Considering interconnects

May 15, 2012 | Electrical & electronics

Many equipment manufacturers are facing a problem – the performance requirements for signal transfer are becoming ever more critical as data-rates continue to increase and the boundaries of physics lead to minimal headroom. This no longer permits the manufacturing variances that were acceptable in former times. Tom Aubin, CTO with integrated interconnect design and manufacturing company Volex, looks at the issues of high-speed data technology and the benefits provided by partnering with an interconnect provider

Once a simple commodity, interconnects now present a highly complex design and manufacturing task, and equipment manufacturers are finding they have neither sufficiently experienced design staff or in-house knowledge. Not only does this mean more design time is needed, but it frequently puts projects into serious delay – if, for example, an interconnect design fails and has to go through additional design iterations.

The internet has brought on this situation. The number of users worldwide has increased along with the bandwidth of the content – such as ever higher definition images and video – leaving systems needing to transport a huge amount of data traffic around.

Data centers, for example, are expanding in order to service their customers. However, the physical size of many cannot change and the cost of data centre real-estate moves rapidly upwards – so the equipment that goes into these needs to become more and more dense. As a result, data centre interconnects also have to become more and more dense, at the same time as moving data faster and faster.

Another example would be that of consumer electronics, such as the games consoles that will be coming out in the future. Here, the level of graphics that they’re going to deliver will be even higher resolution and include support for 3D displays. They will demand connectors and cables to link the console to the television that will have to provide 10 to 20 times the data rate of the current generation of games hardware. Soon, copper cables simply won’t be able to handle it.

The future development of the internet shouldn’t be underestimated in its influence. When I first had access to the internet, I was satisfied with the data rate I was getting over a modem connection – even though I’d have to wait for five minutes to download a document. Today that’s unacceptable, and people want instantaneous downloads.

The world of video transfer alone is driving significant changes in the interconnect world. Even corporate websites will become video rich over the next couple of years and it won’t be long before a high proportion of us have our TV delivered through the internet.

This will mean data centre, telecoms and IT devices will need to be able to pass much greater amounts of data almost instantaneously. But, the connectors that are doing that job today are not capable.

At the moment the interconnect world is still obeying Moore’s Law. The number of semiconductors per square inch is doubling every 18 months; and with that so are processing power, storage requirements and interconnect data rates. So where once a single channel SFP (small form-factor pluggable) connector was adequate, soon came the need for  SFP+ which had double the throughput, and then onto QSFP (quad SFP) a couple of years later using a connector only 50% larger than the original SFP. But at each speed increase, transmission limitations dictated shorter possible interconnect lengths.

There is a problem, however. Current predictions say the ability of data transfer is going to continue in a similar way for another five years or so before copper runs out of the ability to transfer these very rapid speeds without losses. We know, for example, that 40Gigabit/s over copper will be possible but only to around 7m.

The jury is out on 100Gigabit/s over copper and beyond. I’m not saying you can’t do it but to combat transmission losses, cables need to be wider and heavier; and sooner or later it won’t be practical in many applications to make copper cables any thicker. Furthermore, the achievable distances (sub 7m) will no longer be sufficient.

At Volex, we’re now seeing a lot of replacement of copper with optical solutions, and we forecast many more. As fibre optics is coming into its own, many manufacturers now face a move from copper to fibre, a technology they may have limited experience with.

Ask for help

Whether designing copper or fibre interconnects, the problem that electronic design engineers now face is that the signal loss budgets for the interconnects in their systems are becoming very small in order to obtain the bandwidth and data rates. So small, in fact, that many may not have the skills to translate those loss budgets into the connector, cable and termination selections required for the cable assemblies in order to guarantee dependable performance. If the wrong connector is then selected for the application, it won’t provide a reliable or workable interconnect solution for the project.

Other times the problem is that interconnects are low down the list of development priorities and can sometimes be seen as an afterthought. But, if you don’t design your interconnect until last and then have to change your initial design, you’re going backwards and having to do the project twice over.

Design teams who do not consider interconnects until the last minute are always in a redesign mode. They spend time solving problems that they should have addressed at the front end of the design effort, which can be costly both financially but also in terms of missed deadlines.

Asking for help from interconnect experts can offer many benefits. For example, in the aircraft industry people get bonus points for weight reduction. They want composite materials and anything that can do the job for the least possible weight because the compound effect of every gram reduced – over thousands of components – can make a significant difference to an airline’s fuel bills over the lifetime of each commercial or cargo plane. So shifting from copper to fibre not only gave them higher data rate connectivity, it gave them additional advantages of weight reduction and EMC (electromagnetic compatibility).

To be competitive, many companies have taken advantage of horizontal integration. Sub-contracting means they can focus on their core competencies.

Interconnect partners

When you’re looking for an interconnect provider you need one that will significantly contribute to the design process, one that will look at your equipment design (preferably as early as the block diagram stage) and ask the right questions. So that, at the end of the main design process, all of the interconnects are already designed, tested and accomplished and there’s no trial and error.

For example, we’ve worked with a firm that manufactures medical imaging equipment – it wanted to sharpen up the image produced by one of its scanning devices, while at the same time reducing the number of cable assemblies. As a solution, we created a hybrid product where we eliminated a lot of radio frequency lines, replacing them with optical lines.

We also combined everything into a single customised multi-function connector which included the power, the input signal from the scanner, and the optical signal which feeds the display.

On top of this we also had to consider all of the environmental and safety issues, such as flammability, patient contact and the necessity of avoiding magnetic materials, to take into account differing requirements in the different countries and regulatory regimes that the equipment would be operated in. There are a mass of issues that go into the requirements for a cable assembly.

Over the years, we’ve found that the best way to mitigate the potential risks when leading edge equipment designs demand leading edge interconnect designs is to undertake non-disclosure agreement (NDA) based technology roadmap sharing, where we offer our partner customers our full expertise in how we see the market and technology evolving and what we’re doing to address it in terms of our competencies, capabilities and design projects internally. And our partner gives us an equally frank vision of where they see their own technology roadmap going and what this is going to mean in terms of interconnect capability requirements. The result is that both companies are much better prepared for the future, and can amend their plans based on knowledge shared, meaning that firms which work with us in this way can design products with the certainty that the necessary interconnect technology is being developed in parallel and will be supported through future versions.

The science of interconnects

Keeping up with all the latest advances in high-speed data connectivity is a very time consuming job. As an integrated interconnect design and manufacturing company we sit on many of the international standards committees – such as IEEE and VESA – and help to influence the decisions they make. As a result we are aware of up-coming connectors and technical performance requirements of the transmission channel often two or three years before the design engineers at our customers.

Having an integrated design and manufacture interconnect house as a strategic partner can save significant money, reduce time to market, help plan and design for the future, whilst complying and benefiting from early understanding of upcoming and complex existing global standards.



Social Icons

Button Ads