CANOGA PERKINS 2270 Fiber Optic Modem - Manual (Page 59)

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2270 Fiber Optic Modem
Step Symptom Possible Cause(s) Action
2 (cont.) Perform the following optical loss calculation:
•
Local Receiver level minus remote Transmit level = near-end link loss figure
•
Remote Receive level minus local Transmit level = far-end link loss figure
Check the optical cable loss figure against the optical link loss budget specified in
Table 1-B for the specific fiber-optic modem. For the HP Laser version, check that the
Tx PWR and Rs SENS switches are set according to Section 1.10.3.
If the actual cable loss still exceeds the loss budget for the modem, go to Step 3. If the
cable loss is within the specified loss budget for the modem, go to Step 5.
NOTE: The link loss should be at least 3 dB lower than the loss budget speci-
fied for the modem. This design margin will compensate for LED/Laser aging
and small changes in the actual link loss.
3 Cable loss exceeds Defective F/O cable Repolish or replace
modem loss budget defective connectors
4 Cable loss exceeds Defective F/O connectors Repair or replace
modem loss budget defective cable
5 Set up BERT for the proper clocking, data rate and format as used with the circuit. Use
the existing interface cables if possible. Connect the BERT in place of the local user
device. Connect a data clock loopback connector in place of the remote user device.
Run the BERT test and go to the next step.
6 System loopback test Modem not configured Verify/correct switch and
passes but modems properly strap settings on modem
will not pass data and devices
7 System loopback test Interface cables damage Repair damaged or
passes but modems or miswired miswired cables
will not pass data
Optically loopback each modem and repeat BERT test as detailed in Step 5
8 Modem fails BERT test Defective modem or Replace defective modem
when optically looped electrical interface
back to itself