), tunable modules and ones further adapted to withstand exacting operating temperatures, for example.

1000M SFP SWDM ZX+
120 km, nm, DDM,
LC Duplex, Singlemode

Long-range WDM (Wavelength Division Multiplexing)

Wavelength Division Multiplexing (WDM) enables the transmission of multiple signals simultaneously over a single fiber. CWDM and DWDM SFP modules are used for long haul and metro networks, for example, where there is a need to maximise the number of services delivered over fiber at long distances. SFP CWDM & DWDM modules have a range of between 40 – 160 km, with SFP+ ranging from 40 to 100 km. WDM is also being used by enterprises, datacenters and government operators as a cost-effective solution.