Cisco ONS 15454 SDH - Page 138

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Cisco ONS 15454 SDH Troubleshooting Guide, R5.0
July 2005
Chapter 1 General Troubleshooting
1.12.2 Faulty Fiber-Optic Connections
Step 2 Ensure that the connector keys on the SC fiber connector are properly aligned and locked.
Step 3 Check that the single-mode fiber power level is within the specified range:
a. Remove the Rx end of the suspect fiber.
b. Connect the receive end of the suspect fiber to a fiber-optic power meter, such as a GN Nettest
LP-5000.
c. Determine the power level of fiber with the fiber-optic power meter.
d. Verify the power meter is set to the appropriate wavelength for the optical card being tested (either
1310 nm or 1550 nm depending on the specific card).
e. Verify that the power level falls within the range specified for the card; see the “1.12.3 Optical Card
Transmit and Receive Levels” section on page 1-143.
Step 4 If the power level falls below the specified range:
a. Clean or replace the fiber patchcords. Clean the fiber according to site practice or, if none exists,
follow the procedure in the Cisco ONS 15454 SDH Procedure Guide Chapter 15, “Maintain the
Node.” If possible, do this for the optical card you are working on and the far-end card.
b. Clean the optical connectors on the card. Clean the connectors according to site practice or, if none
exists, follow the procedure in the Cisco ONS 15454 SDH Procedure Guide Chapter 15, “Maintain
the Node.” If possible, do this for the optical card you are working on and the far-end card.
c. Ensure that the far-end transmitting card is not an ONS 15454 SDH IR card when an
ONS 15454 SDH LR card is appropriate.
Note IR cards transmit a lower output power than LR cards.
d. Replace the far-end transmitting optical card to eliminate the possibility of a degrading transmitter
on this optical card.
Caution Removing a card that currently carries traffic on one or more ports can cause a traffic hit. To avoid this,
perform an external switch if a switch has not already occurred. See the “2.10.2 Protection Switching,
Lock Initiation, and Clearing” section on page 2-260 for basic instructions. For detailed information,
refer to the Cisco ONS 15454 SDH Procedure Guide Chapter 15, “Maintain the Node.”
e. If the power level still falls below the specified range with the replacement fibers and replacement
card, check for one of these three factors that attenuate the power level and affect link loss (LL):
• Excessive fiber distance; single-mode fiber attenuates at approximately 0.5 dB/km.
• Excessive number or fiber connectors; connectors take approximately 0.5 dB each.
• Excessive number of fiber splices; splices take approximately 0.5 dB each.
Note These are typical attenuation values. Refer to the specific product documentation for the
actual values or use an optical time domain reflectometer (OTDR) to establish precise link
loss and budget requirements.
Step 5 If no power level shows on the fiber, the fiber is bad or the transmitter on the optical card failed.
a. Check that the Tx and Rx fibers are not reversed. LOS and EOC alarms normally accompany
reversed Tx and Rx fibers. Switching reversed Tx and Rx fibers clears the alarms and restores the
signal.