Rosemary McGlashon, European technical manager, 3M explains that choosing the right (or wrong) cable will affect the data centre for years to come

While traditionally more expensive, fibre arguably has more benefits than copper cabling and in the long run, could prove the more economic option.  This is not to say that there is not a role for copper cabling - and indeed, for most to-the-desk installations today, it probably has the stronger business case - but as far as the data centre is concerned, fibre’s benefits are hard to ignore.
For instance, look at the lifetime cost of a structured cabling system.  True, in terms of the initial installation, copper will probably be more appealing to the finance director: the components are traditionally cheaper and involve less precision. However, this cost advantage is fast eroding, particularly since the price of raw copper continues to rise.   

Less power needed

Fibre also involves considerably less power consumption than copper:  estimates vary, but all are within the range of 10-15 watts per copper port, compared to just 1-5 watts per fibre port.  For data centres, this is a major issue.  A recent report carried out by industry analyst firm Quocirca found that almost half of data centres are aware that they are approaching power constraint, with 14% of data centres surveyed having already hit a power supply limit.  Over a quarter of companies have had a planning request for a data centre turned down due to lack of power.  

With copper cabling, the faster the data rate, the more power is required and this pushes up power consumption and costs.  In addition, the need to cool the system means that even when data is not being transmitted, power is being consumed.  It has been estimated that less than 10 per cent of power is used to transmit data.

In terms of production, fibre has less impact on the environment (as it does not need to be mined) and although it cannot be recycled like copper, it has a much longer lifespan, since today’s fibre cables are able to support increasing data speeds far into the future.  Copper’s capabilities are being pushed to the absolute limit: it is hard to argue its case much beyond 10Gbps.  Copper cables are bigger than fibre cables and require more plastic sheathing around the cable and, of course, plastic’s green credentials are another issue for debate.

Fibre cabling also takes up less space: typically, copper cable is estimated to be seven times heavier and needs five times more space.  This matters in space-constrained environments, including under-floor voids, where communications cables have to share space with other services, such as power and air-conditioning systems.  Also, fibre is higher density: it is possible to have more ports within a smaller space, since the patch-cords are considerably smaller and require less space for management.

Other benefits of fibre cabling include the fact that - unlike copper - it is resistant to electrical magnetic interference (EMI) and is also virtually impossible to ‘hack’.  Since it is a non-conductive material, fibre can also be used in environments where electrical isolation is needed, for instance, between buildings. Fibre also does not pose a threat in dangerous environments such as chemical plants where a spark could trigger an explosion.

Downsides

So does fibre have any limitations?  It is less simple to install, requiring greater skill than copper cabling, hence today there are fewer installation firms able to offer fibre installation, though this is changing.  There are an increasing number of cabling installers who are beginning to wake up to this market opportunity and new product developments are bringing fibre installation within the range of a greater number of companies: the introduction of No Polish Connectors (NPC) technology means that fibre ends do not need to be hand polished on site.  

This is a major issue: incorrect polishing of fibre ends can mean that a good contact is not established between the two cables, thus impairing performance.  Since the installer is handling a tiny surface area, the chances of getting the curvature of the polished surface wrong are high.  Other product innovations include fibre connectors that prevent the cables being connected incorrectly, and integral covers that ensure ambient particles – such as dust – do not get into the connection during installation.  

Of course, none of this obviates the need for experience and training, so it pays to do some research and choose an installer with a proven track record in fibre installation.  Over the years in which I have been involved in the cabling industry, I have seen entire cabling systems fail, even needing to be ripped out and replaced, due to installer error.

These mistakes are not just restricted to fibre cable installations.  Indeed, as structured cabling becomes more complex, due to the need to support growing high speed, getting the most out of copper requires more installation skill than ever before.  For instance, the latest standards in copper cabling (to support 10Gbit/s Ethernet) mean that installers need to be extremely careful about the accuracy of the terminations and cable bend radius.

Standards are changing

Industry standards also play an important role in ensuring good design and this is why a in 2007, the industry organisation that governs cabling standards in Europe – CENELEC – introduced an additional part to the updated standards specifically for data centres.  CENELEC EN 50173-5 is designed to address the specific topography of data centres, which have different requirements to typical desktop environments.  There are fewer internal connections between users or devices, but many more connections to external networks and, although data centre design is largely static, it is more ‘mission critical’ than many desktop applications, as well as handling vast amounts of data and requiring considerable resilience.  Cable management is important. For instance, cable runs should not exceed recommended distances and cables should be housed in such a way that there is no danger of crushing. Also, termination points should be accessible so that it is possible to carry out any changes in configuration that are required.

There are many other aspects of the standard, all of which are really only relevant for the installer to understand, but suffice to say it makes sense to choose an installer that is familiar with the intricacies of the data centre aspect of CENELEC EN 50173-1 and EN50173-5, which were finalised in the latter part of 2007.

Today’s cable system specifiers have a range of transport methods they can recommend to their data centre customers: 10Gb/s Ethernet copper,  10Gb/s Ethernet fibre and the existing Fibre Channel protocol, which can handle up to 8Gb/s, currently.  In addition, the creation of standards to support 40Gb/s and 100Gb/s Ethernet are now being worked on by the IEEE, with a nominal publishing date of 2010.  As data speeds increase, we are also likely to see more adoption of single mode fibre (SMF), which although more expensive than multimode fibre (MMF), will be able to handle the increased throughput far more efficiently.  Of course, there are alternative ways of achieving this, such as using line aggregation.  

We also expect to see an increase in the use of intelligent cabling. This involves an overlay of the system,  which monitors connectivity remotely and can be used to track moves and changes and unauthorised changes to the physical cabling. Intelligent cabling can also be integrated into active network supervisory programmes.

Clearly, there are many  issues for data centre managers to consider when investing in a cabling system.  This is why above all, it makes sense to work with third parties who have proven expertise, choose products that simplify installation and opt for fibre, which is able to meet the needs of the data centre both now and in years to come.