Well......Corning spec sheets actually have "Bend Diameter", not radius. Now that I noticed, I recall that this has tricked me before. So, we actually need about 8-1/2" radius for that 432F loose tube. That's not the worst, but still a little frustrating.
I talked to a Corning tech support person on the phone, and all he could say was that you have a risk of damaging the fibers if you bend tighter than the minimums. He said something about "snapping" the outer jacket, but I assume he means crimping it. I said I still don't see how that would hurt the fibers, and all he could add was that the risk of damage increases the more you bend it beyond the minimum radius, and the warranty won't cover it if you do. I am questioning it because it means substantially oversizing conduit and/or fittings. A 2" conduit elbow has a 9.5" radius in the center, a 432F loose tube in there would be ok with the operating bend radius, but you exceeded the installation bend radius when you pulled the cable in. So every elbow has to be a sweep and every pull box has to be 16" long. Now how do you turn through a wall? Even 2" Mogul LB's are too tight, and a JB would have to be at least 12" deep. A 3-1/2" or 4" Mogul Pulling Elbow should work (allows 10" bend radius), but those are ginormous. A standard 4" LB by the way allows a 5.5 to 6 inch bend radius. That's technically too tight even for a 144. I'm guessing most of us are just installing cables with bends tighter than the specified bend radius and nothing bad is happening. -Adam ________________________________ From: Adam Moffett <[email protected]> Sent: Thursday, June 11, 2026 2:57 PM To: AnimalFarm Microwave Users Group <[email protected]> Subject: OSP Cable minimum bend radius + bend insensitive fiber You'd be hard pressed to buy fiber that isn't bend insensitive anymore, so why do my OSP cables still have huge minimum bend radii? 5-10mm minimum bend radius on modern fiber. 16.9"(430mm) minimum bend radius on a 432F loose tube Corning ALTOS. If I used a vise to push that 432F into a hairpin turn, I'm sure it would crimp the jacket in a bad way, but it wouldn't hurt the signal. So what's the real limiting factor on the bending? [cid:a5280e86-6937-413b-81cf-4fba362da166]
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