Specifications

1-71
Cisco ONS 15454 Troubleshooting and Maintenance Guide
November 2001
Chapter 1 Alarm Troubleshooting
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-P causes a switch from the working card to the protect card at the path (STS) level. A path or STS
level SD alarm travels on the B3 byte of the SONET overhead. The ONS 15454 detects path SD on the
STS level, not the VT level.
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-P 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 Verify that single-mode fiber is being used.
Step 4 Verify that a single-mode laser is being used at the far end.
Step 5 If the problem persists, the transmitter at the other end of the optical line may be failing and require
replacement.
1.3.105 SF-L
• Not Alarmed (NA) (Condition)
A Signal Failure occurs when the quality of the signal is so poor that the BER on the incoming optical
line passed the signal failure (SF) threshold. The ONS 15454 sets the BER threshold for SF from 10
-5
to
10
-3
. Signal failure is defined by Telcordia as a “hard failure” condition. SD and SF both monitor the
incoming BER error rate and are similar alarms, but SF is triggered at a higher BER than SD.
SF-L causes a switch from the working card to the protect card at the line (facility) level. A line or
facility level SF alarm travels on the B2 byte of the SONET overhead.
SF causes a card to switch from working to protect at either the path or line level. The SF 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.