Watch upstream bursts propagate through a 2-stage PON tree. The OLT schedules them collision-free at its own receiver — but at any other observer, propagation delays can shuffle them on top of each other.
S1 ONTs
S2 ONTs
collision
selected
How to read it. Solid trails = main upstream signal heading to OLT. Faded trails = port-to-port leakage diverging at the LCA splitter and propagating to the observer.
Try this. Set observer to S1 → no collisions, ever. Switch to S2 → cross-subtree (S1↔S2) bursts can collide. Skew is exactly 2·(D2−D1)/c_f.
Click any ONT to select it — its transmissions show up in the bottom timeline.
Keyboard. Space = play/pause. ←/→ = step ±1 μs.
Note. All segments share one px/km scale, so photon speed and trail length are visually consistent across drops, feeder, and trunk. ONTs fan out beneath their splitter at a radius proportional to their drop length.
OLT receiver timeline (μs, OLT clock) — packed by ranging