Smart Building

Why You Need Cable Insertion Loss Margin

Ron Tellas

In most cases, when it comes to cabling and connectivity, it’s better to play it safe instead of cutting it close. For example: You don’t want a cabling system that can barely support your current application requirements. A system that is fully capable of handling current application bandwidth needs, as well as future needs, offers more peace of mind, ensures continued productivity and reduces the need for costly upgrades later.

The same holds true when talking about cable insertion loss margin. Insertion loss is the ratio of received to inserted signal power at the end of a cable and is dominated by the cable attenuation. Expressed in decibels (dB), insertion loss levels increase as cable temperature rises.


Cable insertion loss margin represents the difference between the cable’s measured insertion loss and the maximum insertion loss level allowed per standards; the higher the margin, the better the cable performance. Cutting it close when it comes to cable insertion loss margin doesn’t leave much wiggle room for cable temperature levels to rise without experiencing negative impacts.


What the Requirements Say

The insertion loss requirement given in the standards is at 20 degrees C. If cable temperatures exceed that level, which reduces insertion loss margin, performance requirements must change to accommodate the higher temperatures – otherwise, you’re not taking full advantage of what your cabling system has to offer.


If controlling the temperature of the environment is not an option, channel lengths must be shortened to continue to move data along the cable; otherwise, data transmission will suffer (there will be too much cable loss for successful transmission). How much the channel needs to be shortened depends on the construction and type of category cable being used: Category 5e, 6 or 6A. Reduced cable insertion loss margin will also reduce information capacity, lowering signal-to-noise ratios (which indicate the relationship between desired signals and background noise levels).


Sufficient Insertion Loss Margin

Sufficient cable insertion loss margin is especially crucial in Power over Ethernet (PoE) applications, as well as in digital buildings and IoT environments, where DC current is running through cable bundles along with the data, causing heat build-up if it  doesn’t have a chance to dissipate into the environment.


Lower-tier manufacturers cut it close when it comes to designing cable to pass cable insertion loss requirements. Instead of offering ample insertion loss margin, they run as close to the edge as possible, with little or no margin to spare.

Minimally compliant cables may pass the 20 degrees C performance requirement, but problems will occur as soon as the cable gets warmer due to increased ambient temperature or the addition of PoE loads.


Belden manufacturers its cables with sufficient cable insertion loss requirements to make sure network performance doesn’t suffer due to cable temperatures. Designed to transmit data up to 100 m, our Category 6A cabling features enough insertion loss margin to handle the extra heat generated from bundled cables while still maintaining full channel lengths.