40G Ethernet and Cat 8 Cabling

The IEEE states that we should “Expect 2020 data speed to be 100 times what they were in 2010”, i.e. we will be looking at Terabit Ethernet (1000Gb/s). These types of data rates are already in use in the telecommunications sector but only on singlemode fibre. The ever increasing demand for data of all sorts and the need to access and store that data means that data centres require cabling solutions that enable switches and servers to communicate at very high speeds.

In the past there has been a 10 fold increase in data transmission rates between consecutive generations of Ethernet but that trend is likely to be broken. Various bodies and active equipment manufacturers have proposed different potential data transmission rates, including 25Gb/s and 50Gb/s but the IEEE have already started working on 40G Ethernet over shielded twisted pair copper cabling. 40Gb/s solutions are already available over fibre and Twinax but these are either costly, in the case of fibre, or limited to very short distances (7 metres) on Twinax.

Twisted copper pairs are the most popular transmission medium used in local area networks (LANs) so this is the medium that the IEEE are working to support through 40GBASE-T (802.3bq). There is a desire that 40GBASE-T can be supported on current cabling infrastructures but cable length will be limited to 10-15m on Class EA (Cat 6A). It will only be supported on a 2 connector channel, i.e. panel to panel or panel to outlet, and will, therefore, be limited to data centre applications and is not being developed for general commercial installations.

The TIA has started work on Category 8 components, permanent link and channel specifications. Category 8 is intended to be backwards compatible to Cat 6A, Cat 6 and Cat 5e. It will use twisted pair cabling to support 40Gb Ethernet.

ISO/IEC is working on new Classes of cabling. Class I will use Cat 8.1 components and will be specified for frequencies up to 1.6GHz. Class II cabling will use Cat 8.2 components and will be specified for frequencies of up to 2GHz.

Both standards bodies are using the same assumptions, the use of 4-pair, balanced twisted pair copper cabling in a Channel using 2 connectors with a maximum cable run length of at least 30m. The connector type has yet to be determined, although the ARJ45 connector appears to be the preferred option. This connector has an RJ45 footprint but the four pairs of contacts are positioned in the four corners of the aperture, rather than in a row across the top of the plug/socket.

RJ45 Socket Image                    ARJ45 Socket Image

The RJ45 and ARJ45 plugs are not interoperable so adaptor cables will be required to connect cabling systems with ARJ45 connectivity to legacy equipment.

The IEEE 40GBASE-T specification is expected to be ratified in 2016 and cabling specifications from ISO/IEC, TIA and CENELEC are likely to follow in 2017. It is certain that any cabling specification will, for the first time, only include shielded cabling.