sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring Fiber bend radius

I know the minimum bend radius is specified by manufacturer. However, I need to plan for some underground boxes now without knowing what brand will be used. The specs call for 3x3x3 underground boxes. Is that safe to assume any 12 pair MM cable will be OK with that? I will be subbing the innerduct and fiber install to a specialist but at the moment I have nobody in mind. I just want a general idea so I can say the boxes would be OK as spec'd. If we need bigger boxes it needs to be done asap.

On one run it will have to make a 90 out of the box, go up a outside wall in wall in conduit then make another 90 then yet another 90 down into an equipment room. The specs don't include an inside box, should I plan on using one or would a 3 foot diameter service loop suffice?

What would the tightest loop diameter be that would be safe for any brand?

Question, can you pull a cable, any cable let alone fiber in a 3x3x3 box? My hand barely fits a box like that.

I suggest that you have pull points at those 90's the cable is not going to move well without them.

The loop will not be your problem. The hard kink on the cable while pulling will be your big issue.

Service loops? thats a pref and I like 15 feet on each end.

I meant to say 3 feet by 3 feet by 3 feet in te ground. I am not sure what size we'd need in the ceiling. That is why I asked about the minimum loop diamater. Back in the day, 1991 to be exact, I recall we needed some pretty big boxes for loops and bends. But I seem to recall that was more for the fact that the heavy plastic jacket couldn't bend well. Fiber has changed since then.

A 3 foot box is plenty of room, and for the ceiling you could use the same. I don't think you need the box to be 3 feet deep, a foot is plenty deep.
How much fiber do you plan on puting in? If your going to put just a 12 pair in, then a foot deep would be plenty for your under groud boxes.

Our rule of thumb used to be 1.25" conduit for 12 strand, because the bend ratio was perfect for it. With 1" the bend was theoretically too tight. A 3' box is probably overkill, even for loose tube (outdoor) fiber.

Maximum pulling strength is important too. We used to put breakaway swivels on the nose of long outdoor pulls.

Sam

I'm anticipating innerduct in the conduit. However that will be determined by the sub. We aren't set up for pulling fiber at this time plus we don;t have a verifier. I am preparing a quote as we speak for that as well as all the premise wiring and phone switch relocation. I'm going to make another post to see if somebody here is local and might want to quote the sub work.

Sam - cool. So if they intend to use 2 inch conduit then if they employ the manufacturer recommended elbow components then they are sure to be safe for any brand of fiber on the market? Is that a safe bet?

I would think that 2" conduit would be perfectly safe for any brand of 12 strand on the market. We used to run 2" for 72 and I believe even 96 strand without a problem. (Though most of what we ran was ribbon).

Sam

You don't need to put inner duct in the conduit, now that is a over kill. Inner duct is not for protection, only for identification purposes.

We used to put a kind of sleeving in the pipe. I forget the name, but it had 3 or 4 separate sections, each with its own drag. It allowed you to go back in and pull additional runs into the same conduit without damaging the earlier pulls.

Before that stuff came out, we used to pull 3, 1" innerducts into a 4" conduit.

Sam