Allied Telesis CentreCOM AT-MR118FT User Manual page 25

Troubleshooting
On a fiber optic segment, if the Link indicator is not
illuminated or data packet traffic is disrupted
1. Check that the fiber optic Link indicator is illuminated on both ends of the
fiber optic link.
2. Be sure the receive fiber is connected to the remote transmit port and the
transmit fiber is connected to the remote receive port. If in doubt, it does no
harm to reverse the two fibers. Check if the Link indicator is illuminated.
3. Check that the fiber optic transmit and receive ports are functioning by
installing the AT-MR118FT or AT-MR128FT in place of another fiber optic
repeater that is known to work. Check if the Link indicator is illuminated.
4. Check the fiber optic cable itself by swapping a fiber optic repeater that is
known to work for the AT-MR118FT or AT-MR128FT. Check if the Link
indicator is illuminated.
Do not attempt to use the fiber optic micro repeater as a light source
Note
with the following test. The light power varies with the duty cycle and
packet rate.
5. Determine that the losses in the fiber optic cable transmit and receive fibers
are within the flux budget of the micro repeater. This task requires a fiber
optic power meter to measure the actual loss on the fiber optic link cable. To
be within IEEE specifications the measurement must be at least -32.5 db.
The fiber optic cable must be 50/125, 62.5/125 or 100/125 micron multimode
fiber. The maximum cable length is 2,000 meters (6,560 ft.).
On a 10BASE-T UTP port, if the Link indicator is not
illuminated or data packet traffic is disrupted
With 10BASE-T Ethernet, most problems are with the UTP wiring.
1. Check that the UTP cross-over switch is properly set.
Changing the MDI/MDI-X switch or swapping cross-over to straight-
Note
through cable or vice versa to determine which is correct will not cause
any harm.
For repeater-to-10BASE-T hub connections, use a cross-over cable or set
the switch to the MDI position. For connecting a repeater to a 10BASE-T
transceiver or Network Interface Card (NIC) use a straight-through cable
or set the switch to the MDI-X position.
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