10 Gigabit Ethernet

10 Gigabit Ethernet (10GE, 10GbE, or 10 GigE) is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabits per second. It was first defined by the IEEE 802.3ae-2002 standard. Unlike previous Ethernet standards, 10GbE defines only full-duplex point-to-point links which are generally connected by network switches; shared-medium CSMA/CD operation has not been carried over from the previous generations of Ethernet standards so half-duplex operation and repeater hubs do not exist in 10GbE. The first standard for faster 100 Gigabit Ethernet links was approved in 2010.

The 10GbE standard encompasses a number of different physical layer (PHY) standards. A networking device, such as a switch or a network interface controller may have different PHY types through pluggable PHY modules, such as those based on SFP+. Like previous versions of Ethernet, 10GbE can use either copper or fiber cabling. Maximum distance over copper cable is 100 meters but because of its bandwidth requirements, higher-grade cables are required.

The adoption of 10GbE has been more gradual than previous revisions of Ethernet: in 2007, one million 10GbE ports were shipped, in 2009 two million ports were shipped, and in 2010 over three million ports were shipped, with an estimated nine million ports in 2011. As of 2012, although the price per gigabit of bandwidth for 10GbE was about one-third compared to Gigabit Ethernet, the price per port of 10GbE still hindered more widespread adoption.

By 2022, the price per port of 10GBase-T had dropped to $50 - $100 depending on scale. In 2023, Wi-Fi 7 routers began appearing with 10GbE WAN ports as standard.

Standards

Over the years the Institute of Electrical and Electronics Engineers (IEEE) 802.3 working group has published several standards relating to 10GbE.

Physical layer modules

To implement different 10GbE physical layer standards, many interfaces consist of a standard socket into which different physical (PHY) layer modules may be plugged. PHY modules are not specified in an official standards body but by multi-source agreements (MSAs) that can be negotiated more quickly. Relevant MSAs for 10GbE include XENPAK (and related X2 and XPAK), XFP and SFP+. When choosing a PHY module, a designer considers cost, reach, media type, power consumption, and size (form factor). A single point-to-point link can have different MSA pluggable formats on either end (e.g. XPAK and SFP+) as long as the 10GbE optical or copper port type (e.g. 10GBASE-SR) supported by the pluggable is identical.

XENPAK was the first MSA for 10GE and had the largest form factor. X2 and XPAK were later competing standards with smaller form factors. X2 and XPAK have not been as successful in the market as XENPAK. XFP came after X2 and XPAK and it is also smaller.

The 10 gigabit module standard is the Enhanced Small Form-factor Pluggable transceiver, generally called SFP+. Based on the Small Form-factor Pluggable (SFP) transceiver and developed by the ANSI T11 fibre channel group, it is smaller still and lower power than XFP. SFP+ has become the most popular socket on 10GE systems. SFP+ modules do only optical to electrical conversion, no clock and data recovery, putting a higher burden on the host's channel equalization. SFP+ modules share a common physical form factor with legacy SFP modules, allowing higher port density than XFP and the re-use of existing designs for 24 or 48 ports in a 19-inch rack width blade.

Optical modules are connected to a host by either a XAUI, XFI or SerDes Framer Interface (SFI) interface. XENPAK, X2, and XPAK modules use XAUI to connect to their hosts. XAUI (XGXS) uses a four-lane data channel and is specified in IEEE 802.3 Clause 47. XFP modules use a XFI interface and SFP+ modules use an SFI interface. XFI and SFI use a single lane data channel and the 64b/66b encoding specified in IEEE 802.3 Clause 49.

SFP+ modules can further be grouped into two types of host interfaces: linear or limiting. Limiting modules are preferred except when for long-reach applications using 10GBASE-LRM modules.

Optical fiber

There are two basic types of optical fiber used for 10 Gigabit Ethernet: single-mode (SMF) and multi-mode (MMF). In SMF light follows a single path through the fiber while in MMF it takes multiple paths resulting in differential mode delay (DMD). SMF is used for long-distance communication and MMF is used for distances of less than 300 m. SMF has a narrower core (8.3 μm) which requires a more precise termination and connection method. MMF has a wider core (50 or 62.5 μm). The advantage of MMF is that it can be driven by a low cost Vertical-cavity surface-emitting laser (VCSEL) for short distances, and multi-mode connectors are cheaper and easier to terminate reliably in the field. The advantage of SMF is that it can work over longer distances.

