33

I'm starting on a project that will involve digging a long (roughly 150-200 meter) trench from my house down to the road. The trench itself will be a considerable expense and so while the ground is open, I plan on laying additional conduit(s) containing any telecom links we may ever want, both for connecting to services currently available and ensuring we can use any services that might become available later. Currently only phone and cable are available at the road, but fiber-to-the-home has become available in other areas around us recently and I would hate to lose out by not being ready for it should it become available here.

Based on the distance, multimode fiber seems the best general option (vs CAT5/6 or singlemode fiber). POTS/DSL and cable are also available at the road currently.

To the specific questions:

  • Is MMF really the correct choice, vs SM fiber or CAT6? Should I run both MM and SM?
  • How many fiber lines is it reasonable to run for redundancy/backup? Should I include 2 or 3 lines from the outset?
  • Is it safe/reasonable to run fiber, coaxial cable and POTS all in the same conduit over this distance?
  • In principle, laying a second, empty, conduit with a strong comealong wire seems reasonable, but actually using it would certainly require a winch of some kind to pull it through over this distance, and I don't know if it is even practical. Any thoughts on this welcome.
  • What additional cabling besides fiber, POTS and coax should I consider for future proofing this run?

I've done in-premises CAT5 installs before and played with fiber a bit at work but am not a network engineer so I suspect there are some unknown unknowns and would appreciate any comments or insight you may have. Thanks.

Improve this question
6
  • 2
    Have you asked the nearest fiber-to-the-home provider what they put in the ground? And if you are able to pull cable once through your conduit, you should be able to do it again in the future. (Just avoid sharp angles.)
    – Aloysius Defenestrate
    Commented May 15, 2015 at 14:16
  • Note that 200 meters is way beyond the length limit for ethernet over CAT5e or CAT6. (Although it doesn't sound like that was necessarily part of your plan.)
    – Hank
    Commented May 15, 2015 at 15:05
  • 1
    I've hand-pulled thick cable/fibre bundles through thin conduits up to 100m using paracord (the good stuff, which is all you can get in such long pieces, not the stuff they sell in camping shops). I didn't even have to pull hard. I pulled that into place with some thin wire drawn by a domestic vacuum cleaner duct-taped on. Don't worry about breaking strain or pulling capacity so long as you don't have significant bends.
    – Chris H
    Commented May 16, 2015 at 19:52
  • If you can, I'd suggest you inlcude some accesses, maybe one every 50m or even less, and put some kind of junction box at each one. Rationale is that some data lines may not be able to bridge 200m without some kind of amplifier/repeater(s) along the line.
    – JimmyB
    Commented May 18, 2015 at 8:45
  • 1
    @wallyk when I needed some for cable pulling in a previous job I ended up buying an equivalent from a shop describing itself as a "theatrical chandler". I think it was meant for lowering/suspending props. The censorware at that company made the usual online suppliers of paracord unreachable because they also sell "weapons"
    – Chris H
    Commented Jan 21, 2016 at 6:52

4 Answers 4

Reset to default
39

Empty conduit is your best bet here. No point in guessing what (if anything) you may get, and guessing wrong. While you can leave a pull string in it, you can also just vacuum a pull string into it when the time comes (that's what is normally done to install it in the first place). If you do leave a string, don't worry about how big/strong it is: it can be used to pull in one big/strong enough when the time comes. Do make sure it won't rot while it's waiting. And CAP THE ENDS of the empty conduit, or it may not be as empty as it should be when you need to use it.

Speaking from personal experience, assuming you don't need more than one for excessive bends/sweeps (and do use long-radius sweeps when you do need to make a bend, not the short radius stuff from home centers) you will be much happier with a pull box/hand hole/access at the halfway point.

I have hand pulled (no winch) fiber over 600 feet. It was not much fun. With correct technique (pulling on the Kevlar, not the fiber or the jacket), possible, but no fun. 330 feet/100m it should be easy (was for us) if the conduit is configured correctly (large-radius sweeps, no more than 360 degrees of bending between access points.)

Enter (and leave) the pull box with 45s, not 90s. Leave some extra cable coiled up in the pull box in case of any future need for more at either end due to damage. Before pulling cable in, see figure 8 coiling and use it so you can pull the cable in, figure 8 coil the other half, flip the coil and pull it the rest of the way - no tangles.

For political/turf (rather than electrical) reasons, it's often best to keep cable, telephone and "whatever is next" in separate conduits. It's also much less practical (or more difficult) to pull into a conduit with a cable in it - often best to remove the original cable and pull the new cable and the original cable back in together, rather than trying to pull a new cable in next to the original - but best if you can just pull the new cable in its own conduit and leave the original cable/conduit alone.

Additional suggestions -

  1. If using PVC conduit, choose schedule 80, and deburr (remove sharp inside edges from) the male ends of the joints.
  2. If you can get polyethylene conduit, consider it as you can get 100 meters with no joints and it's more flexible than PVC (effectively the same as polyethylene water pipe, with different certifications stamped on it)
  3. Do not neglect the locating/warning tape - whether it says buried fiber optic below or buried telephone line below does not matter nearly as much as that it is there in the top of the trench, directly over but well above the conduits.
Improve this answer
2
  • 1
    At least in Europe, we have flexible double-layer PVC ductwork / conduit pipes which are used a lot construction. The smooth surface of the inner layer makes pulling wire runs a treat. Different lengths allow for a jointless installation. And the stiffness of the pipe makes it virtually impossible to have a bending radius too narrow for a fibre run. adb.fraenkische.com/medien/dokumente/en_ffkus-em-f_grey.pdf There also are single-layer pipes which are not nearly as suitable, but most "highspeed" models certified for underground installations should do fine.
    – the-wabbit
    Commented May 16, 2015 at 13:00
  • 6
    "it may not be as empty as it should be when you need to use it." -- IP over rodent carrier?
    – Steve Jessop
    Commented May 16, 2015 at 15:13
13

The best future proofing you can do is over-provisioning the amount and size of conduit. Pulling a cable through a relatively straight 200m run is not out of the question especially with proper cable lubricant and a large enough conduit.

I would suggest not pulling anything like fiber without proper specs on the gear on both ends. There's a good chance you'll just be spending money for no reason, and if in 10 years time it turns out it was the wrong cable, you'll need to pull a new one anyways.

I would generally suggest placing fiber in its own conduit/raceway. It is a sensitive cable and is easy to stretch rendering it useless. When you have many cables in the same conduit, often they will twist around each other and rub against one and another when you pull them. Cables like RG6, RG11 and pretty tough compared to the type of fiber you'd likely run (I'm not talking about trans-Atlantic fiber runs with a cross section of a couple feet and heavy metal protection).

As long as you have a pull string, you can pull whatever you need in the future, when you need it.

Improve this answer
6

Could you put a couple intermediate "manholes" in the path? So instead of one 200m pull you have 3 or 4 shorter runs? You'd still run a 200m cable, but this way you only have to pull it 50-65m at a time. I'd definitely run at least one, maybe 2 empty conduits - it's a lot easier to run an extra conduit now than to re-trench it later

Improve this answer
0

The recommendation I had received was run several lengths of string along the cable run. The idea being that you can tie the string to new cable and pull it through. Obviously this only works on certain kinds of runs.

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.