25GBASE

25GBASE refers to a family of Ethernet physical-layer standards that support 25 gigabits per second on a single lane. Defined by IEEE 802.3 in 2016 as part of the 25 Gigabit Ethernet family (802.3by), 25GBASE was designed to provide higher bandwidth and better efficiency for data centers, offering a practical step between 10G and higher-speed Ethernet. The standards describe multiple media options and corresponding optical or copper interfaces, enabling flexible deployment across short and long reaches.

Common variants within the 25GBASE family include 25GBASE-SR, 25GBASE-LR, and 25GBASE-LRM. 25GBASE-SR is used over multimode fiber with 850 nm signaling and is intended for short-reach connections, typically up to about 100 meters on common multimode fibers. 25GBASE-LR uses single-mode fiber with 1310 nm signaling for longer links, often up to 10 kilometers. 25GBASE-LRM targets longer-reach connections over multimode fiber, using 1310 nm signaling to bridge intermediate distances. In addition to these fiber options, 25GBASE-CR defines direct-attach copper cables (DAC) with SFP28 connectors for short, cost-effective links, commonly used for server-to-switch or inter-rack connections, with practical lengths up to several meters depending on cable design.

Form-factor and hardware support are central to 25GBASE adoption. Transceivers commonly use SFP28 for single-lane 25 Gbps links, while higher-density deployments may employ QSFP28 modules. The standard is widely used in data centers to enable higher uplink bandwidth with lower power and footprint per bit compared with earlier generations, and it complements other Ethernet speeds within the evolving 25/40/100 Gbps ecosystem.