Specifications
1-70
Cisco ONS 15454 Troubleshooting and Maintenance Guide
November 2001
Chapter 1 Alarm Troubleshooting
Step 5 Repeat Step 4 for all ONS nodes in the BLSR.
1.3.103 SD-L
• Not Alarmed (NA) (Condition)
Signal Degrade occurs when the quality of the signal is so poor that the bit error rate (BER) on the
incoming optical line passed the signal degrade (SD) threshold. The ONS 15454 sets the BER threshold
for SD from 10
-9
to 10
-5
. Signal degrade is defined by Telcordia as a “soft failure” condition. SD and
signal fail (SF) both monitor the incoming BER and are similar alarms, but SD is triggered at a lower bit
error rate than SF. SD causes the card to switch from working to protect.
SD-L causes a switch from the working card to the protect card at the line (facility) level. A line or
facility level SD alarm travels on the B2 byte of the SONET overhead.
The SD alarm clears when the BER level falls to one-tenth of the threshold level that triggered the alarm.
A BER increase is sometimes caused by a physical fiber problem, including a poor fiber connection, a
bend in the fiber that exceeds the permitted bend radius, or a bad fiber splice.
Warning
Invisible laser radiation may be emitted from the aperture ports of the single-mode fiber optic
modules when no cable is connected. Avoid exposure and do not stare into open apertures.
Caution Always use the supplied electrostatic discharge wristband when working with a powered ONS 15454.
Plug the wristband cable into the ESD jack located on the lower-right outside edge of the shelf
assembly.
Procedure: Clear the SD-L Condition on an OC-N Card
Step 1 With an optical test set, measure the power level of the line to ensure it is within guidelines.
Step 2 Verify that optical receive levels are within the acceptable range.
Step 3 Clean the fibers at both ends for a line signal degrade:
a. Clean the fiber according to local site practice.
b. If no local practice exists, use a CLETOP Real-Type or equivalent fiber-optic cleaner and follow the
instructions accompanying the product.
Step 4 Verify that single-mode fiber is used.
Step 5 Verify that a single-mode laser is used at the far end.
Step 6 If the problem persists, the transmitter at the other end of the optical line may be failing and require
replacement.
1.3.104 SD-P
• Not Alarmed (NA) (Condition)