Verifying GBIC and Cable Signal Presence
Verifying GBIC and Cable Signal Presence
NOTE: Do Not look directly into any fiber cable or GBIC
optical output.
To view an optical signal, use a mirror to view the reflected light.
Verifying Signal Presence: In addition to verifying
port LED status, you can verify signal presence by using a mirror to look for a
reflected light at the fiber-optic cable ends and the GBIC transmitter.
To verify signal presence at the hub end of a link, insert a GBIC into
the hub and place a mirror at the bottom of the SC connector.
If a signal is present, you will see a low intensity red light in the mirror
reflecting from the GBIC transmitter.
Verifying Node End: To verify the integrity of the
fiber optic cable at the node end of a link, make sure the cable is attached
to the GBIC at the hub and the hub is turned on.
Dual SC fiber-optic cable connectors are keyed and will insert into a GBIC in one direction only.
Place a mirror at the node end of the link. A low intensity red light is visible in the mirror
reflection of one of the SC leads, as shown in the following illustration.
If a fiber-optic cable has good transmitter output but a broken or
degraded receiver lead, the end node might sense a loop down state
Because the transmitter is good, the hub responds to the end node valid
Fibre Channel signal and adds the device to the loop. But, because the
end node is not receiving Fibre Channel signals, it will
stream loop-down sequences onto the loop. This prevents
all data communications among the devices on the loop
and will continue to do so until the condition is corrected.
Verifying Hub End: To verify the integrity of the
fiber-optic cable at the hub end, make sure the fiber-optic cable is plugged
into the host bus adapter at the host or into a disk-array controller and that
the device is enabled on the loop.
Using a mirror, examine the cable SC leads to verify that a low-intensity red light
is visible on the receiver lead.
NOTE:
Some fiber optic cables are marked with an "A" on the receiver lead and a "B"
on the transmitter lead and are keyed.
Some multimode cables plugged into a GBIC, HBA, or disk array controller are
key-oriented with the "B" lead inserted into the device transmitter.
Place a mirror on the opposite end of the cable to see the low-intensity red
light on the "A" receiver lead.
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