More than century after eight-year old Virginia learned from the editor of the New York Sun that there was indeed a Santa Clause, IT managers and end users who recently learned about TIA’s latest “category 8” can rest assured that there is indeed an existing standards-based category 7_A.

Yes, that’s right. After much debate, the Telecommunications Industry Association (TIA) TR-42.7 Copper Cabling Subcommittee recently adopted “category 8” as the nomenclature of their next generation balanced twisted-pair cabling system to eventually support 40 gigabits per second (Gb/s) in a two-connector model at some distance shorter than 100 meters (m). TIA moving consecutively from category 6A to category 8 has caused some confusion in the industry, and some are asking, “Is there a category 7?”

As was so eloquently put to little Virginia regarding the existence of Santa Clause when the editor responded, “Your little friends are wrong. They have been affected by the skepticism of a skeptical age,” the same holds true for category 7_A. Despite what the skeptics say, this standards-based cabling system is here now and here to stay. Furthermore, it offers the benefit of interference-free cable sharing.

A Standards-Based Existence

Ratified in 2002 by the International Organization for Standardization (ISO) under ISO/IEC, 11801, 2nd edition, category 7 (class F) cabling, is a fully-shielded cable characterized up to a bandwidth of 600 megahertz (MHz). In 2010, Amendment 2 of ISO 11801 specified performance for category 7_A (class F_A) cabling. Also a fully-shielded S/FTP cable, category 7_A offers an extended frequency bandwidth of up to 1000 MHz. Siemon’s TERA 1000 MHz cabling exceeds all ISO/IEC requirements for category 7_A/class F_A transmission performance.

Due to its fully shielded design, TERA 1000 MHz category 7_A cable provides higher performance than unshielded twisted-pair (UTP) cabling. At higher frequencies, the use of individually shielded pairs virtually eliminates internal crosstalk between pairs and external cable-to-cable alien crosstalk, both along the cable run and at the connector. In fact, at 1000 MHz, TIA’s proposed performance limits for category 8 do not currently meet those specified for Siemon’s TERA category 7_A cabling. Furthermore, the cable’s outer overall braid shield provides additional strength and a low impedance path to ground that provides superior resistance to electromagnetic interference and radio frequency interference (EMI/RFI).

ISO/IEC specifies two connector options for category 7 and 7_A—an RJ-style connector as defined by IEC 60603-7-7 and a non RJ-style connector as defined by IEC 61073-3-104. The non RJ-style connector is based on Siemon’s TERA connector, which when installed as part of a complete TERA solution, delivers up to 1.2 GHz of bandwidth to exceed the bandwidth of category 7A/class FA specifications.

Unlike the RJ-style interface, the TERA connector offers a unique isolated quadrant design interface that that allows easy access to one or two pairs of a channel to better accommodate cable sharing—the practice of running more than one application over different pairs of a twisted-pair copper cable. Some skeptical designers and consultants are still concerned about specifying cable sharing because they are unsure of the Standards’ acceptance of the practice. The good news is that both TIA and ISO recognize and provide guidance on cable sharing implementation. In fact, ISO/IEC 15018 specifically recommends that cable sharing be considered when pathway space is limited and identifies the IEC 61073-3-104 TERA connector as the preferred interface for this application_.

Doing Its Fair Share

Fully-shielded cabling systems like Siemon’s TERA category 7_A system are much better at cable sharing than unshielded twisted-pair (UTP) cabling. That’s because the internal crosstalk coupling (both near-end and far-end) in UTP cabling systems makes it difficult for users to predict whether multiple applications can coexist in one cable. In fact, standards caution that when deciding which applications can share a UTP cable, users should be aware that crosstalk from applications operating in similar frequency bands can potentially interfere with one another. On the other hand, a TERA system guarantees that there is sufficient noise isolation between pairs to support multiple applications, or the multiple appearance of any one application, over a four-pair channel.

How specifically does cable sharing work? As with any category 7_A cabling channel, all four shielded pairs are terminated to a single TERA outlet. However, in addition to accepting a 4-pair cord, the TERA connector can also support four 1-pair cords, two 2-pair cords, or a combination of the two—without the need for splitters or adapters. A single TERA outlet can therefore support multiple 1- and 2-pair low-speed applications or one 4-pair high-speed data application like 1000 Mb/s (1000BASE-T) or 10 Gb/s Ethernet (10GBASE-T). Cable sharing implementation practices are extremely flexible and support a wide range of configurations. The table below shows some typical 1- and 2-pair applications that can easily be supported with this cable sharing method.

By allowing various applications to be converged onto a single cable, the unused pairs that would be present if a 4-pair channel was dedicated to an application transmitting over just one, two, or three pairs are eliminated. TERA’s cable sharing capabilities therefore significantly reduces the number of cables required, subsequently reducing pathway costs and cable management complexity. For example, in a call center a single TERA connector can support four 1-pair analog phones for a cost savings in excess of 10 percent for materials and a 39 percent reduction in the total number of outlets.

Here Now and Here to Stay

While category 8 may now be on the TIA table, Siemon’s TERA category 7_A is an existing standards-based system that provides the benefits of cable sharing, higher bandwidth capacity and EMI/RFI immunity. And ISO/IEC is already looking toward the future with this technology. The nearly finalized IEC 61076-3-104, 3rd edition, will extend the performance of the IEC 61073-3-104 Siemon TERA category 7_A connector out to 2 GHz—the same frequency tentatively proposed for category 8.

Until the processing capabilities of a 40 Gb/s Ethernet application are finalized and more advanced and representative real-life analysis can be conducted, it is too early to guarantee 40 Gb/s support for any copper media. However, it does look as if Siemon’s fully-shielded category 7_A TERA system with its unique connector design will ultimately provide some support for next generation speeds of 40 Gb/s while offering the innovative capability of cable sharing.

So yes, IT manager, there is a Category 7_A.