2018年4月8日星期日

Cut Off Cables: To splice or not to splice?

by Fiber-MART.COM
I have been in the business of installing voice, data and fiber optic cabling for about 30 years and I have been asked this question many times. Most situations usually happen if you are looking at moving your company into an existing building that has some cut cables. So let’s use that scenario.
 
Cut cables in an office environment
You are moving into an existing facility and there is an open area where cubicles used to be. Whoever removed the cubicles just cut off the cables. And let’s say the rack and patch panels are still present in the main distribution frame (MDF), also known as the server room, computer room or data room etc., and all the cables are still terminated on the patch panels.
 
Now if these cables are old category 3 or category 5 cables, they are not worth keeping due to newer faster switches and VoIP phone systems. However, if they are category 5e cables or above there are some choices to be made other than pulling all new cables.
 
If you planned to put modular furniture back in the open space, there is a great solution called a Zone Cabling Box (ZCB). These boxes mount in the 2×2 or 2×4 ceiling grid and can be installed in the area above where the cut cables are to short to reach the modular furniture. They blend in with the ceiling tiles and open down for easy access. You can even get these with power if you want to mount a switch here as well.
 
So inside the box, you can mount the category rated 110 blocks to match the existing cables and terminate them to one side of the block. Now you run new cables from here to the voice / data outlets in the modular furniture. Terminate the cables to the opposite side of the block and there you have a proper splice point or also called a consolidation point.
 
Another alternative solution would be to use one cable from the Server Room to connect to a new switch installed in the ZCB. Then run new cables to the modular furniture and terminate those cables onto a patch panel also in the ZCB. You can then patch into the switch which now becomes an intermediate distribution frame (IDF).
 
Cut off cables at a wall outlet should be replaced with a new cable or pulled up the wall and moved to another outlet location it will reach.
 
Cut or Short Fiber Optic Cables
I only recommend two types of fiber splicing or extending a fiber cable.
 
The first and best way is to fusion splice the fiber strands to another fiber cable of the same gender. For example, you would fusion splice a multi-mode 50um to a matching 50um fiber cable or a single mode to a single mode fiber optic cable.
 
The second way is to terminate the fiber into a patch panel and then using patch cords, patch the fiber strands together.
 
The third way is called a mechanical splice. This is older technology replaced by much better fusion splicing.
 
To put this in perspective, it will always be better to have a cable that is intact from end to end. This ensures proper transmission speeds needed for your network. So when in doubt always replace a cut network cable. Or, contact a highly trained certified low voltage contractor, especially one who has a Registered Communications Distribution Designer (RCDD) on staff. A specialist can help recommend the best solution for all your cabling needs.
 
How to Fix a Cut Cable In a Home Environment
As we discussed above, it is always better to have a cable that has never been cut or damaged. If you do need to splice a cable in your home, it should only be temporary. A spliced cable will probably fail at some time, or at a minimum lessen the signal to your device. So let’s talk about twisted pair cable first.
 
Your phone line is usually brought into your home via a category 3 or less copper cable. The phone company splices this cable together in several places along the way to feed everywhere they need to get to. This is a very low-end cable with slightly twisted pairs inside the sheath. It usually comes into your home from a telephone pole aerial or buried underground. If you cut this cable accidently, for example while landscaping, you should call your local phone carrier. They will be able to professionally splice the cable using a weatherproof splice kit or they will run a new cable.
 
If you cut any twisted pair cable on the inside of your home, simply twisting the ends together is not a good solution and not recommended. Your two best options are as follows, and you may need to hire the services of someone who knows how to do this and has the proper termination tools.
 
The first way is to re-terminate the cut ends onto a small termination block. This block allows the signal to transfer from on side of the block to the other and gives a good connection that, if done correctly will work well. This is also similar to the way I explained how a cut cable can be re-used in a zone cabling box described above.
 
The second way is to terminate each cut end to an RJ-45 plug. This is the type plug you see on each end of the patch cord at your office desk or coming off your router at home. You then connect each end into an RJ-45 to RJ-45 pass thru block. This is no different from using the block scenario mentioned above. Both simply pass the signal from one side to the next in a proper manner. Both of these options can also be used to extend a cable that needs to reach a further end point.
 
Cut COAX Cables in a Home
This is similar to twisted cables as you simply re-terminate the cut ends of the cable with new COAX RG type connectors and then screw each end into a COAX barrel connector. This will also lessen the signal strength to your TV.
 
Keep in mind that either COAX or twisted pair cables might be too short or damaged in several places and several inches or feet from the actual cut. In this case, they may just need to be replaced.

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