After months of trying to navigate the world of Category 8 cabling, IHS data centre and critical infrastructure research analyst Sarah McElroy debunks some of the biggest myths surrounding the new format.

In the few months that I have been researching the network cabling market, I have heard a wide variety of perspectives and opinions about the pending introduction of Category 8 copper cable, which will support 40Gbps Ethernet.

Never have I encountered a topic where I have heard such opposing viewpoints expressed. In the case of Cat 8, the ‘facts’ I hear from one supplier completely contradict the ‘facts’ I hear from another, especially when relating it to a comparable fibre offering. For this reason, I have set out to clear up some misperceptions associated with Cat 8 copper cable.

“Cat 8 is even larger in diameter than Cat 6a.”

TRUE.

While it is true that Cat 8 is slightly bigger than Cat 6a cables, the difference in size is far less than what is often claimed. A source close to the standard’s creation has stated that Cat 8 cables will only be a few hundredths of a millimetre larger in diameter. When looking at the two cables side by side, the naked eye would not recognise the difference in size.

Compared to fibre however, there is certainly no contest with regard to size. Fibre optic cables are often anywhere between one quarter to one half the size of a copper cable. One fibre is about the same size as a human hair, so these cables will inevitably be only a fraction of the size of copper cables, especially since they do not require shielding.

Size is a concern due to the limited space available in a patch panel or switch, especially as densities increase. For example there are now 48-port patch panels, and with the current size of copper cables and connectors, there is barely room to fit all those cables. There is really no room for cable or connector size to expand if high densities are to be achieved. Airflow is also a concern because it becomes increasingly difficult to get adequate airflow to switches with higher densities of cords attached to them.

“The increased weight of Cat 8 cable will cause problems for cable management and switches.”

FALSE.

Cat 8 cable will indeed be slightly heavier than Cat 6a cable. However, a source involved with the standard’s creation claims that the increased weight amounts only to a couple more pounds per reel of cable. This small amount of extra weight is not anticipated to cause problems for cable management or to create a dangerous amount of weight pulling on switches. Fibre optic cable by comparison is much lighter than copper cable and, additionally, will never suffer from the added weight of shielded layers.

“Cat 8 requires more power to run at 40Gbps speeds than fibre optic cable.”

TRUE.

It is true that it requires more power to run at high speeds over copper cable than fibre optic cable. The power required by a Cat 8 cable to run at 40Gbps can be depicted as a U-shaped graph with power on the vertical access and frequency on the horizontal access. Thus, there is a certain range of ideal frequencies (at the bottom of the ‘U’) at which the power needed is the lowest. While it is possible to optimise the power used by the Cat 8 cable, it will still always exceed that required by a fibre optic cable.

When thinking about power usage, heat becomes an additional consideration. Because Cat 8 cables (and copper cables in general) require more power, they also generate more heat than fibre optic cables and contribute to the need for increased data centre cooling efforts.

“Cat 8 cables will be standardised for a shorter length.”

TRUE.

The Telecommunications Industry Association (TIA) did a survey which showed that cable lengths of 50m or less will cover 90% of the cabling needs in a data centre. However, to make absolutely sure that they did not run into the same problems that prolonged the Cat 6a standards, the Institute of Electrical and Electronics Engineers (IEEE) decided that the standards be created for 30m. This may be completely adequate for some data centres; however, those needing cables longer than 30m will be limited by this and may find fibre optic cable to be the most viable option.

“Cat 8 does not have as much longevity as fibre optic cable.”

TRUE and FALSE.

It is true that fibre optic cable lasts for more than one cycle of install, and because of this, it usually lasts much longer than the typical copper instalment. Therefore, when looking purely at the length of time a deployment will last, fibre usually wins. However, Cat 8 copper (along with all other category cables) has another type of longevity in that it has the ability to auto-negotiate. Therefore, it has the ability to endure a multistage deployment. Because of the auto-negotiation capabilities, customers are able to upgrade electronics gradually instead of installing an entire new deployment all at once in order to implement a 40Gbps system.

“Copper is easier and better understood than fibre.”

…Let’s be honest, this is subjective.

People don’t like change and that is just a fact. It is frequently claimed that copper is easier to install and all installers can do it. You do not need any extra training or certifications to install or maintain a copper infrastructure. Proponents of Cat 8 will continue to site this as a compelling reason to stick with a copper infrastructure to satisfy 40Gbps needs as opposed to switching to fibre optics.

To be fair, there are many differences and terminating fibre cables is definitely a bit trickier. However, fibre has been around long enough by this point that there are many skilled installers, the fibre isn’t as fragile as it used to be and many of the concerns surrounding installation difficulties no longer apply.

While fibre continues to become more competitive, copper continues to strive to achieve the quality and speeds that fibre handily provides. Will contractors and customers stick with what they know or try something new? We will have to wait and see. Hopefully we won’t have to wait too long. The TIA will likely have standards completed by the end of 2015 while the IEEE standards are predicted to be completed shortly after, perhaps by the beginning of 2016.