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Chapter 3: Troubleshooting
70
Fiber Optic Port Link LED is Off
When a fiber optic port on the switch is connected to a properly operating
end node, the Link LED for the port should be on. If a Link LED is off, do
the following:
Verify that the end node connected to the port is powered ON and is
operating properly.
Check that the fiber optic cable is securely connected to the port on
the switch and the port on the end node.
If the fiber optic port is on a GBIC, SFP, or XFP transceiver, check to
be sure that the transceiver is firmly inserted into the slot on the switch.
Make sure that you are using the appropriate type of fiber optic cable
and that the cable length does not exceed the allowed maximum
distance. The cable specifications for the ports on the AT-9408LC/SP
Switch are listed in Table 10 on page 51. For cable specifications for
an SFP or GBIC module, refer to the installation instructions shipped
with the module.
Use a fiber optic tester to test the attenuation on the cable and the
strength of the optical signal. The operating specifications for the ports
on the AT-9408LC/SP Switch are listed in Table 16 on page 82. For
operating specifications for an SFP or GBIC module, refer to the
installation instructions shipped with the module.
Check that the operating specifications (for instance, wavelength and
maximum operating distance) of the fiber optic port on the remote end
node are compatible with the fiber optic port on the switch.
Check to be sure that the fiber optic ports on the switch and on the end
node are operating at the same speed and duplex mode.
A fiber optic cable contains two separate fiber strands. One strand is
for receiving data and the other is for transmitting data. When you
connect a fiber optic cable to a port, be sure that the receive fiber
connector is connected to the transmit connector on the remote end
node, and that the transmit fiber connector is connected to the receive
connector on the remote node.
Note
The L/A LED for an SFP transceiver slot may remain ON if you
remove the transceiver when it has a link to an end node without first
disconnecting the fiber optic cable. The L/A LED will change to OFF
the next time an SFP module is installed in the slot. To avoid this,
always disconnect the fiber optic cable before removing a
transceiver.