Swapped a 12‑strand trunk to a new 45U rack this morning and now I’m seeing 1.2–1.5 dB bounce at 1310 on two LC pairs, OTDR flags events about 8–10 m from the panel. Anyone run into vertical cable manager pressure causing intermittent microbends, or should I be hunting a cranky MPO cassette or a too-tight radius on the overhead tray? Looking for a sanity check before I pull and re-dress, then re-test with iOLM.
I’d pop the vertical door and loosen any ties, then re-shoot — if the “8–10 m from the panel” bump shifts or shrinks, it’s manager pressure or that first overhead turn (think garden-hose kink). Also fire a trace at 1550: if the spike grows it’s a bend; if it’s the same, reseat or swap the MPO cassette. Does your 10 m mark land right at the first 90 on the tray?
Quick check: shoot those fibers at 1550 and then from the far end — if that 8–10 m blip gets worse at 1550 and triangulates to the same spot, it’s a bend/pressure point; if it doesn’t, swap the MPO cassette with a known-good and see if the bounce follows. @pcarter51’s tie-loosen is good because 1550 is a bend’s lie detector — did the trunk take a twist at the first ladder turn?