Twisted-Pair BASE-T Connectivity

Since the ratification of the Ethernet standard, the most common type of connectivity has been based on copper wires and related connectors. New IEEE and consortium standards are focused on the growing need to support higher bandwidth, but copper connectivity still brings unique value, even when compared to newer technologies.

The RJ45 connection was originally developed for the telephone industry as a less-expensive connection method compared to hardwiring. A modular connection was developed to connect computer networks for similar reasons. The 8P8C (eight-pin, eightcontact) connector is an Ethernetspecific network connection. This connector is very similar to the original RJ45 and over time became commonly referred to by the industry as RJ45. The RJ45 supports a wide range of speeds, depending on the category of the cable and connected network adapters. 

While the RJ45 form factor has not changed, new categories of twisted-pair cables have emerged to support higher bandwidth connections. Keeping the RJ45 connector constant allows for easier infrastructure upgrades to higher speeds.

Twisted-pair copper cable is a type of cabling where internal pairs of wires are twisted together to provide protection against crosstalk, the electromagnetic noise generated by adjacent pairs. Compared to a single conductor or an untwisted balanced pair, a twisted pair guarantees better resiliency of transmitted signals on external disturbance. 

There are several forms of the twistedpair cable, each of which comes with different levels of electromagnetic protections: unshielded, or twistedpair, and shielded). Shielded-pair wires are covered with foil or braided screen to provide added protection against alien crosstalk, but can also increase cable diameter, depending on the manufacturer.

Requirements for bandwidth are constantly increasing. New categories of cables are developed to support the higher frequencies required and to protect signals from electromagnetic interference.

One of the main benefits of twistedpair copper cables is that newer categories are backward compatible, providing better total cost of ownership and easy upgrades. Newer categories of twisted-pair cables can support highbandwidth standards. However, these kinds of cables are more costly and less flexible, potentially impacting their use throughout a network.

Today there are two main standards that stipulate the division of twistedpair categories and classes: the International ISO/IEC 11801 Standard1and American TIA/EIA-568B Standard.

The shielding types have clearly defined markings that are recognized by international TIA/EIA-568B Standard. 

A special code designates the type of cable (figure 4).

Category 5e (CAT5e) standard cables are defined in TIA/EIA-586 and are available in three types. Each cable type uses 1.5—two twists of pairs per centimeter of cable:

The Category 6 (CAT6) standard provides the same levels of additional shielding as CAT5e with the main difference being the number of twists per centimeter in the conductor 

pairs. According to the TIA/EIA-568B standard, CAT6 cables must have two or more twists for each centimeter and may additionally include a nylon spline to reduce crosstalk between pairs. This type of cable can provide 10GBASE-T connectivity but is limited to 55 meters. 

Category 6A (CAT6A) provides the same shielding configurations as the previous categories and includes S/FTP, a braided shielding outer layer, and foil shielding for each twisted pair of conductors. This type of protection allows 10GBASE-T connectivity over a full 100 meters.

Table 1 shows the types of BASE-T cables and maximum distances for each.