After debating the issue for three meetings cycles, the TIA TR-42.7 Copper Cabling Subcommittee adopted “category 8” as the name of their next generation balanced twisted-pair cabling system that is currently under development to support 40Gb/s transmission in a 2-connector channel over some distance up to at least 30 meters.  The issue of what to call this new system was a subject close to the hearts of many subcommittee members and both proponents and opponents of the new name argued tenaciously for their positions. However, the real question is just how much confusion the name category 8 is going to cause for the industry.

Traditionally, cabling categories are supersets of each other – meaning that a higher category of cabling meets or exceeds all of the electrical and mechanical requirements of a lower category of cabling and is also backwards compatible with the lower performing category.  While TIA specifies cabling systems up to category 6A performance, TIA chose not to adopt category 7 or 7_A as published by ISO/IEC.  TIA has now decided to call their next generation cabling system “category 8” to avoid confusion with published ISO/IEC category 7 and category 7_A standards, which are indeed supersets of each other and of category 6A.  While it’s true that the currently proposed category 8 specifications tentatively describe transmission performance up to 2 GHz whereas ISO/IEC specifies category 7_A requirements up to 1 GHz, the performance limits proposed for category 8 today do not meet or exceed category 7_A requirements up to 1 GHz.

So, herein lays the conundrum: category 8 is expected to have a different deployed channel topology and will not be a performance superset of category 7_A.  In fact, for every transmission parameter except return loss, ISO/IEC category 7_A channel and permanent link limits are more severe than those proposed by TR-42.7 for category 8 up to 1 GHz.  In the case of internal crosstalk parameters, the differences are significant: with category 7_A beating out category 8 performance by more than 20 dB!

So what about bandwidth of specification?  While category 7_A is currently specified to 1 GHz, new work items, such as the nearly finalized IEC 61076-3-104, 3rd edition standard for category 7_A connectors, are extending category 7_A performance characterization out to 2 GHz.  The situation of having two cabling specifications specified to 2GHz, with category 8 having much lower performance than category 7_A, is really going to create confusion.

What to name next generation cabling systems is not just a TIA issue; ISO/IEC also faced the same challenge with their new project to define two new grades of cabling (shielded and fully-shielded) to support 40 Gbit/s data transmission.  ISO/IEC recently adopted class I to describe cabling constructed from shielded modular RJ-45 style category 8.1 components and class II to describe cabling constructed from fully-shielded category 8.2 components.

Until the processing capabilities of a 40 Gb/s Ethernet (40GBASE-T) application are finalized, it’s too early to guarantee 40GBASE-T application support distance for any media. However, fully-shielded category 7_A solutions, such as Siemon’s TERA™, remain the highest performing twisted-pair cabling system commercially available today.  Not only do these solutions provide higher EMI/RFI immunity and more flexible cable sharing capabilities than RJ-45 style solutions, but ISO/IEC is actively working on a project to characterize the capability of existing category 7_A cabling to support 40 Gbit/s data transmission.