Additional Service Information; Applications And Configurations; Verifying Signal Presence; Verifying Node End - IBM TotalStorage DS4000 Hardware Maintenance Manual

Figure 2. Verifying signal presence

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 Figure 3.
Connector
Figure 3. Verifying node end
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

Additional service information

This section contains additional service information for the fibre channel hub.

Applications and configurations

The fibre channel hub modular interface provides flexibility and is upgradable to
available short-wave and long-wave optical fibre channel product port interfaces.
Keys
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.
Chapter 2. Type 3523 Fibre Channel Hub and GBIC
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