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Thread: Multi Mode Fiber for 3/4" conduit

  1. #1
    Join Date
    Feb 2003
    Location
    Bremerton, Washington
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    7,583

    Multi Mode Fiber for 3/4" conduit

    I have a ¾” rigid conduit with 5 each 12 AWG THHN/W wires, the conduit is embedded in concrete in a parapet wall on a dam.

    I would like to pull a multimode cable thru the conduit, it would need to be wet location rated, and small diameter, minimum of 2 fibers, 4 would be better.

    Does anyone make a “zipcord” type cable that is wet location rated?

    Corning has a Freedm LST cable, 2-12 fibers that is 0.31 inches diameter

    The best solution would be to run a new 1" conduit, but the parapet wall has long curves in it, and I am not sure how the conduit could be bent and assembled...no problem to put strut on the parapet wall. The total run would be about 100 ft.
    Moderator-Washington State
    Ancora Imparo

  2. #2
    Join Date
    Apr 2009
    Location
    Williamsburg, VA
    Posts
    4,127
    This is listed for wet locations:

    http://ce.superioressex.com/uploaded...IO-TB-OFNR.pdf
    Electricians do it until it Hertz!

  3. #3
    Join Date
    Mar 2010
    Location
    Lake of the Ozarks
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    975
    Pulling that fiber through 100' of 3/4" RMC with existing wires in it would make me nervous given the max pulling tension.

    #PrudentPrePlannigPreventsPissPoorPerformance

  4. #4
    Join Date
    Feb 2003
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    Existing wires would be pulled out and new MM fiber pulled in with new wires at the same time.
    Moderator-Washington State
    Ancora Imparo

  5. #5
    Quote Originally Posted by tom baker View Post
    Existing wires would be pulled out and new MM fiber pulled in with new wires at the same time.
    This is a good plan, but I still would be wary of pulling through any existing rigid that is embedded in concrete. How long has the conduit been in place? If it has been years you may find the old conducters may not even pull out without damage, let alone getting something new pulled back in. In my experience rigid has a bad habit of corroding terribly when embedded in a pour.

    100 feet isnt that far to run new, a skilled tradesman shouldn't have any issues with curves or odd angles.

    Wish I could give you a cable recommendation, a bit out of my wheelhouse. Good luck!
    son you finally got it made

  6. #6
    Join Date
    Jul 2017
    Location
    Brasher, NY
    Posts
    1
    I question the need for MMF, my personal opinion is any new installation should be singlemode fiber only.

    If you're looking for 1-2 pair, I'd consider installing 'drop fiber'. It's cheap and you could probably push it through a 100' section of 3/4 with the fiberglass member.

    If you have tight bends, you may want to go for tight buffer which doesn't have a structural membrane. I prefer loose tube FreeDM like you listed above, but you may have limitations.
    Any outdoor rated cable should be fine for water submersion.

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