CANOGA PERKINS 2240 Fiber Optic Modem - Manual (Page 86)

2240 Fiber Optic Modem User Manual Chapter 5 Troubleshooting
Local and Remote Loopback
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When activated, the Local Loopback test will cause all data transmission from the near end
(local) user device to be looped back toward the receive of that same device. The data from the
remote user device will not loop back (it will continue receiving data from the local device), but
the Loop On indicator at the far end turns on.
The loopback point is set at the electrical interface of the local modem (see Figure 5-1).
NOTE: If the local loopback modem is operating in Mode 5 (slave clock mode),
the remote device will receive garbled data because of the overall timing
configuration. The local loopback will function correctly.
5.2.2 Remote Loopback Test
When activated, the Remote Loopback test will cause all data transmission from the near end
(local) user device to be looped back after the optical sections of the remote device.
The data from the remote user device also loops back locally at the electrical interface. See
Figure 5-2.
Figure 5-2 Remote Loopback from User End of Fiber Link
HOST
TERMINAL HOST
TERMINAL USER
TERMINAL
TX
RX
RX
TX
LOOP
ON
LOOP
REMOTE
SYNC
SYNC
LOOP
OFF
LOOP
ON
FIBER OPTIC LINK
REMOTE
LOOP