N10-005 · Question #858
A technician is not getting a link light on two switches connected by a fiber cable. After the cable tests good, which of the following should the technician check NEXT?
The correct answer is C. TXRX reversed. Fiber optic connections require that the transmit (TX) strand on one end connects to the receive (RX) strand on the other. If both ends are wired TX-to-TX or RX-to-RX (a crossover error), no link can be established even though the cable itself is physically intact. Since the…
Question
A technician is not getting a link light on two switches connected by a fiber cable. After the cable tests good, which of the following should the technician check NEXT?
Options
- AOpen shorts
- BExcessive DB loss
- CTXRX reversed
- DSplit cables
How the community answered
(22 responses)- A5% (1)
- B5% (1)
- C77% (17)
- D14% (3)
Explanation
Fiber optic connections require that the transmit (TX) strand on one end connects to the receive (RX) strand on the other. If both ends are wired TX-to-TX or RX-to-RX (a crossover error), no link can be established even though the cable itself is physically intact. Since the cable already tested good, a reversed TX/RX pair is the next most likely culprit. Open shorts and split cables would have been caught by the cable test; excessive dB loss is possible but less likely than a polarity reversal.
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