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Cisco ONS 15327 Troubleshooting Guide, R3.4
April 2003
Chapter 1 General Troubleshooting
Fiber and Cabling
c. Determine the power level of fiber with the fiber-optic power meter.
d. Verify that 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 “1.8.2.3 Optical Card
Transmit and Receive Levels” section on page 1-77.
Step 4 If the power level falls below the specified range:
a. Clean or replace the fiber patch cords. Clean the fiber according to site practice or, if none exists,
follow the procedure in the Cisco ONS 15327 Procedure Guide. If possible, do this for the OC-N
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 15327 Procedure Guide. If possible, do this for the
card you are working on and the far-end card.
c. Ensure that the far-end transmitting card is not an ONS intermediate-range (IR) card when an ONS
long-range (LR) card is appropriate.
IR cards transmit a lower output power than LR cards.
d. Replace the far-end transmitting card to eliminate the possibility of a degrading transmitter on this
card.
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.
b. Clean or replace the fiber patch cords. Clean the fiber according to site practice or, if none exists,
follow the procedure in the Cisco ONS 15327 Procedure Guide. If possible, do this for the card you
are working on and the far-end card.
c. Retest the fiber power level.
d. If the replacement fiber still shows no power, replace the optical card.
Step 6 If the power level on the fiber is above the range specified for the card, ensure that an ONS long-range
(LR) card is not being used when an ONS intermediate-range (IR) card is appropriate.
LR cards transmit a higher output power than IR cards. When used with short runs of fiber, an LR
transmitter is too powerful for the receiver on the receiving card.
Receiver overloads occur when maximum receiver power is exceeded.
