atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring Fiber bend radius

Got a potential job to run a six strand MM 62.5
pre connectorized fiber. Overall length app. 600' mostly inside building. Met with the electrical contractor who will be installing
1 1/2" PVC conduit and he asked if I wanted LBs or sweeps (at least 10- 90 deg. turns in total run) and I specified sweeps.That got me to thinking a bit about pull points and that maybe LBs would make it easier.My question is with a
1 1/2" conduit having LBs is the radius too tight
for fiber? As always, thanks for your help and advice.

According to BICSI, Conduit runs exceeding 100ft length should not have any more than 2 90 degree bends. If Conduit requires more than 2 bends, then a pull-point should be installed. A pull-point can be defined as an LB, however, there is a particular type of LB specifically for fiber optic. Do not use the standard LB found at Lowes or etc. The standard LB internally makes a sharp 90 degree bend posing potential bend radius violations which could cause potential breakage during pulling of the fiber.

LBs may certainly be too tight. You can check with the fibre manufacturer- their website should list the bend radius. I always found that 1.5" was perfect - there were never any bend issues.

Sam

has he installed the conduit yet? If not, there is a option to do the newer armoured interlocked fiber. Several makers have it. It is installed in place of having to install conduit or interduct. We just used some a month ago and it worked great. It looks like orange electrical flex, but with fiber in the middle. It was not that expensive either. If you buy the good MM fiber with the kevlar strands, you can make quite a few long sweeps without any issues. For grins, I would out a 1x1 PB halfway, just to be safe.

Sweeps with pull boxes.

Thanks guys, appreciate the input. Think sweeps are the right way to go.

The NEC (whose rules do not apply to this, but is still good common sense) calls for a pullbox or at least a "C" condolet every 100'. Besides making it easier to fish the cable in, it makes pulling the cable in easier and puts less stress on it.

Sam

The bend radius is ten times the diameter.

Make sure you get the fiber assembly built with a pull sock. We do that for ALU all the time.

Before the pull take a loss reading of each fiber and record it. Immediatley after the pull take another reading of the loss of each fiber and compare. Test all fibers do not assume that if one is good they are all good. Make sure the fiber connectors covers are in place before and after the pull.