Category 6 is generally good news for those seeking improved reliability. But the news isn’t all good. Now that the bar has been lifted on cabling performance, problems that before could be ignored have surfaced again, and end users may not be getting the improved reliability they were hoping for.

Short link problems are back with a vengeance! Some are caused by connectors that are simply not meeting the advertised claims while others are due to inadequately balanced connectors. If every short link had problems, detecting them would be easy. But the problems tend to only show up in certain configurations and frequency ranges. The ranges are furthermore sensitive to exact connector spacing, especially multiple closely spaced connectors. This makes channel compliance verification a challenge. A particular channel may pass with considerable margin with one cord length but fail with another length. Testing all foreseeable channel configurations in the lab has simply not been practical. Until now.

The Modal Decomposition Modeling Tool

After seven years of development, the Systimax R&D group at Avaya Labs has completed a fully functional testing system that accurately characterizes all 256 coupling parameters of 4-pair cabling and has used it to develop the Systimax GigaSPEEDâ XL Solution. The hardware shown in Figure 1 consists of a Hewlett Packard network analyzer and switch made to custom specifications as well as precision fixturing including semi-rigid coaxial cables and custom test heads.

Each component of a channel is measured separately. A database of channel component performance was created that includes connections (plug/jack combinations), standard cord lengths, and a wide range of cable lengths. Dozens of samples of connections and cables are stored to ensure the full manufacturing variance of each component is represented. These components were then cascaded together to accurately calculate channel performance. All the standard parameters defined in the cabling specifications were calculated as well as all parameters still under investigation, such as LCL, LCTL, cross-modal balance, etc.

Various sanity checks were performed to be sure the cascading approach yielded the same results as actually measuring the entire channel. Figure 2 shows the result of 6 components mathematically cascaded together relative to the results from directly measuring the entire 6-component channel. Excellent agreement is evident over the relevant frequency range even for high performance Category 6 cabling.

Accounting for the cross-modal coupling is critical to ensure accurate results. The example below demonstrates just how much performance can be robbed via unspecified secondary and tertiary paths. All 5 components in the channel were verified to meet the Category 5E NEXT requirement with ample margin. They were then cascaded together in a channel to calculate actual channel performance as shown in Figure 3. The actual channel failed Category 5E specifications by 1.1 dB. When the cross-modal coupling terms were mathematically zeroed out, the channel passed Category 5E specifications by 5.1 dB. Ignoring the cross-modal terms would thus have yielded inaccurate results with respect to the quality and reliability of this particular channel.

Thousands of channel configurations were simulated to identify the worst-case configurations for all the relevant parameters. Initial results on prototype connections quickly identified weak links requiring improvement or tuning for resonance minimization. User-friendly software routines not only qualified the weak links but also quantified the degree of weakness. Specifically, by mathematically scaling a particular component’s cross-modal coupling on the selected pair combination, the benefit in channel performance of a 50 per cent improvement in component performance is instantly known. Modal decomposition is thus a powerful tool in not only identifying the problem areas but also setting specific direction and objectives for component designers facilitating optimum tuning.

Perfection can never be reached. Some small secondary or tertiary coupling paths will always remain, but by utilizing a powerful tool such as Modal Decomposition Modeling, it is possible to get closer to perfection than ever before. The components that Avaya Labs has optimized with this tool are guaranteed to deliver performance that exceeds Category 6 channel NEXT by 6 dB in all certified 4-connector channel configurations. The connectors can be installed in any practical configuration, wherever the user wants them. No minimum cable lengths. No disallowed cord lengths. No restrictions, simply optimized performance and reliability. Channel architectures can even be extended to 6 connections with guaranteed 4 dB of NEXT margin for certified installations. Modal Decomposition Modeling facilitates the flexibility to do what you want to do, when you want to without restrictions and without surprises.

Conclusion

Reliability is what it is all about. It doesn’t happen by chance. It happens by attacking all sources of problems that reduce it. Cabling is one such source, attributing to 40 per cent of all networking problems.

Category 6 cabling will help. It isn’t just for the early adopters in the market anymore. It will soon be for the masses. Market analysts Gartner Group and BSRIA predict that 90 per cent of new installations will be based on Category 6 in 1 or 3 years (depending on the specific report).

But choosing Category 6 components mixed and matched together by a vendor can be a risky investment. 100-meter 4-connector channels may perform fine in the lab. But what about shorter channels where the same connectors are spaced closely together? Resonances can and do occur between certain closely spaced connectors under certain conditions. The electrical frequency of the resonance is design dependent and performance degradation is exacerbated with certain cable and cord lengths. The Modal Decomposition and Modal Cascade Simulation techniques mark the start of a new era for cabling designers and users. Until now, designers had to work with incomplete information on the factors determining the performance of their products. It was also impossible to test enough channel configurations to be totally certain that all of them would meet specifications. That has now changed and users can buy cabling solutions good enough to give their network infrastructure reliability that matches its enormous importance to their business. It’s time to take back control of your network. The technology is available today to help you build the reliability your users demand. Why wait any longer?

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