Here's a couple of questions I received regarding the aesthetics of an installation,
and crosstalk.
Question 1
I have a question regarding crosstalk between data cables in a bundle. It is my
understanding that cable cross-talk is potentially greater when cables in a bundle
lie parallel to each other, and lie in the closest possible bundle configuration.
However, data center installers like to install the cable in this very 'neat'
configuration for aesthetics and space savings.
Is there any way to reduce this crosstak (besides using a better cable). For
example, I noticed that the four twisted pairs in data cable are also twisted around
each other. Could the entire bundle of data cable be twisted to improve cross-talk
performance?
Question 2
I am a certified cabling designer and Installer. I have a question. I tried but failed to find a good answer.
Can you help me.
I was discussing with a friend of mine who is in the same field as me. The horizontal cables when
entering in the MDF/IDF room, should they be combed parallel to each other or not or should they be
left mingled and sorted when they are near the patch panel? Should it be combed and all the cables
from false ceiling to the entering the cabinet be combed for aesthetic reason. Or it should remain
mingled as the UTP cables are twisted inside their jackets.
I believe combing the UTP cables and make them run in parallel to each other may produce noise or
some other distortion in the transmit or receive of signals.
Answer
This is a question I asked a few years ago. I have worked for a lot of companies who all insisted on
making the cabling looms look aesthetically pleasing and the only reason for doing this is to make the
installation look more professional.
I spent quite a lot of time many years ago working as a prototype wireman for a company who
produced control systems for submarines. On my first attempt at wiring a circuit board, I made it look
very "professional" all the wires were parallel and neat. Very pleased with myself for making such a
good job I showed the boss, he told me to cut all the wires off and start again! He explained that the
circuit board was for a high frequency telecommunications system and that it simply wouldn't work
because the parallel cables would cause too much crosstalk, "just wire it point to point, don't worry
about what it looks like" he said.
The fact is, that although comms cabling looks better
if all the cables are combed and loomed in parallel, it
serves no purpose other than making the installation
look tidy.
The term for noise between adjacent cables is called
"alien crosstalk" but there is very little written about it
and not a great deal of proof that it actually effects
the signals.
Theoretically, in high speed communications cabling,
the messier the installation is, the better it will work.
Hope this answers your question!
Alien Crosstalk! - How neat should an installation be?