In the 802.3 standard, reference is made to FDDI-grade MMF fiber. This has a 62.5 μm core and a minimum modal bandwidth of 160 MHz·km at 850 nm. It was originally installed in the early 1990s for FDDI and 100BASE-FX networks. The 802.3 standard also references ISO/IEC 11801 which specifies optical MMF fiber types OM1, OM2, OM3 and OM4. OM1 has a 62.5 μm core while the others have a 50 μm core. At 850 nm the minimum modal bandwidth of OM1 is 200 MHz·km, of OM2 500 MHz·km, of OM3 2000 MHz·km and of OM4 4700 MHz·km. FDDI-grade cable is now obsolete and new structured cabling installations use either OM3 or OM4 cabling. OM3 cable can carry 10 Gigabit Ethernet 300 meters using low cost 10GBASE-SR optics. OM4 can manage 400 meters.

To distinguish SMF from MMF cables, SMF cables are usually yellow, while MMF cables are orange (OM1 & OM2) or aqua (OM3 & OM4). However, in fiber optics there is no uniform color for any specific optical speed or technology with the exception being the angled physical contact connector (APC), being an agreed color of green.

There are also active optical cables (AOC). These have the optical electronics already connected eliminating the connectors between the cable and the optical module. They plug into standard SFP+ sockets. They are lower cost than other optical solutions because the manufacturer can match the electronics to the required length and type of cable.

10GBASE-SR

10GBASE-SR ("short range") is a port type for multi-mode fiber and uses 850 nm lasers. Its Physical Coding Sublayer (PCS) is 64b/66b and is defined in IEEE 802.3 Clause 49 and its Physical Medium Dependent (PMD) sublayer in Clause 52. It delivers serialized data at a line rate of 10.3125 Gbd.

The range depends on the type of multi-mode fiber used.

MMF has the advantage over SMF of having lower-cost connectors; its wider core requires less mechanical precision.

The 10GBASE-SR transmitter is implemented with a VCSEL, which is low cost and low power. OM3 and OM4 optical cabling are sometimes described as laser optimized because they have been designed to work with VCSELs. 10GBASE-SR delivers the lowest cost, lowest power and smallest form factor optical modules.

There is a lower cost, lower power variant sometimes referred to as 10GBASE-SRL (10GBASE-SR lite). This is inter-operable with 10GBASE-SR but only has a reach of 100 meters.

10GBASE-LR

10GBASE-LR (long reach) is a port type for single-mode fiber and uses 1310 nm lasers. Its 64b/66b PCS is defined in IEEE 802.3 Clause 49 and its PMD sublayer in Clause 52. It delivers serialized data at a line rate of 10.3125 GBd.

The 10GBASE-LR transmitter is implemented with a Fabry–Pérot or distributed feedback laser (DFB). DFB lasers are more expensive than VCSELs but their high power and longer wavelength allow efficient coupling into the small core of single-mode fiber over greater distances.

10GBASE-LR maximum fiber length is 10 kilometers, although this will vary depending on the type of single-mode fiber used.

10GBASE-LRM

10GBASE-LRM, (long reach multi-mode) originally specified in IEEE 802.3aq is a port type for multi-mode fiber and uses 1310 nm lasers. Its 64b/66b PCS is defined in IEEE 802.3 Clause 49 and its PMD sublayer in Clause 68. It delivers serialized data at a line rate of 10.3125 GBd. 10GBASE-LRM uses electronic dispersion compensation (EDC) for receive equalization.

10GBASE-LRM allows distances up to 220 metres (720 ft) on FDDI-grade multi-mode fiber and the same 220m maximum reach on OM1, OM2 and OM3 fiber types. 10GBASE-LRM reach is not quite as far as the older 10GBASE-LX4 standard. Some 10GBASE-LRM transceivers also allow distances up to 300 metres (980 ft) on standard single-mode fiber (SMF, G.652), however this is not part of the IEEE or MSA specification. To ensure that specifications are met over FDDI-grade, OM1 and OM2 fibers, the transmitter should be coupled through a mode conditioning patch cord. No mode conditioning patch cord is required for applications over OM3 or OM4.

10GBASE-ER

10GBASE-ER (extended reach) is a port type for single-mode fiber and uses 1550 nm lasers. Its 64b/66b PCS is defined in IEEE 802.3 Clause 49 and its PMD sublayer in Clause 52. It delivers serialized data at a line rate of 10.3125 GBd.

The 10GBASE-ER transmitter is implemented with an externally modulated laser (EML).

10GBASE-ER has a reach of 40 kilometres (25 mi) over engineered links and 30 km over standard links.