Which of the following conditions will not trigger GPON Type B dual-homing protection switching?

Question

Options

• APrimary OLT PON failure
• BThe main optical fiber is broken
• CActive OLT failure
• DMultiple ONUs are connected to the optical splitter, and one of them is offline.

• A
  10% (5)
• B
  6% (3)
• C
  2% (1)
• D
  82% (42)

Explanation

Option D is correct because GPON Type B dual-homing protection switching is designed to protect the shared network infrastructure - specifically the OLT and the feeder (main) fiber - not individual end-device connections. A single ONU going offline affects only that terminal device and does not indicate a fault in the protected upstream path; the remaining ONUs on the splitter continue operating normally.

Options A, B, and C are all valid triggers because they represent failures in the protected infrastructure: A (Primary OLT PON failure) and C (Active OLT failure) both take down the upstream aggregation point for all ONUs, while B (main fiber break) severs the shared feeder link - all three scenarios justify switching traffic to the standby OLT to restore service for all connected ONUs.

Memory tip: Think of Type B dual-homing as protecting the "trunk of the tree" (OLT + feeder fiber). A branch (individual ONU) falling off doesn't kill the trunk, so it never triggers a trunk-level failover. If you can ask "does this failure affect all ONUs on this splitter?", the answer determines whether protection switches - a single ONU offline affects no one else, so no switch occurs.

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