How do I perform a loopback test on serial fiber communication without a fiber optic splicer?


  • How do I perform a loopback test on serial fiber communication without a fiber optic splicer/coupler?
  • Is there anyway to perform a loopback test without a patch fiber cable?


  • Serial Fiber Communication
    • Product Family: Message Displays
    • Product: Fiber Card, Signal Converter
    • Component: Signal Converter
    • Control System:


  • ​​Follow steps below to verify all components. 


  1. Follow article How do I perform loopback testing through a Gen 2 Serial Radio system?, DD2032686 To verify equipment is good up to the input of the signal converter, follow steps 1-4 of the article linked above. If loopback passes at the serial cable/serial adapter, go to step 2.

Inside at Signal Converter

    2. Hook up one fiber core to one of the TX transmits (J2 or J4) at the fiber signal converter inside.

    3. Hook up another core to one of the RX receives (J3 or J5).

  • Note: The fiber pair must be connected to either one set of outputs, J4/J5 or J2/J3. As pointed out in the left side of the diagram below.

Outside at Fiber Serial Card

    4. Hook up the fiber core that was hooked up to TX inside to the J5 RX connection.

    5. Hook up the fiber core that was hooked up to RX inside to the J2 TX connection.

   6. Perform the loopback test.


*When finished with test, return the cables to their correct positions:

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KB ID: DD2658717

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