Troubleshooting Guide

• For long fiber links, the transmit and received power are similar (after taking into
consideration connection losses and fiber attenuation).
Large differences can mean a damaged fiber or dirty or faulty connectors. Large differences
can also mean that the link does not use the right type of fiber (single mode or multimode). If
the receiver power is measured to be zero, and the link worked previously, it is probable that
the far-end transmitter is not operating or the fiber is broken.
6. Compare the measured receive power for the near-end optical device to the measured
receive power for the far-end device.
Large differences could mean that the optical devices are mismatched (that is, -SX versus -
LX). If optical devices are mismatched, the receiver can be saturated (overdriven).
7. If a receiver is saturated but still operable, install a suitable attenuator.
For long-haul optical devices, the receive power must be significantly less that the transmit
power.
8. To help debug the link, loop back the local transmit and receive ports, and use the DDM
parameters to help determine the fault.
Troubleshooting fiber optic links
January 2017 Troubleshooting 143
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