Impulse noise introduced when some installed cables are moved or flexed (i.e. “mechanically generated”) may induce transmission errors to the signals carried over some balanced twisted-pair cabling systems.  This mechanically-generated noise has neither been demonstrated to be catastrophic nor even service affecting, but may be noticeable when testing sensitive systems for extremely low bit error ratio performance.  This impulse noise is not observed on all copper cables and has not been observed or expected to impact either cabling or equipment in other ways due to the low energy in the impulses themselves.

TSB-5008 “Mechanically-Generated Cable Impulse Noise Detection and Characterization” was developed by the TIA TR-42.7 Copper Cabling Subcommittee and published in December, 2014.  TSB-5008 describes the impulse noise that can result when flexing some cables, provides example test results showing the pulse amplitude, bandwidth, variability, and time decay of an impulse event, and outlines testing methodologies to characterize the induced impulse noise in a cabling system.  TSB-5008 explicitly states that mechanically-generated impulse events are uncommon and should not be a cause for concern.  TSB-5008 contains the following additional explanatory information:

  • Mechanically-generated impulse noise is attributed to the electrostatic charge that accumulates when different dielectric materials come into contact with each other and then separate; either by rubbing or friction.
  • This phenomenon is called the “triboelectric effect” or  “triboelectric charging”.
  • Different cable types and designs exhibit varying levels of cable impulse noise when tested under the same conditions.
  • Mechanically-generated impulse noise is not observed on all cables.
  • Vibration does not cause impulse noise effects.
  • The duration of a mechanically-generated impulse noise event is typically less than 10 nanoseconds.
  • While there may be a temporary drop in bit error performance during an impulse noise event, there is no long term impact on the performance of Ethernet and other standardized communications applications.

TSB-5008 Content

  • Mechanically-Generated Cable Impulse Noise
  • Cable Impulse Noise Measurement Procedure
  • Cables Impulse Noise Characterization
  • Guidelines for Optimizing Channel Performance with Regard to Mechanically-Generated Cable Impulse Noise

 

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