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Fiber installs?

N

netsysadmin

Senior member
I see them installing the blue and orange piping next to the road all the time. How does that install work? Is that tubing that they connect together and then install the actual fiber later or is the fiber already in there? I know there are some guys here on the board that know the process, how does it work?

Thanks,

John
 
Sometimes they use direct burial, and sometimes they use conduit, depends on the application and installer.

Direct burial is armored well and doesnt need a conduit to be buried in.
 
Most places install ducting first, and then thread the fiber through it. Generally, this is preferred as ducts are much easier to spot, if the same area needs to be dug up for further utility work. Ducts also provide additional protection for the cable. There is also the issue of upgrade - if you've got ducts, its pretty straightforward to add another cable at another date - or replace a segment of damaged cable (a major problem with important fiber runs, as repairs to a fiber cable are fiendishly expensive - it may be cheaper to replace a run).

There are a number of ways of getting cables into ducts. Often a rope will be pre-threaded into the ducting. You simply tie the rope to your cable and pull it through. If you don't have a pre-installed rope, you can use a 'fish-tape' which is a flexible rod with a flexible, spring metal tip. You push the rod into the duct - the flexible 'fish-tape' end will tend to find its way around corners, and you keep pushing (and attaching additional lengths of push-rod), until the fish-tape emerges out of the other end of the duct. At which point you tie a rope on, and pull it through.

The total length of ducting that you can pull through depends on the weight of cable, length of duct, number/tighness of any bends and strength of cable (if you try to pull too far, the pulling force through friction may be sufficient to snap the cable). Typically for fiber, the maximum 'pull' length is about 1000 meters.

Fiber is sufficiently light that it is possible to use a clever technique to install it into underground ducts. This is called 'blowing'. You connect an air compressor to the duct, with a special nozzle that has a hole for the cable. The cable then gets carried through the duct by the flowing air. To avoid stressing the cable, you can attach little parachutes every few hundred yards, so that the cable gets pulled evenly along its length, instead of just from the end. It's possible to blow up to 5,000 meters in one go - although up to 12,000 meters have been achieved in special circumstances.
 
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That vacuum they use to suck/blow installs is frickin cool. Damn thing is pulled around on a trailer, it aint no Kirby thats for sure! (Although a Shop Vac can be used in some limited circumstances)
 
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